otton and got up an engine with an arrangement whereby I
could feed this gun-cotton strip into the cylinder and explode it inside
electrically. The feed took place between two copper rolls. The copper
kept the temperature down, so that it could only explode up to the point
where it was in contact with the feed rolls. It worked pretty well;
but once the feed roll didn't save it, and the flame went through and
exploded the whole roll and kicked up such a bad explosion I abandoned
it. But the idea might be made to work."

Turning from the air to the earth, it is interesting to note that the
introduction of the underground Edison system in New York made an appeal
to inventive ingenuity and that one of the difficulties was met as
follows: "When we first put the Pearl Street station in operation, in
New York, we had cast-iron junction-boxes at the intersections of all
the streets. One night, or about two o'clock in the morning, a policeman
came in and said that something had exploded at the corner of William
and Nassau streets. I happened to be in the station, and went out to see
what it was. I found that the cover of the manhole, weighing about 200
pounds, had entirely disappeared, but everything inside was intact. It
had even stripped some of the threads of the bolts, and we could never
find that cover. I concluded it was either leakage of gas into the
manhole, or else the acid used in pickling the casting had given off
hydrogen, and air had leaked in, making an explosive mixture. As this
was a pretty serious problem, and as we had a good many of the manholes,
it worried me very much for fear that it would be repeated and the
company might have to pay a lot of damages, especially in districts
like that around William and Nassau, where there are a good many people
about. If an explosion took place in the daytime it might lift a few of
them up. However, I got around the difficulty by putting a little bottle
of chloroform in each box, corked up, with a slight hole in the cork.
The chloroform being volatile and very heavy, settled in the box and
displaced all the air. I have never heard of an explosion in a manhole
where this chloroform had been used. Carbon tetrachloride, now made
electrically at Niagara Falls, is very cheap and would be ideal for the
purpose."

Edison has never paid much attention to warfare, and has in general
disdained to develop inventions for the destruction of life and
property. Some years ago, however,