1820.] on Rain-Gavges. 42;j 



taught us that equal causes produce equal effects. A rain- 

 gauge, therefore, which would just receive the 1000 drops at the 

 height we at first supposed them, would exactly receive them at 

 the earth's surface, let their general inclination at any time be 

 what it may. 



Mr. Boase himself seems to be the very first person who 



would like to prove " that equal forces acting on equal dropss 



produce unequal effects ;" for he tells us that " the wind disj)erses 



the rain over a greater surface ; " that is, it carries one drop muck 



further than it does another — a pretty specimen of equal effect! ! I 



In order the more effectually to delude himself, Mr. Boase 

 very prudently takes care not to trace all his drops from the saine 

 height, nor to make them all describe ecjual curves similarly 

 situated ivith respect to the horizon.* Is it not distressing to see 

 him go through so many numerical computations, while the prin- 

 ciples on which they are founded have no existence but in his 

 own imagination ? In short, throughout the whole he seems to 

 enjoy much of that perfect confidence and composure which 

 usually characterize a well-established delusion. 



After what I had formerly advanced on this subject, I should, 

 not have considered your correspondent's paper deserving of any 

 reply whatever, were it not that I find there are many still 

 labouring under the same hapless mistake. 



With the view of guarding against any misconstruction, I beg 

 to remark that it was never my object, though Mr. B. seems to 

 think so in his /rVs^ article, to disprove the well-known fact of a 

 rain-gauge collecting less water in a more exposed situation. 

 On the contrary, I have admitted that in my former papers ; but 

 my object was to prove, as I have so often done, that the general 

 inclination of the rain, in which my learned opponents rest their 

 explanation, does not in the least affect the phenomenon ia 

 question ; and that, therefore, we must seek for an explanation 

 in something else ; probably, as I said before, in the obstructioa 

 which the gauge itself oft'ers to the wind. I am, Sir, 



Your most obedient servant, 



Henry Meikle, 



♦ The following simple facts are obvious to every one who has the least acquaint- 

 ance with curves; and are well worth tlie attention of your coi respondent : 



If two curves, which are every way equal, and similarly situated on parallel 

 planes, have two parallel straight lines for their axes, then all straight lines joining 

 the corresponding points of the.-e curves are equal to one another. 



Now in the curves described by the rain-drops, the horizontal distance is always 

 the distance of two corresponding^; points. 



It is not poi-sible for two equal curves similarly situated in the same plane to be 

 every where equidistant ; or to have their perpendicular distance every where the 

 came. Straight lines only have this property. 



