322 On liain-Gauges 



I would not have ventured to state any thing on this ah'eady 

 agitated subject, without fii'st being possessed of at least twelve 

 months' observations punctually made on the quantity of rain 

 collected in each gauge. With this advantage I may perhaps 

 be enabled to handle the question in a different manner from 

 what has hitherto apjieared. It is the possession of these ob- 

 servations that must serve as an apology fcr my presuming to 

 publish the results, with remarks that were made progressively 

 during the before-mentioned period. 



The question now is. What are the causes of the redundant 

 quantity of rain being generally collected in the lower gauge ? 

 Various are the opinions upon this subject: the two chief ones 

 are these, which seem to militate in the general principles 

 against each other. 1st. That some portion of the receiving 

 surface of the upper gauge is deprived of its rain, by strong 

 drifting currents of air that carry it to another place ; and 

 the deficiency is grounded in a great measure on the particu- 

 lar height of the gauge from the ground, and the sine of the 

 rain's inclination, as influenced by the velocity of the current 

 that accompanies it. Or should the rain fall perpendicularly 

 to the mouth of the gauge (with or without wind), it will re- 

 ceive its due proportion. — 2d. That the quantity of water re- 

 ceived by a rain-gauge is totally independent of the general 

 inclination of the rain, which is represented by diagrams, both 

 in regard to the drops of rain falling in parallel and curved 

 line : so that the obliquity of descent is not considered as 

 having any relation to the quantity of rain which the gauge 

 receives. 



Both these theories having been advanced without any ac- 

 companying results of rain caught in two gauges placed at dif- 

 ferent heights, they may each be right and each be wrong. 



I will now state my opinion as concisely as possible, and ge- 

 nerally from the meinoranda I made at different times during 

 the 12 months; but wheUier my conclusions are right or 

 ■wrong, they will be for the decision of those who are more in- 

 timately acquainted with the subject than myself. 



In steady rains, with calms, or light airs that do not turn the 

 rain out of a perpendicular or down-right course, I have gene- 

 rally found that the quantity in each gauge was nearly equal, 

 and sometimes the same, particularly when the air was natu- 

 rally dry, or not sf.turated with thick haze or damp mists. 

 But when the rains were accompanied with strong gales of 

 wind, whose velocity was at from 50 to 60 miles an hour, from 

 any point of the compass, then the difference of rain in the 

 upper and lower gauge was perceivable on pouring it out into 

 the graduated glass gauge. This difference seeming to depend 



on 



