there is scarcely a harbour or river in scotland about which, at some time, mr. stevenson was not asked to give his advice. his opinion was also sought in england and ireland, and he executed works of greater or less extent in many of the cases in which he was consulted.
we may select from his reports the names of dundee, aberdeen, peterhead, stonehaven, granton, fraserburgh, ardrossan, port-patrick; the rivers forth, tay, severn, mersey, dee, ribble, wear, tees, and erne, as among some of the many places in the united kingdom where he was employed.
in a subsequent chapter extracts will be found illustrating mr. stevenson’s views on various professional subjects, and from these it will be seen that he brought his large experience and study of the waves to bear advantageously and practically on his harbour engineering. he was, as will be gathered from the extracts, at an early period fully alive to the value of spending basins for tranquillising a harbour, and of the proper disposition of the covering piers, in reference to the line of exposure, so as to avoid throwing sea into the131 harbour’s mouth, or causing it to heap up on coming in contact with the piers; while, as regards rivers, he was no less alive to the value of backwater in keeping open estuaries, and to the necessity of removing all obstructions to the free flow of the tide in river-navigation.
at an early date, for example, mr. stevenson and mr. price were jointly consulted as to the navigation of the tees, and i am indebted to mr. john fowler of stockton, the engineer to the tees navigation, for the following statement as to the result of that joint reference:—
“the navigation company consulted mr. stevenson and mr. h. price, who differed in opinion as to the general treatment of the river. mr. price recommended that it should be contracted by jetties, and mr. stevenson that the banks should be faced with continuous walls, stating as his reason for this recommendation, that ‘to project numerous jetties into the river, i regard as inexpedient, being a dangerous encumbrance to navigation, and tending to disturb the currents and destroy the uniformity of the bottom.’ the plan adopted by the navigation company was, however, that of mr. price; and jetties were constructed on the river to a large extent,” and mr. fowler adds, that “after a trial of twenty-seven years it was found that they were liable to all the objections that had been urged against them by mr. stevenson.”
accordingly, under mr. fowler’s direction, the whole of the jetties have been removed.
one of the early harbour schemes in which my father132 was engaged in england, was a harbour at wallasey pool, on the mersey, in which he acted in conjunction with telford and nimmo. the following reports will show the nature and extent of work then contemplated as a commencement of the birkenhead docks, now so valuable an adjunct to the port of liverpool. but at the early period of 1828, when the reports were written, the public were not prepared to entertain a scheme of improvement based on so great a scale. it included, as will be seen, not only the formation of a floating harbour at wallasey on the mersey, but the construction of a harbour at helbre on the dee, with a connecting ship canal between the two estuaries.
“to the subscribers for the proposed wet docks at wallasey pool.
“preliminary report of robert stevenson and alexander nimmo, civil engineers, on the proposed improvements at wallasey pool.
“liverpool, feby. 23, 1828.—having been requested to examine the situation of the wallasey pool with a view to discover how far additional accommodation might be obtained there for the increasing trade of the port of liverpool, we did accordingly meet at woodside on the 10th february 1828, and after examining the pool at high and low water, and the action of the tides on the northern edge of the leasowe level, which we found to be overflowed at high water of the 16th and 17th and 18th february, with off-shore winds and moderate weather, we next examined the shore down to low water in that place called mockbeggar wharf, which we found to consist of turf and soft marl over a bottom of fine clay. we afterwards visited the western part of the level, which extends to the immediate vicinity of the estuary133 of the dee, part of which we examined, also helbre, hoylake, and the rock channels, and directed certain surveys and levels to be taken for our further information, and though we have not yet obtained all the data requisite for forming estimates of the expense of improvement, we are generally of opinion as follows:—
“that this situation of wallasey pool affords, beyond doubt, the most favourable position in the vicinity of liverpool for an extension of the accommodation of the shipping trade of the port, at a very moderate expense.
“the ground being level, the soil water-tight and of easy excavation, docks may be formed there of any extent. the bay in front between seacombe and woodside, though mostly shallow at present, affords the first place of shelter within the mersey, and small vessels lie there out of the stream in perfect safety. it possesses a creek or channel which could easily be enlarged and deepened so as to form an outer tide harbour similar to the original harbour of liverpool, but upon a greater scale, and for the scouring of which it would be easy to open up the tide in the pool to the extent of 250 acres, as far as viners embankment, and above that to any extent that may be thought desirable. this space having a deep creek through its whole extent forms a complete half-tide basin for facilitating the entrance into the docks on either side, while on the shallow parts may be formed extensive timber-ponds. works of masonry in this situation being out of the sea-way and of the stream of the tide, may be constructed with great economy; good building stones are to be found at bidston hill, and the whole soil is a brick earth.
