meanwhile no time was lost in getting to the root of the mischief.

the danger could not be averted by switching off the power altogether at the various electrical stations of the metropolis. at intervals along the tubes were immense accumulators which for the present could not be touched. it was these accumulators that rendered the streets such a ghastly peril.

it was the electrical expert to the county council—alton rossiter—who first got on the track of the disaster. more than once before, the contact between gas and electricity had produced minor troubles of this kind. gas that had escaped into man-holes and drains had been fired from the sparks caused by a short-circuit current wire. for some time, even as far back as 1895, instances of this kind had been recorded.

but how could the gas have leaked into the tube, seeing that it was a steel core with a solid bedding of concrete beyond? unless an accident had happened when the tube was under repair, this seemed impossible.

the manager of the associated tubes was quite ready to afford every information to mr. rossiter. the core had corroded in bond street in consequence of a settling of the earth caused by a leaky water-main. the night before, this had been located and the steel skin stripped off for the necessary repairs.

mr. alton rossiter cut the speaker short.

"will you come to bond street with me, mr. fergusson?" he said; "we may be able to get into the tunnel there."

fergusson was quite ready. the damage in bond street was not so great, though the lift shaft was filled with débris, and it became necessary to cut a way into the station before the funnel was reached.

for a couple of hundred yards the tube was intact; beyond that point the fumes of gas were overpowering. a long strip of steel hung from the roof. just where it was, a round, clean hole in the roadway rendered it possible to work and breathe there in spite of the gas fumes.

"we shall have to manage as best we can," rossiter muttered. "for a little time, at any rate, the gas of london must be cut off entirely. with broken mains all over the place the supply is positively dangerous. look here."

he pointed to the spot where the gas main had trended down and where a short-circuit wire had fused it. here was the whole secret in a nutshell. a roaring gas main had poured a dense volume into the tube for hours; mixed with the air it had become one of the most powerful and deadly of explosives.

"what time does your first train start?" rossiter asked.

"for the early markets, four o'clock," fergusson replied. "in other words, we switch on the current from the accumulator stations at twenty minutes to four."

"and this is one of your generating stations?"

"yes. of course i see exactly what you are driving at. practically the whole circuit of tubes was more or less charged with a fearful admixture of gas and air. as soon as the current was switched on a spark exploded the charge. i fear, i very much fear, that you are right. if we can only find the man in charge here! but that would be nothing else than a miracle."

all the same the operator in charge of the switches was close by. fortunately for him the play of the current in the tube had carried the gases towards st. james's street. the explosion had lifted him out of his box, and for a time he lay stunned. dazed and confused, he had climbed to the street and staggered into the shop of a chemist who was just closing the door upon a customer who had rung him up for a prescription.

but he could say very little. there had been an explosion directly he pulled down the first of the switches, and his memory was a blank after that.

anyway, the cause of the disaster was found. to prevent further catastrophe notice was immediately given to the various gas companies to cut off the supplies at once. in a little time the whole disastrous length of the tube was free from that danger.

by the afternoon a committee had gone over the whole route. at the first blush it looked as if london had been half ruined. it was impossible yet to estimate the full extent of the damage. in st. james's street alone the loss was pretty certain to run into millions.

down in whitehall and parliament street, and by westminster bridge, the damage was terrible. here sharp curves and angles had checked the rush of expanding air with the most dire results. huge holes and ruts had been made in the earth, and houses had come down bodily.

most of the people out in the streets by this time were properly equipped in indiarubber shoes and gloves. it touched the imagination strongly to know that between a man and hideous death was a thin sheet of rubber no thicker than a shilling. it was like walking over the crust of a slumbering volcano; like skating at top speed over very thin ice.

towards the evening a thrilling whisper ran round. from deptford two early specials had started to convey an annual excursion of five hundred men and their wives to paddington, whence they were going to windsor. it seemed impossible, incredible, that these could have been overlooked; but by five o'clock the dreadful truth was established. those two specials had started; but what oblivion they had found—how lingering, swift, or merciful, nobody could tell.