YALE AGRICULTURAL LECTURES. 139 



inches in 1858 (the wettest year in 40, and one in which there 

 were only 170 fair days) to 32'46 inches in 1856 ; the average 

 of the whole period being 42 inches. 



The time permitted only a cursory allusion to the other 

 aqueous phenomena of dew, frost, and hail. The lecturer 

 pointed out the defects of common thermometers, and the 

 mode of selecting a good one. He remarked that between 

 32 and 212 Fahrenheit it was easy to select an instrument 

 which would indicate the temperature within one or two de 

 grees of accuracy. He exhibited, however, four instruments 

 taken that day from the stock of a dealer, from which he read 

 as follows : 64 ; 62 ; 65 ; and 66. Below 32 common 

 thermometers were generally very unreliable ; the difference 

 amounting near zero often to more than 10. He stated that 

 in old thermometers the point of freezing (32) was found 

 almost uniformly too high, and that the readings of old ther 

 mometers were as a rule too high. This was owing to a per 

 manent displacement of the zero point, partly arising from 

 atmospheric, pressure on the surface of the ball, and partly 

 from the slow contraction of the glass subsequent to the heat 

 ing to which it was subject in filling. 



He gave practical rules for the exposure and observation of 

 thermometers. A thermometer should never be hung against 

 the wall of a house, for the radiated heat makes the mercury 

 rise often as much as 4. It should be placed on a post in the 

 yard. It has been proved that in our country the temperature 

 at 9 A. M. will be just 1 less than the average of the whole 

 day. If our thermometer marks 50 at that hour, we may 

 know that the day will average just 51. The coldest hour of 

 the clay is 7 A. M., and the warmest 2 P. M. 



He concluded by commending to farmers the study of me 

 teorology, as an important element of the practical education 

 on which success in agriculture must depend. 



Mr. SA:NT>FOKD HOWARD, of The Boston Cultivator, gave a 