“the situation possesses other advantages of access not so obvious, but which may eventually be of the greatest importance. the leasowe level at the head of this pool extends as far as the river dee, and touches the sea-shore at mock beacon, where indeed it is occasionally overflowed by the tide. in this direction it would be quite practicable to open a direct passage for ships into134 the horse channel, by excavating in marl and clay, only quite clear of the shifting sands which are found in all other parts of the mersey and dee. and towards the dee a ship canal may easily be cut with its entrance either at dawpool in hoylake, or in a tide harbour which could be formed at helbre, a position which affords many maritime advantages.
“that position has several good anchorages in its vicinity, three different passages to sea, and is only five miles from the floating light, the distance of which from liverpool by wallasey and helbre is exactly the same as by the rock channel; and nine miles of it would be inland navigation, instead of an intricate passage among sandbanks, the whole of which inland navigation is an addition to the floating harbour.
“having thus briefly shown the facilities possessed to seaward, we may next turn our attention to those connected with the inland navigation. it is evident that to the ‘flats’ which navigate the duke’s canal, mersey and irwell, ellesmere, sankey, and weaver navigations, wallasey pool is just as accessible as the docks of liverpool, while by a canal to helbre you communicate with the large navigation of the dee, and the valuable mineral county of flintshire; and if ever, as is extremely probable, the canal navigation should be brought nearer to liverpool, the natural termination would be tranmere or wallasey pool, between which a cut can be easily formed. by this means boats from the small canals in staffordshire and the other inland counties can be brought down to the seaport and return their cargo without the trouble of transhipment,—an object, as being important to the proprietors of these canals, that there can be little doubt of their endeavouring to carry it into effect whenever the shipping can be accommodated on the cheshire side.
“although in the present state of our survey, and until we meet our eminent friend and colleague mr. telford, we are not prepared to enter into any detail of plans or estimates of the135 expense of these improvements, yet we are satisfied he will agree with us in opinion that the cost of even the most expensive will be greatly inferior to that of obtaining any important additional accommodation upon the liverpool shore, which being almost entirely occupied already, we consider it impossible to obtain there at any expense sufficient room for the increasing trade; and we would conclude this preliminary report by recommending to the thriving and enlightened community of liverpool to weigh well the advantages above alluded to, and the benefit of now extending their operations to the cheshire shore.
“robert stevenson.
alexander nimmo.”
“intended ship canal between the rivers dee and mersey.
“the report of thomas telford, robert stevenson, and alexander nimmo, civil engineers, recommending two extensive new sea ports, etc., on the rivers dee and mersey, adjacent to liverpool, with a floating harbour or ship canal to connect them.
“the undersigned, having so far completed their land and water surveys as to enable them to speak with confidence upon the practicability of extending the accommodation for shipping to suit the rising demands of this great commercial emporium, beg leave to commence their report upon this important subject by describing the general outline of the proposed improvements, and then to proceed to discuss them in detail; but previous to this it is necessary to make a few preliminary remarks.
“on the estuaries of the dee and mersey.
“in one or other of these must always continue to be the great port of the north-west of england, the preservation and improvement of which has become the more important since this last136 century has added so much to the progress of manufacturing and commercial enterprise, and to that extension of inland navigation, which has rendered liverpool not only the great mart of the north-west of britain and of all ireland, but nearly of the whole western world.
“the chief feature of these estuaries is the extensive range of sandbanks in their front, through which an intricate ship-navigation has to be carried. these channels have been always subject to variations, and are now only safely navigated by a careful system of pilotage.
“in the progress of our investigations, and feeling the great importance of the measures we are about to recommend, we have carefully inquired into the various changes which have taken place on these banks, as far as can be collected from history or inferred from observation, in order to be enabled to judge what is likely to take place as to their future permanent condition.
