1835.] Miscellaneous. 61 



markable regularity of the progress of monthly temperature at York, and some 

 obvious relations between the quantity of rain collected, and the mean tempera- 

 ture of the period, some inferences unavoidably suggested themselves. 



First. The diminution at the upper stations is greatest in the cold, and least 

 in the warm seasons, and therefore the co-efficient is in some way inversely depend- 

 ent on tbe temperature. Mr. Phillips found the relation very nearly represent- 



t t 2 



ed by the formula 2 m = a _- ■+• a ,— where a = the ascertained value of m 



V t' 2 



for the whole year, t the mean temperature of ditto, and t f that of the particular 

 period. 



Secondly. The relation between the values of m and the dryness of the air is 

 inverse, whether expressed by the difference between the mean temperature and 

 the dew point, or, as that is seldom knowp, by the mean range of daily tempera- 

 ture, which had been determined for York from a long series of observations by 

 Mr. F. Cholmeley, to be as follows : 



January range, . . 8'0 May,., 19*7 September, 16*0 



February—, 10'1 June, 20-1 October 11-8 



March—, 13'1 July, 19*6 November, 9-0 



April — , 16*2 August, 17*7 December, 7'7 



General mean daily range, 14*08 

 Now if m be taken inversely as the mean range of temperature, r, or m = a 



•the accordance between the calculated and observed values of the co-ef- 

 r 



ficient is very close: 



(a = 2*29.) value of m. value of m. 



for the 7 coldest mouths, by calculation, 2 - 98 by observation, 2*8S 



7 warmest months, 1 '86 ]*97 



5 coldest months, 3*36 3'06 



5 warmest months, T73 1*73 



and so on throughout. The concluding remarks of Mr. Phillip's explain the 

 hypothesis he has framed for the explanation of the phenomenon which led to 

 the experiments, and to us it appears most clear and conclusive. 



•' So remarkable and continued an accoi dance between the co-efficients fixed 

 by observation and those derived by two methods from a very simple view of the 

 condition of the air as to heat and moisture, appears to me decisive of the ques- 

 tion as to the general cause of the variation of the quantity of diminution of 

 rain at any one height above the ground. It has already been shown how strictly 

 the observations warrant the conclusion that the ratio of diminution at different 

 heights is constant through the whole year. It is therefore rather as a matter of 

 very probable inference than a plausible speculation that I offer the hypothesis, 

 that the whole difference in the quantity of rain, at different heights above the sur- 

 face of the neighbouring ground, is caused by the continual augmentation of each 

 drop of rain from the commencement to the end of its descent, as it traverses 

 successively the humid strata of air at a temperature so much lower than that of 

 the surrounding medium as to cause the deposition of moisture upon its sur- 

 face. This hypothesis takes account of the length of descent, because in passing 

 through more air more moisture would be gathered ; it agrees with the fact that 

 the augmentation for given lengths of descent is greatest in the most humid sea- 

 sons of the year ; it accounts to us for the greater absolute size of rain-drops in 



