YALE AGRICULTURAL LECTURES. 137 



other grains, of the limits of the vine, of maize, etc., was pointed 

 out on a chart, and in this connection the summer climate of 

 British Columbia was alluded to. He also called attention to 

 the marked difference in the winter climates of the two oceanic 

 borders of the continent, as compared with the corresponding 

 latitudes in the interior. 



The Aqueous Phenomena of the atmosphere were next con 

 sidered. The presence of moisture in the air at all times was 

 explained, its amount depending on the temperature. 



That the capacity for moisture is greater as the temperature 

 increases was shown by the following table. 



A body of air can absorb : 



At 32 F. the 160th part of its own weight of watery vapor. 

 " 59 " " 80th " " " " 



" 86 " " 40th " " " ' 



"113 " " 20th " " " 



It will be noticed that for every 27 of temperature above 

 32, the capacity of air for moisture is doubled. From this it 

 follows, that while the temperature of the air advances in an 

 arithmetical series, its capacity for moisture is accelerated in a 

 geometrical series. 



The lecturer here exhibited various forms of hygrometers, 

 and illustrated their use experimentally : Saussure's hair hy 

 grometer, various hygroscopes, Daniells' condensation hygrom 

 eter, and August's hygrometer of evaporation. He also exhib 

 ited a simple substitute for the costly condensation hygrometer, 

 being nothing but a bright silver goblet or tumbler containing 

 water and lumps of ice. The first condensation of dew on the 

 polished metallic surface is watched for, and the instant it ap 

 pears the difference between the thermometer in the iced 

 water and the air is noted. This gives the dew point, or tem 

 perature at which fog would be produced. 



The mode of measuring the rain fall was also described. 

 One of the simplest rain-gauges was a cylindrical vessel of tin, 

 or copper, furnished with a float : the rain falling into the ves- 



