348 



Mr. J. Prescott on the 



to veer bodily to the right, giving the deviation known as 

 Drift. In the following investigation this drift, as well as 

 the deviation due to a side wind, will be determined as far 

 as possible. The effect of the wind is already known, and is 

 given in Professor Greenhiirs ' Notes on Dynamics/ but the 

 theory of drift does not seem to be well known, for Professor 

 GreenhilPs proposed formula for it, for which, however, he 

 claims no theoretical basis, differs very considerably from 

 the result arrived at in this paper. Since the drift is cal- 

 culated in this paper from the same differentia] equations as 

 the wind effect, and our formula for the latter is known to 

 be correct, this should give confidence in the calculated 

 drift. 



33. In fig. 4, OApg is the vertical plane containing the 



Fig. 4. 



axis of the gun, OA being the direction of departure of 

 the shot. The figure is drawn in this position because the 

 geometry seems more intelligible than it does in its true 

 position. O is the centre of mass of the shot, E the point 

 where the line of resistance meets the axis. Og is the 

 direction in which would be moving at the instant we are 



