1904.] Air Resistance to Projectiles at High Velocities. 267 



3. The majority of the chromium enhanced lines occur in the 

 solar spectrum, though some appear to be missing. 



4. Some of the Fraunhoferic lines correspond to metallic lines special 

 to the spark spectrum, and lacking in the arc, and probably for this 

 reason they were left unorigined by Rowland. 



" Air Resistance Encountered by Projectiles at Velocities up to 

 4500 Feet per Second." By A. MALLOCK, F.R.S. Received 

 November 3, Read November 17, 1904. 



The work done by Prof. Bashforth on the subject of air resistance is so 

 well known that I need hardly refer to it except to say that his results 

 have, with minor alterations, been confirmed by subsequent experi- 

 menters. The greater part of Professor Bashforth's work related to 

 velocities under 2500 feet per second, and the object of the present 

 experiments was to examine the co-efficient of air resistance at higher 

 speeds. 



In the years 1895-97, Major the Hon. T. F. Fremantle and 

 Colonel H. Mellish made a series of experiments on the remaining 

 velocities of the service *303 bullet by shooting into a ballistic pendulum 

 from ranges varying from 12 up to 1000 yards. These experiments 

 were made with great care, each bullet and charge being separately 

 weighed, and from the results which they communicated to me I 

 computed the co-efficient of resistance for velocities ranging from 

 2100 f.s. to 900 f.s. I suggested then that with light bullets we 

 could probably extend the ballistic tables very considerably, using the 

 pendulum to measure the velocity, and shortly after this we made 

 some trials with various aluminium bullets. We found, however, that 

 with cordite of the size used for the service charge of the *303 rifle a 

 great part of the explosive was blown out unburnt when the light 

 bullets were used. It was evident, therefore, that in order to get the 

 velocities we required, a much finer cordite than the No. 3 of the service 

 charge would have to be used. We found also that a considerable 

 deposit of aluminium was left in the barrel after firing. 



From various causes I have not been able to proceed with the 

 experiments until the present year, when having obtained some cordite 

 of diameter '01 inch, I again tried aluminium bullets, but the metallic 

 fouling proved fatal to accurate and consistent results. I then tried 

 shooting with lignum vitae plugs which did very well up to velocities of 

 about 2500 f.s., but at this velocity, sometimes, and generally at 

 higher velocities, the plugs broke up under the action of centrifugal 

 force. I again, therefore, reverted to aluminium, but on the bullets 

 I made two small cannelures, fig. 1, which were filled with a composi- 



VOL. LXXIV. T 



