220 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
steel, like nickel steel. It is smelted in open-hearth furnaces, the 
charge for which consists of pig iron and selected scrap. Over 
21,000 workmen were employed in big-gun construction and as many 
more in the fabrication of gun carriages and fire-control instruments. 
Each carriage, moreover, in the case of mobile guns, required a shield 
of armor plate. In 1918 w^e produced over 8,400 cannon forgings. 
As regards the effective weight of the guns themselves, it is significant 
that the 800-pound gun of nickel steel of 1918 fires as heavy a projec- 
tile as the 1,650-pound bronze gun of the Napoleonic wars. 
Each gun required an immense amount of heavy equipment, 
mostly, of course, of steel in the form of limbers, caissons, auto trucks 
and tractors, caterpillar mounts, and other devices. Each 155- 
millimeter howitzer involved some 200 items of miscellaneous equip- 
ment, as air and liquid pumps and tools. All this required the erec- 
tion of great base repair shops — in themselves larger than some pro- 
ducing arsenals. 
The extraordinary development of barrage fire by which the war 
was characterized was conditioned on the use of thousands of deli- 
cate and accurate sighting instruments and involved the expenditure 
of ammunition in quantities hitherto unknown. The Union Army 
at Gettysburg fired 32,781 rounds. The United States fired at St. 
Mihiel over 1,000,000 rounds and the British at the Somme 4,000,000 
rounds. In the Civil War Union artillerists fired 4 rounds per gun 
per day, whereas from January 1 to November 11, 1918, the average 
for American guns was 30, for French 34, and for British 35 rounds 
per day. 
As to shell production, we turned out prior to the armistice, and 
in the 75-millimeter size alone, about 4^ million high-explosive 
shells, one-half million gas shells, and over 7^ million shrapnel. 
The various sorts of grenades made, of course, wholly different 
demands upon raw materials for their construction. The defensive 
or fragmentation type was made of malleable iron; the offensive 
grenade had a paper shell, its purpose being to kill by the concussion 
of the charge; gas and phosphorus grenades were formed of sheet 
metal and the thermite shell of teme-plate. And there were also 
incendiary and rifle grenades. About 28,000,000 of all kinds were 
produced by November, 1918, but only a small proportion— less, 
indeed, than 4 per cent — were loaded. Contracts had been placed for 
68,000,000 of the defensive type alone. 
At the time of the armistice the standard equipment of a division 
called for 260 heavy machine guns and 768 light automatic rifles, 
and the total of automatic arms made on army orders alone in the 
United States and Canada was over a quarter of a million. About 
32,000 Lewis aircraft guns were completed. It was found neces- 