“in the time of the romans the ribble seems to have been the chief port of this district, and ribchester is said to have been a city as great as any out of rome; the port was poulton below preston, at the neb of the naze, so vastly inferior at the present time to various situations on the mersey and the dee that it is impossible not to admit that some extraordinary change has taken place in their physical condition since that period. tradition says that the port of the ribble was destroyed by an earthquake, and also that there were tremendous inundations in cheshire and lancashire about the termination of the roman sway in britain; and various phenomena we have seen seem to point to some such catastrophe.
“it is well known that in the saxon times the river dee was an important navigation, and that chester was then and for many ages after the great port of the west, and for the connection with ireland, whilst the mersey was little known, and liverpool only a fishing village.
137 “but in after times the port of chester was so much obstructed by sandbanks in the upper portions that the city became inaccessible to vessels of large draught, and though serious efforts were made to remedy this evil, and have even partly accomplished it, yet the trade of the country was gradually transferred to liverpool on the mersey, which had become a place of considerable importance at the time of the revolution, and had been created an independent port: before, it was only a creek of chester.
“in our inquiries into the early state of the navigations of the dee and mersey, the oldest chart we have found of any authority is that of grenville collins, in 1690. it is dedicated to king william, to whom he acted as pilot on his expedition to ireland; and as that army embarked from hoylake, as also that of the year before under general schomberg, and as collins was officially employed in making charts of the coast, there can be no doubt that, though rude, it conveys, as far as it goes, an authentic representation of the state of navigation at that time.
“the roadstead of hoylake was then spacious and deep, with five fathoms into it, and seven fathoms inside, from one half to three quarters of a mile wide, and covered by the hoyle sand, which was then one solid bank without any swash or opening across it, and was dry at neap tides as far as opposite the point of air and beyond.
“the dove point then projected a mile and three-quarters from the shore, separating hoylake from the rock channel, which was then nearly dry at low water as far as mockbeggar, between which and burbo sand there was only one quarter fathom, and between dove point and burbo only two fathoms.
“the large vessels which at that time belonged to liverpool put out part of their lading in hoylake until they were light enough to sail over the flats to liverpool.
“the union of hoylake and the rock channel formed, as at present, the principal passage to sea, called the horse channel, then138 a fair opening with three to seven fathoms, but considerably to the eastward of the present channel of that name; for collins’s sailing mark through it was mockbeggar hall upon the banquetting-house in bidston, would mark the present spencer’s gut as having been the channel. the north spit did not then exist, or rather was part of the hoyle bank; and the beggar’s patch seems to have been the extremity of dove point. the formby channel was said to have three fathoms on the bar, but was not buoyed or beaconed, therefore not used.
“the chester bar had nine feet least water; and wild road is marked as good anchorage, much used in the coal trade. about 1760, published in 1776, we have the survey of mackenzie, who was employed by the admiralty to make charts of the western coasts of britain, which are still in high reputation.
“at this time hoylake continued to be a good roadstead, though greatly altered; the depth at entrance was only two fathoms, eight fathoms in the middle, the width only three furlongs, and its length had diminished at least a mile. a passage was opened from the rock channel across to dove point into hoylake, and across the east end of hoyle sand, with four to eight fathoms, forming the present horse channel.
“on this chart we also perceive the beginning of another opening across the hoyle sand, now called helbre swash, then dry at low water at each end, having three fathoms in the middle, now a deep and fair channel with seven to nine fathoms, and two and a half least water at its mouth.
“since the opening of this channel or swash little or no tide sets through the hoylake, which is gradually closing up, and now used only for small craft.
“the existence of hoylake was of material importance to liverpool and also to the dee, for vessels could run there at any time; the entrance to it was marked by leading lights in the middle of last century, one of the first applications of reflecting lights to the139 purposes of navigation; they are now of little use, as the sand has shifted to the eastward, and the entrance is nearly dry at low water.
