8 Trans. Acad. Sct. of St. Louis. 
8. NUMERICAL APPLICATIONS OF ForMuLA [VIII]. 
w= (y + a5) ala + a5) 
P means the resistance of still air to the motion of an air- 
ship, moving V miles per hour, determined by experiment or 
calculated by means of formula [IXj. 
Pp V r feet A sq. ft. H’ 
100 10 10 314.16 5.08 
100 15 5) 78 . 54 9.8 
650 15 8.1 206 .— 85.5 
400 20 10 314.16 44.51 
900 30 10 314.16 150.5 
1000 60 20 1256. 64 206 .— 
The above six cases apply to six different air-ships. The 
third is approximately that of Mr. Wellman, judging from the 
data he has published. 
9. In the discussions of this paper, I have made no attempt 
to approximate the loss of energy due to friction in the mechan- 
ism, or to the friction of the air upon the blades; or that due to 
defective design; or to the impact of the propeller current upon 
the frame-work, its contents and connections. 
Neither have I allowed for the energy spent fruitlessly upon 
diverging currents of air. To prevent, or rather to utilize such 
currents, I propose a short and thin enclosing cylinder for each 
propeller, with a slightly-flaring forward end. 
I am preparing to experiment upon ‘‘lifting” fans (with vertical 
shafts) of various radii and various numbers of blades, and with 
enclosing cylinders of various lengths.* 
* T learn from my friend, Dr. Octave Chanute, that experiments with 
enclosing cylinders have been made in Europe, but I have no access to their 
results. 
