4'04< THIRD REPORT — 1833. 



II. Remarks on the Results of the Experiments. — The pre- 

 ceding table of results appears sufficient, when combined with 

 some other data which I have obtained, to authorize some in- 

 teresting inductions concerning the law and the cause of the 

 remarkable inequality of the quantities of rain at different ele- 

 vations above the ground. 



1. The notion which is most generally entertained of the 

 cause of this inequality is, that wind, blowing horizontally, 

 causes fewer drops of rain to fall upon the more elevated 

 gauges. That this notion is a mere fallacy, the least acquaint- 

 ance with mechanics is sufficient to prove ; for certainly the 

 number of drops of rain which fall, imder the joint influence 

 of gravitation and ordinary wind, upon horizontal surfaces, 

 will be, ccBteris paribus, exactly the same at all elevations be- 

 low the point from which the rain descends. 



2. It is supposed by some that eddy winds, produced by 

 the sides of buildings and rising upwards, may deflect the rain 

 so as to prevent much of it from falling on those buildings. It 

 is certainly conceivable that this irregular action against gra- 

 vity may, when very violent, under particular circumstances, 

 produce a sensible effect, and such appears to be recognised 

 by our experiments, in one instance, during the equinoctial 

 period of March 1832. 



But it is evident that in the majority of cases the effect of 

 the eddying wind is quite unimportant. I have noticed in se- 

 veral instances the fact, that the wind which accompanies the 

 fall of rain takes the line of the rain-drops themselves ; and 

 on the Minster, in particular, this was very strikingly illus- 

 trated, when, with my friends Mr. Jonathan Gray and Mr. 

 William Gray, junior, I watched the progress of a storm for 30 

 miles down the vale of York. The wind was insensible except 

 during the fall of rain, and then it came downward with the 

 drops. There is no need of further remarks on this subject, 

 because the results recorded are too regular, considerable, and 

 consistent with known properties of the atmosphere, to be 

 explained by such fluctuating and inadequate agency. 



3. With respect to the observations on the ground, I have 

 procured several registers of the rain which fell in and about 

 York, for comparison with the observations in the Museum 

 garden. By this comparison it is abundantly evident that the 

 situation of the gauge, its exposure to eddy winds, and other 

 irregularities, have very little influence upon the mean results. 

 Wliile the gauge in the Museum garden is remarkably open on 

 all sides, and set level with the ground, Mr. J. Gray's is raised 

 thi'ee feet above, and placed in a small garden, surrounded by 