“the rock channel seems to have undergone a very important change by the time of mackenzie’s survey. we have observed that in collins’s time, 1690, it was dry at low water as far nearly as mockbeggar. although this is still nearly the case at the perch at low tides, it is opened below that in a material degree. in the space of seventy years the channel had deepened to have three or four fathoms in wallasey hole; also between mockbeggar wharf and the north bank, which was dry at low water; and a channel had opened across dove point, with two and three fathoms, into hoylake, and from thence across the east end of hoyle, forming the present horse channel, as before described, with four to eight fathoms out to sea. on the other hand, the sand from this deepening had been carried down to seaward, forming a complete shoal across the original horse channel of collins’s time, in whose sailing-line is marked a depth of four feet only, and this shoal connected with that called the beggar’s patch, and thence with the spit or flat along the west side of the horse channel, on which was six feet water. this last channel was direct and fair, with five to eight fathoms, and previous to the publication of mackenzie’s chart, but after the time of his survey, was marked by two lighthouses at leasowe shore, and subsequently by that on bidston hill under the direction of captain hutchinson, as was also the entrance into hoylake by the two lights near meols, as before described.
“the formby channel is marked as deep upon mackenzie’s chart, with four fathoms at the entrance, and between taylor’s bank and middle patch two fathoms; there is now only five feet over the flats at low water at its entrance, and it was buoyed in at mackenzie’s time; but, though the deepest channel to liverpool, it is, from its intricacy and instability, still very little used for navigation.
140 “lieutenant evans published a survey of the liverpool and chester rivers, with a book of sailing directions, which is in good repute. we have preferred the chart by mr. thomas in 1813, made by order of the lords of the admiralty, for the purpose of comparison with the several before mentioned surveys, as more minute in detail.
“at the time of this survey, fifty years after that of mackenzie, hoylake had diminished in breadth to one furlong; the depth at the entrance was three to seven feet; four fathoms near the red stones; since that time it is still shallowing, and now may be walked across at low water, from dove point to east hoyle; so that this roadstead may be considered as lost.
“helbre swash had opened to half a mile wide, with six or eight fathoms water, but with a shoal at its entrance of one fathom; there are now two fathoms and a half through that entrance.
“the brazil or north bank had extended dry, at low water, as far as spencer’s gut buoy, and the north spit or four feet flats had extended into the horse channel across the line of sea lights, thereby forcing that channel further into hoyle bank. the lower part of the rock channel had enlarged by the formation of a passage on each side of the beggar’s patch.
“the entrance to formby channel had very much altered since mackenzie’s time, and, though better marked, still continued to be little frequented. the floating light placed opposite helbre swash and the horse channel, outside of all the banks, has made a great improvement in the access from the seaward in that direction.
“the rock channel, from these circumstances, continues to be the main passage to and from the harbour of liverpool, but it is only provided with day marks, and though well buoyed cannot be navigated by night; being very narrow, and having banks in its middle, it is difficult for vessels to beat through with foul winds in one tide, and as there is no secure anchorage, frequent delays and losses take place in this part of the navigation.
141 “within the harbour of liverpool or in the river mersey the principal places of anchorage are—
“1st, abreast the town.
“2d, off the magazines, which is used by the outward-bound vessels.
“3d, up the river in sloyne roads, or broombro pool, which is almost confined to vessels under quarantine.
“in the two first-mentioned anchorages a great sea tumbles in, with ne. gales, and this, with the rapid tide and bad holding ground, causes vessels to drift, even with two anchors down, so that it is necessary for all the merchant vessels, as soon as the tide serves, to proceed into dock and remain there until a favourable opportunity occurs of putting to sea, so as to get through the rock and horse channels with daylight; hence a considerable accumulation of vessels within the docks at all times, but especially when there has been a continuance of northerly and westerly winds, and which has made it necessary to look now for additional accommodation on the opposite shore of wallasey pool.
“proposed establishment at wallasey.
“small craft find good shelter on the banks at the mouth of wallasey pool, being there out of the stream, and land-locked by the point of seacombe.
“the steamers also, to which dispatch is of moment, moor along this shore, and if there was more room in wallasey pool it would decidedly be the best anchorage about liverpool.
“wallasey creek runs nearly for two miles from the mersey, where it is stopped by an embankment, through which the waters of 3000 acres of marsh land pass by a tunnel. the pool below the embankment covers nearly 250 acres at spring-tides, and by its backwater maintains a channel through the creek down to low water springs, and with seventeen feet at high water springs as far up as the embankment.
142 “previous to the embankment it is certain that this creek was materially deeper. on mackenzie’s chart, opposite to its mouth, there are twenty fathoms marked, being much more than anywhere within the mersey at present, and a bottom of rock. this channel would therefore be restored by any considerable addition to the backwater; and at all events, if the lower parts of the creek were opened by dredging, and, by a power of scouring it, low water obtained, a safer inlet for vessels to run to would be acquired than at present exists anywhere in the neighbourhood of liverpool.
