178 Mr. Boase on Rain-Ganges. [Sept. 



•7854 = 39*2700 ; so that the basin D would receive twice as 

 much water as the basin C, and the sloping would be twofold 

 heavier than the verticfil fall of the same rain. 



Thirdly, Because a continued increase of the horizontal velo- 

 city would at last compress the supposed column into a dense 

 sheet of water no further compressible ; but the principle assumed 

 requires that the compression should still proceed, which is 

 impossible. 



Thus, I conceive, Mr. Meikle's position falls, without drawing 

 after it " so)ne of the simplest truths of geometry," because those 

 truths were inapplicable to the question. 



Others of the simplest truths assure me that whatever composi- 

 tion of forces affects one drop of the assumed column of rain 

 equally affects every other drop ; and consequently whatever 

 their perpendicular distance was, such it will be so long as the 

 same cause exists. 



For let A B C be supposed a so/id column, or cylinder ; and 

 let it be inclined to the same angle, as before shown, of 30° as 

 B E, it is obvious that its perpendicular diameter a b remains 

 unaltered, but its horizontal section a f b e is twice as great as 

 its perpendicular section, or the area ot the basin a db c, which, 



as before shown, is = 78-5400, whereas the ellipsis is 20 x 10 

 X -7854= 157"0800.'*' Hence it appears, that "the distance 

 of the points in which the drops pass through a horizontal plane" 

 does vary in proportion to the sine of inclination, unless it can be 

 proved, in reference to the descending rain, that equal forces 

 acting on equal drops produce unequal effects. Surely your 

 respectable correspondent was rather too much inclined to sar- 

 casm when, after remarking that " admitting the opinion of these 

 learned gentlemen to be correct, the quantity of rain which falls on 

 am/ given space of ground during wind would be less than what 

 came awatj from the area of the cloud," he adds : " Query, Is the 

 rest annihilated, or ivhat becomes of it that it does not reach the 

 earth ? " The answer is plain, it does reach the earth, but is 

 dispersed over a greater surface. The shower which falhng ver- 

 tically would have covered (suppose) 10 squareleagues, if carried 

 by a horizontal velocity equal to the mean downward velocity to 

 an angle of 45° will be dispersed over 13^ leagues, if, by a hori- 

 zontal velocity as 2 to 1, at the angle of 30° over 20 leagues, and 

 if by a force as 4 to 1, at the angle of 15°, over 40 leagues, and 

 so on. If this hypothesis be true, it will, I think, afford a satis- 

 factory solution of the phenomenon of raiu-guages at different 

 heights indicating a different fall of rain. 



If I have succeeded in proving that the perpendicular distance 

 of the drops composing a given column of rain is not varied by 



*■ It may be fight to remark that the paths of the drops falling obliquely will 

 not be straight, but parabolic lines. This will vary the angle in a small degree, 

 but does notaftcct t!ic principle. 



