12 Mr Stevenson on the Defects of Baht-Gauges* 



which opposed their passage, and so will continue to pierce 

 the successive strata, and to augment in size as they ap- 

 proach the ground. 



It evidently follows from these considerations, that the lower 

 any stratum is, the larger will be the average size of the drops 

 composing it, and the greater will be the augmentation of the 

 drops by which it is penetrated. 



This hypothesis seems to explain not only why the whole 

 fall of rain, but also why the increment received in falling 

 through a given height, is greater the nearer the place of ob- 

 servation is to the ground. It also explains why the differ- 

 ence between the indications of the upper and lower rain- 

 gauges is greater in winter than in summer. For as the total 

 increment at any elevation will evidently be as some function 

 of the space through which the rain has fallen, that is, of the 

 height of the cloud, where it was formed, above the gauge ; 

 and as the ratio of the spaces through which the rain descends 

 to two gauges having a constant difference of elevation will 

 necessarily be more unequal when the clouds are low than 

 when they are high, it follows that the difference between the 

 quantities of rain received by these gauges will be greater in 

 the former than in the latter case ; but Dr Dalton's table* of 

 Mr Crosthwaite's observations, shews that the clouds are 

 lower in winter than in summer ; hence the hypothesis is in 

 accordance with experience in this respect also. 

 Edinburgh, Xdth April 1842. 



Observations on the Defects of Bain-Gauges, with description 

 of one of an improved form. By Thomas Stevenson, Civil 

 Engineer. Communicated by the Royal Scottish Society 

 of Arts, t 



Although the subject of the fall of rain in any district of 



* Dalton's Meteorological Essays, p. 41. 



t Bead before the Royal Scottish Society of Arts on 14th Majch 1842. 