“on the south side of the creek, between woodside ferry and bridge end, there is a bottom of sandstone rock, but this ceases at bridge end creek; and above that place the shore is composed of firm clay, fit for brick making, to a depth at least of thirty feet, in which excavation for docks and basins could be carried on with great facility.
“upon the attention being directed to wallasey pool as a commercial station, it will appear at first view obvious that an entrance might be made along the low ground which extends from it to the sea shore at leasowe, by which a direct passage to sea might be obtained, and the insecurities and dangers of the bar and banks of the rock channel be avoided; but the objections to such an entrance are, that the channel outside affords no safe anchorage, and the cut would be exposed directly to the stroke of the sea, and if protected by piers their construction would not only be expensive, but might also materially alter the channel along shore.
“but the ground continues equally favourable to the westward as far as hoylake and the dee below the hill of the grange. the shore is skirted by a narrow belt of sandhills, through which however there would be no great difficulty in making a passage into the tideway. here it is important to remark that the helbre swash opens a deep and fair channel, well sheltered by banks on each side, and only five miles in extent to the floating light, which is in a direct line with it.
143 “this channel has been formed within the last century, and readily accounts for the deterioration of hoylake; it now carries down most of the ebb of the dee, and is likely to improve still more, having deepened materially since thomas’s survey in 1813.
“through all the vicissitudes we have traced there has been deep water and good anchorage at the point of helbre island; and as that situation affords solid rock for every sort of construction, there can be no risk of the permanency of any work that may be established there.
“sea-locks constructed at helbre would be protected against the prevailing westerly gales by the island itself, against the northerly by the bank of east hoyle; and they may be connected to the mainland by banks formed across the strand, which is mostly dry at high water of neap tides; and by means of these banks a pond of sixty-four acres may be enclosed, which, being filled at spring tides, may be employed for the purposes of scouring and keeping open the harbour and its entrance, and as a reservoir for a ship canal from thence to the shore, and along the low ground to wallasey pool. such a canal, of large dimensions, and seven miles long, will be one continued floating harbour, which may be carried to a great extent in various directions and on the same level.
“independent of helbre swash two other channels for ships passing to sea unite at that position; one, the original hoylake, still sufficiently navigable at high water; the other, the passage by wild road and chester bar, greatly superior in safety and permanency to that of the formby channel; for in all the successive charts little or no change seems to have taken place on that bar, which continues to have nine feet at low water, with a rise of thirty. the great extent of ebb-tide from the dee (being quite as extensive an estuary as that of the mersey) must always keep one or other of those channels or all of them open, so that ships may sail from helbre in almost every wind; and if necessary to beat144 out, a vessel starting from helbre with the first of the ebb down the swash will be at the floating light and clear of the banks before another from liverpool can get round the rock perch.
“to persons at all acquainted with the navigation to liverpool it must be quite unnecessary to point out the benefit of this proposed arrangement, which, while it preserves all the advantages of communicating with the mersey, and the extensive inland navigations connected therewith, affords a new passage to and from the sea, by means of the dee, by which both the distance and dangers of an intricate navigation will be wholly avoided.
“an important advantage obtained by this plan is, that the proposed entrance at helbre is within the jurisdiction of the port of chester, of which it is recorded as a creek in sir matthew hale’s treatise de portibus maris; and business done there or upon its waters, even as far as wallasey pool, being within the port of chester, will have to pay the dues at that port; and unless ships and goods lock into the mersey they are exempted from the dues of liverpool. the facility of construction is so great that a moderate charge for dues will be a sufficient remuneration for the capital required. the ground on either side of the canal is singularly suitable to be appropriated to any kind of establishment connected with shipping, and there can be no doubt that it will be so employed even by private speculation; but in so extensive a scheme as we propose it will be advisable for the promoters of the measure at once to establish a set of docks and warehouses of the most perfect description, as has been done in all the docks which have been constructed in and adjacent to london, and we have accordingly designed a set of such warehouses and yards as part of the plan.
“details of the plan.
