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XXIII. — Remarks on the Theory of Rain. 

 By Mr. Joseph Baxendell^ F.R.A.S. 



Eead March 29th, i860. 



It has been well established by numerous carefully con- 

 ducted experiments, that the quantity of rain received by 

 a gauge placed on or near the ground is almost invariably 

 greater than that received by a similar gauge placed at a 

 greater elevation in the immediate neighbourhood ; and, in 

 explanation of this remarkable fact, meteorological writers 

 have generally adopted the hypothesis advanced by Pro- 

 fessor Phillips [Report of the British Association for 1833, 

 p. 410), "that the whole difference in the quantity of rain 

 at diflferent heights above the surface 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 sur- 

 rounding medium, as to cause the deposition of moisture 

 upon its surface." In support of this hypothesis. Professor 

 Phillips remarks "that it takes account of the length of 

 descent, because in passing through more air more mois- 

 ture would be gathered j it agrees with the fact that the 

 augmentation for given lengths of descent is greatest in 

 the most humid seasons of the year; it accounts to us 

 for the greater absolute size of rain-drops in the hottest 

 months and near the ground, as compared with those in 

 the winter and on mountains ; finally, it is almost an 



