Discussion of Industries 137 
avoid all defects and to have the grain and density at each end 
the same. In some plants each lamination is weighed, matched, 
and balanced against the others, and by this means it is pos- 
sible to make the blades of the same propeller uniform as to 
weight, grain, texture, and yielding of the wood under stresses. 
At the high speeds used, the matter of accurate balance is 
essential to prevent racking vibrations. The laminations are 
glued up in a certain temperature and dried for a certain 
period. By means of a rotary cutter with a guide following a 
form whose outlines are exactly the same as the screw, the 
curved surfaces are formed much in the same way as gunstocks, 
The screw now goes from the outline machine to the duplicator, 
which turns out the screw with a shape very nearly as desired. 
The screw is again dried, surfaced, balanced, sanded, and 
inspected in detail, and is then ready for finishing, which is 
a careful, detailed series of applications and inspections. 
Spruce and ash as reported in 1912 hold the same relative 
place today; the other woods listed were introduced since the 
previous study. The average price paid in 1912 was $30.83 
while in 1919 it is $230.34. This is the greatest increase in 
cost seen in any industry, and is the highest average paid by 
any industry listed. 
TABLE 39 
ATRPLANES 
Quantity UsEp 
ANNUALLY Average 
dat Total cost Grown in |Grown out of 
Kinp oF Woop er 1,000 f. o. b. New York. | New York. 
sg factory | (Feet b. m.) | (Feet b. m.) 
Motaltaaat< seer 1,427,000 |} 100.00 |$230 34 $328,693 105,000 1,322,000 
Sitka spruce........ 1,066 ,000 74.70 |$250 00 $266 500) |oiac ca asmiae 1,066 ,000 
IASI otrte cre tie eae hobs 109 ,000 7.64 | 148 81 16,220 105,000 4,000 
Mahogany........- 100,000 7.01 | 250 00 20 OU0L erates auc 100 ,000 
White pine......... 74,000 5.19 | 140 00 LOSS Peers setae 74 ,000 
Western white pine. . 50,000 3.50 | 150 00 GOOD ava tortaiiaeee 50,000 
Wonglas arsed ss =. 20,000 1.40 | 95 00 LS 900M eveckes lie 20,000 
IBABSWOOG.-scrac se. 5,000 .35 | 150 10 CDI “|p eae seh 5,000 
Port Orford cedar... 3,000 .21 | 154 00 ABD eats eee ea 3,000 