“commencing at the river mersey, we propose to dredge out and widen wallasey creek at least to the depth of three feet under low water of spring tides, being four feet below the sill of prince’s145 dock, and this for 200 feet in width up as far as the entrance into the basins; to lay the sill of the greater entrance lock at that level, also the sill of the basin of the barge lock. the barge entrance lock to have a lift of ten feet; the ship lock four feet; so as to give the same water when the gates are opened as into the prince’s dock. the side of wallasey creek will be quayed for four hundred yards below the entrance of the dock, to facilitate transporting vessels into and out of the basins.
“the tide basin is 1000 yards long, and 100 yards wide in the middle, curving on the north side towards the locks at each end, the south side receding 100 feet, so as to give berthage to timber vessels, and in the front of them a sloping wharf and bonding yards for timber; a line of barge canal between these yards and the warehouses on the main dock will facilitate the removal of the timber without interfering with the shipping.
“the entrance lock into this basin from the tideway will be fifty feet wide, the entrance wing walls widening gradually to 100 feet, to afford easy access to the shipping when both gates are thrown open. at low water, neaps, or half tide, two or three vessels may pass at a time. the upper lock between this basin and the canal to be double; one large lock, forty-five feet wide and 160 feet long, for great ships, and another, twenty-five feet wide, for smaller vessels, with gates at each end, pointing both to land and seawards. these locks to rise to four feet below the old dock sill of liverpool, and thus to have twenty-two feet water in the canal on the level of an eighteen feet tide, which we propose to make the surface level of the canal.
“the ship dock parallel to this basin will be 400 yards long and 100 wide, with warehouses on each side, supported by iron pillars, so as to form a covered wharf, as at the st. katherine’s dock in london; behind these warehouses a parallel barge canal fit for river flats, forty feet wide, which will, as in holland, be found146 a singular convenience. these canals communicate with a dock and basin for flats only, whence the barges may be let down into the creek during the ebb; and as they navigate at the lowest water they will be ready to pass up the mersey with the first of the flood; and in like manner, coming down with the last of the ebb, will get into the pool and enter the dock without losing a tide. ships from the mersey, in like manner, may enter the basin with half-flood, and be ready to proceed down the swash with the first of the ebb.
“the flat marsh by the boilers yards is well adapted for this establishment, but as the ground beyond is high for some distance we propose the canal to be 124 feet only at water surface for 1000 yards from the locks, and to be lined with a stone wall on each side, so that this space will, in fact, be also a dock. afterwards the marsh widens, and here is a favourable place for another entrance basin and dock, if necessary. from this point we propose to continue the canal with sloping banks, the bottom to be four feet under the level of the old dock sill, and 163 feet in width at the surface of the water, which will be twenty-two feet in depth.
“the canal proceeds at first in the direction of the leasowe lighthouse, and approaches within half a mile of the shore, and about the same distance north of the village of moreton, and then turns to the westward, keeping half a mile inland from the villages of great and little meols through newton car, where it turns off to helbre island, and enters the strand about half a mile above the hotel; across the strand it is carried by embankments to the upper end of helbre island. a large breadth is allowed for the embankment on the sea-side, with facing mound of stone from the rocky point near the red stone to within 600 feet of the point of helbre. the head of this pier to be of rough stone, rounded off, and carefully paved. a pier head is to be built in helbre of 300 feet in length, leaving an opening of 300 feet into the tide harbour, which is fifty147 acres in extent, and to be cleared to at least low water of a spring-tide, and preserved of that depth by scouring.
“a quay wall is to be constructed of hewn stone along the helbre island from the pier-head 600 yards to the tide lock, which is to be fifty feet wide, as at wallasey; another tide lock of similar dimensions on the north side of the harbour. the north pier is only intended to be of rough stone; but a short covering pier will be made to protect that lock and facilitate the entry of ships. above these locks the canal is to be formed into a tide basin of 500 yards in length, the level of which may be kept at that of the tide of the day; and at the upper end are two parallel canal locks, as at wallasey, with gates pointing to the sea and land at each end, as the tide will occasionally rise higher than the level of the water in the canal.
“from helbre island to the middle helbre, thence to the eye, and from that to the shore at kirby church, an embankment and road will be carried along the ridge and made water-tight. by this and the canal a pond, as has already been described, will be enclosed, of 640 acres, which will fill at spring-tides to the depth of nine feet, containing 3,000,000 of cubic yards, and may be all emptied for the purpose of scouring the outer harbour; but at the latter part of the spring tides it will be advisable to fill this pond as a reservoir for lockage water, for which purpose it may be drawn down three feet to the canal level, and will hold 1200 locks-full for ship lockage at each end, and, if necessary, 1000 more locks-full may be drawn off without any material inconvenience to the navigation.
