264 
ZAHM. 
resistance increases with the length up to infinity. To illus¬ 
trate these features, let the equation for the total resistance 
be applied to the data of an experiment. 
For practical engineering purposes, which need not be 
detailed here, it was found desirable to measure the total 
resistance of a number of wedge forms such as shown in 
figure 6. The models are all 1 inch thick and of the widths 
given in the second column of table V. The size of the 
models is given in the first column as so many calibers, 
their outlines being circular arcs whose radii are an even 
number of times the thickness of the wedge. The actual 
measured values of the resistance per unit length of post at 
10 feet a second are given in the last column of the accom¬ 
panying table and shown diagrammatically in figure 7 by 
the little circles. 
Table V. 
Computed and Observed Resistances of Duangular Cylinders One Inch Thick, 
One Foot Long, and of Various Widths. 
Caliber of 
model. 
Width of 
model. 
Computed resistance. 
Observed 
resistance. 
Head. 
Frictional. 
Total. 
1 
1.76 
0.00687 
0.000212 
0.00708 
0.00702 
5 
4.41 
0.00307 
0.000511 
0.00358 
0.00375 
10 
6.20 
0.00221 
0.000687 
0.00290 
0.00298 
20 
8.88 
0.00155 
0.000960 
0.00251 
0.00267 
30 
11.05 
0.00125 
0.001178 
0.00243 
0.00250 
40 
12.77 
0.00108 
0.001348 
0.00243 
0.00238 
50 
14.31 
0.000968 
0 001500 
0.00247 
0.00235 
60 
16.00 
0.000870 
0.001664 
0.00253 
0 00253 
70 
16.87 
0.000822 
0 001746 
0.00257 
0.00253 
80 
18.25 
0.000772 
0.001884 
0.00266 
0.00261 
100 
20.12 
0.000690 
0.002061 
0.00275 
0.00285 
150 
24.87 
0.000557 
0.002505 
0.00306 
0.00299 
Now let us apply to these data the equation 
E = c sin a + 2 fx. 
Taking c = 0.0139 pounds, the normal resistance of the 
major section at 10 feet a second, as computed by Langley’s 
