301 Royal Society : — 



Feb. 27. — Lieut. -General Sabine, President, in the Chair. 



The following communication was read : — 



"On the Resistance of the Air to Rifled Projectiles." By J. A. 

 Longridge, C.E. 



The introduction of elongated rifled projectiles having rendered it 

 necessary to reconsider the laws of resistance which had been deduced 

 by Robins, Hutton, and more recent authors, such an investigation 

 is the object of this paper. 



It is first shown that Hutton' s law, 

 ~R=av-t-bv 2 , 



if applied to the results obtained by the Special Armstrong and Whit- 

 worth Committee, 1866, leads to the following equation, 



,= 1620 log /X=™I^"1, 



where Y is the initial velocity, 



v the residual velocity at the distance x from the gun. 

 In like manner it is shown that the law adopted by Piobert, 



R=A0 2 +B*; 3 , 

 leads to the equation 



oin<-l fV— 994 vl 



and the law 



R=Av 3 + Bw 4 



to the equation 



ofttQi TV 2 - 958850 v 2 l 



These equations all fail by x becoming infinite when # = 1015, 994, 

 and 979 respectively. 



It is, however, observed that, in the assumption of the law of the 

 resistance, the higher the power of velocity the longer does the cor- 

 responding equation give rational results ; and by assuming R=aw p 

 with the same data, the following equation was obtained, 



which gives consistent results for all values of v. 



The value of p here is 8*747, which would give the resistance 

 varying nearly as the ninth power of the velocity. 



This result led the author of the paper to doubt the accuracy 

 of the experiments, and to seek for further and more correct data, 

 which were obtained from a minute (No. 23,351) of the Ordnance 

 Select Committee, dated 21st September 1867, containing the results 

 of experiments showing the loss of velocity of two projectiles, one 

 of 8*818 lbs., and the other of 251 lbs., in passing through certain 

 given distances with given initial velocities, varying from about 1500 

 feet to 600 feet per second. 



From these results a diagram was constructed, and for each pro- 