“we now subjoin an estimate of what we conceive will be the expense of completing these works, including an extensive range of warehouses on each side of the dock at wallasey pool, and of enclosed timber yards along the tide basin; and for all the items we have made a liberal provision.
148
“estimate.
excavations in wallasey creek and helbre harbour, also in the locks, basins, and canal to helbre, and barge canal and basins, ￡436,017
quay walls on creek, basins, locks, and canal at wallasey pool, 230,100
bridges and tunnels, 38,000
piers and quays walls, helbre harbour, 95,100
locks, dams, and culverts, helbre harbour, 111,000
warehouses at wallasey pool, inclosure walls, and paving, 183,000
purchase of land, 125,000
for surveys, act of parliament, law expenses, superintendents’, lock-keepers’, and other offices, etc., and contingencies on works, fifteen per cent., 182,731
￡1,400,948
“for the above sum a floating harbour will be obtained of seven miles in length, capable of indefinite enlargement, with extensive warehouse accommodation, and with a sea-port at either end on the two separate estuaries. that this is not too great for the wants of the country will be at once admitted by those who consider the vast extent of shipping usually moored in the thames, notwithstanding all its docks; the total inapplicability of the rivers mersey or dee to such a purpose; and the confined space which even the docks of liverpool can afford for the accommodation of a trade now hardly inferior to that of the metropolis, and certainly and rapidly increasing.
“thos. telford.
robt. stevenson.
alexander nimmo.
“london, 16th may 1828.”
“further report respecting the proposed two new ports, etc., on the rivers dee and mersey, adjacent to liverpool.
“in the foregoing report we have shown the form and expense of this establishment when completed upon an extensive and perfect plan. at the commencement, however, of so great an undertaking149 it is not to be expected that all the conveniences we have proposed can be immediately required; a considerable portion may therefore be deferred until the wants and increasing demands of trade shall show them to be necessary. in the meantime the essential parts of the improvement may be effected, with a smaller expenditure of capital, so as to obtain all that safety and facility of access which we have shown to be leading features of this plan.
“we have proposed to make the canal from wallasey to helbre wide enough for three great ships, so as to admit of part of it being used as a floating harbour, still leaving room for navigation; but for navigation alone it will be quite enough to adopt the dimensions of the caledonian canal, viz., 120 feet at surface, and if the trade should increase so as to require it, instead of widening it, a parallel canal may hereafter be made, with a bank and two towing-paths between, leaving the whole of the opposite banks applicable to berthage and commercial establishments. the same locks will serve at either end, and the transporting of ships be greatly facilitated; and the construction of this canal, or repair of the other, may be effected without any interruption to the navigation by such an arrangement. again, the double locks at the wallasey end of the canal, intended for the greater dispatch of business, may very well be deferred for the present, and the entrance basin made of smaller dimensions. the ship dock there may at first be made as a part of the canal, and quayed on one side only, and afterwards widened and completed when wanted. the half tide dock may be dispensed with by enlarging the barge tide dock so as to serve also for ships, and the quay walling of the pool and of the first mile of the canal may also be deferred. the warehouses at wallasey dock may be dispensed with at first, or left to individual capital; but it will be highly proper to secure a sufficient quantity of land to enable all these improvements to be undertaken at some future period. we do not deem it advisable to give up the enlargement and deepening of the entrance of wallasey pool, as on that depends much of the150 utility of the plan in giving access to vessels at low tides; and for a similar reason we would preserve all the works proposed for the harbour at helbre island. upon this modified plan the expense, as below, will be ￡734,163.
“thos. telford.
robt. stevenson.
alex. nimmo.
“chester, july 14, 1828.
