648 
Proceedings of the Royal Society 
horizontal projection of the ball's path, that path being a line of 
double curvature. 
As an example of the variety and completeness of the information 
conveyed by such tables, we may cite the path detailed in the pre- 
ceding table and represented by fig. 3. 
The ball is projected from A with the velocity of 2T8, and at 
once encounters a resistance 4§ times greater than its weight. Ths 
speed is rapidly lessened, and the path is deflected to become hori- 
zontal at Y, where, in the present instance, the resistance is just 
equal to the weight. On account of this resistance the speed is 
still slackened, but gravity now comes to accelerate the motion 
downwards, and, at about the fifth interval from V, has overcome 
the retardation, thereafter the velocity slowly increases, and tends 
ultimately to reach the limit l'OO. 
Those cases in which the characteristic angle A of fig. 4 is 
obtuse have little or no application to gunnery ; in them the path 
is never horizontal, but is inclined downwards all along. 
The analysis of these motions is complex, and the calculations 
thereon following are tedious, but the results, when tabulated, are 
of easy application. The theory would be uninteresting to those 
engaged in the actual business, just as the mode of construction of 
trigonometric and logarithmic tables is scarcely ever thought of by 
the navigator or surveyor. What we have at present to consider is 
the advantage to be gained by the compilation of a series of tables 
such as those sketched out. 
3. On some Physical Experiments relating to the Function of 
the Kidney. By David Kewman, Glasgow. Communi- 
cated by Professor M'Kendrick. 
[Abstract.) 
This paper treats of the physical influences which promote the 
secretion of urine, as far as can be demonstrated by experiments 
upon animal membranes and the kidneys of animals recently killed. 
Before going on to consider the subject I may be permitted simply 
to mention the theory held regarding the means by which the 
