INVENTIONS AND WARFARE 165 
the old building was repaired with this apparatus. 
The Field Museum never used the cement gun any 
more but some friends came along and offered to 
put money enough behind the idea to perfect, manu- 
facture, and sell it. As with all such things the first 
money went and then a second like amount, but in 
the end the cement gun succeeded, and during the 
war it, among other things, was used to make the con- 
crete ships. This occupied most of my time between 
1907 and 190g. In fact, I drove the first motorized 
cement gun down to the house of its chief financial 
backer on Long Island in 1909, and went back to 
New York to go again to Africa. 
As I am no longer financially interested in the ce- 
ment gun, I may say with pride that there are now 
approximately 1,250 machines in use, not only in the 
United States, but also in the principal foreign coun- 
tries. In addition to the use for which it was origi- 
nally designed, that of restoring masonry and con- 
crete structures, many other important purposes are 
now served by this mechanism. In coal mines it is 
being used to keep slate roofs from falling and to 
fireproof the timbers. Irrigation ditches and reser- 
voirs are being lined and dams are being faced and 
protected against the destructive action of water 
and frost by this method. In tunnel construction, 
a lining put in with the cement gun prevents falls 
and insures an absolute sealing. It protects steel, 
protects piles against teredo and fire, protects struc- 
tures against acid, restores boiler settings and pre- 
serves them from further action of the heat, rebuilds 