“estimate.
excavating tide basin, barge dock, and half of ship dock, at wallasey end, ￡25,000
walling along the pool, from brassey’s works, also the barge dock and one side of ship dock, 31,500
ship lock, barge lock, and tide gates for basin, and two swivel bridges, 36,500
dredging wallasey creek, as before, 20,000
land and damages, 51,000
￡164,000
fifteen per cent. contingencies, 24,485
for wallasey end, ￡188,485
excavating canal, ￡207,403
bridges and tunnel, 22,000
land and damages, 27,000
￡256,403
fifteen per cent., 38,460
for the canal, ￡294,863
pier and quay walls from helbre, as before, ￡95,100
locks, dams, and culverts, do., 111,000
excavation in harbour, 10,000
strand and damages on isle, 2,000
fifteen per cent., 32,715
￡250,815
general total, ￡734,163 ”
151 i have given the reports of the three engineers to whom this question was remitted, to show the very comprehensive view they took of the important subject referred for their opinion; and it is almost unnecessary to tell professional readers that after a lapse of nearly a quarter of a century the embryo but comprehensive proposal of telford, stevenson, and nimmo resulted in the modified but still large birkenhead dock scheme of j. m. rendel.
* * * * *
the original design for the improvement of the tay was made by messrs. robert and alan stevenson, in 1833, and in connection with my father’s life a short account of the works may be desirable as illustrating his practice in river engineering in the tay and other rivers.
the river tay, with its numerous tributaries, receives the drainage water of a district of scotland amounting to 2283 square miles, as measured on arrowsmith’s map. its mean discharge has been ascertained to be 274,000 cubic feet, or 7645 tons of water per minute. it is navigable as far as perth, which is twenty-two miles from dundee and thirty-two from the german ocean.
before the commencement of the works, certain ridges, called “fords,” stretched across the bed of the river, at different points between perth and newburgh, and obstructed the passage to such a degree that vessels drawing from ten to eleven feet could not, during the highest tides, make their way up to perth without great difficulty. the depth of water on these fords varied from152 one foot nine inches to two feet six inches at low, and eleven feet nine inches to fourteen feet at high water of spring tides; so that the regulating navigable depth, under the most favourable circumstances, could not be reckoned at more than eleven feet. the chief disadvantage experienced by vessels in the unimproved state of the river was the risk of their being detained by grounding, or being otherwise obstructed at these defective places, so as to lose the tide at perth,—a misfortune which, at times when the tides were falling from springs to neaps, often led to the necessity either of lightening the vessel, or of detaining her till the succeeding springs afforded sufficient depth for passing the fords. the great object aimed at, therefore, was to remove every cause of detention, and facilitate the propagation of the tidal wave in the upper part of the river, so that inward-bound vessels might take the first of the flood to enable them to reach perth in one tide. nor was it, indeed, less important to remove every obstacle that might prevent outward-bound vessels from reaching newburgh, and the more open and deep parts of the navigation before low water of the tide with which they left perth.
the works undertaken by the harbour commissioners of perth for the purpose of remedying the evils alluded to, and which extended over six working seasons, may be briefly described as follows:—
1st, the fords, and many intermediate shallows, were deepened by steam dredging; and the system of harrowing was employed in some of the softer banks in the lower part of the river. many large detached boulders and “fishing cairns,” which obstructed the passage of vessels, were also removed.
153 2d, three subsidiary channels, or offshoots from the main stream, at sleepless, darry, and balhepburn islands, were shut up by embankments formed of the produce of the dredging, so as to confine the whole of the water to the navigable channel, and the banks of the navigable channel were widened to receive the additional quantity of water which they had to discharge.
3d, in some places the banks on either side of the river beyond low water mark, where much contracted, were excavated, in order to equalise the currents, by allowing sufficient space for the free passage of the water; and this was more especially done on the shores opposite sleepless and darry islands, where the shutting up of the secondary channels rendered it more necessary.
the benefit to the navigation in consequence of the completion of these works was of a twofold kind; for not only was the depth of water materially increased by actual deepening of the waterway, and the removal of numerous obstructions from the bed of the river, but a clearer and a freer passage was made for the flow of the tide, which begins to rise at perth much sooner than before; and as the time of high water is unaltered, the advantages of increased depth due to the presence of the tide is proportionally increased throughout the whole range of the navigation; or, in other words, the duration of tidal influence has been prolonged.
the depths at the shallowest places were pretty nearly equalised, being five feet at low and fifteen feet at high water, of ordinary spring tides, instead, as formerly, of one foot nine inches at low and eleven feet at high154 water. steamers of small draught of water can now therefore ply at low water, and vessels drawing fourteen feet can now come up to perth in one tide with ease and safety.