I. AGRICULTURE AND RURAL ECONOMY. 381 



I. AGRICULTURE AND RURAL ECONOMY. 



DETECTION OF ORGANIC MATTER IN THE ATMOSPHERE. 



Mr. A. H. Sraee closes a glass funnel by drawing out its 

 neck to a fine point, places it in a stand, and fills it with ice. 

 He allows the aqueous vapor that condenses from the atmos- 

 phere on the outside to drop into a vessel, and measures the 

 quantity thus accumulated in a given time, and determines 

 the ammonia by one of the usual methods. By this means, 

 called "distillation by cold," substances that are decomposed 

 by high temperature can be condensed. The perfume of 

 flowers, for example, cau be distilled by placing them under 

 a bell-jar with the funnel. 15 C, 1873, 14. 



PROTECTING VINEYARDS BY ARTIFICIAL CLOUDS. 



The idea was suggested, not long since, of protecting the 

 vineyards of France during critical periods of cold by the 

 formation of artificial clouds that should prevent excessive 

 radiation from the soil, and the experiment W' as recently tried 

 at Suresnes. In a vineyard of about 50 acres there were 

 placed 360 iron vessels containing a heavy oil. All these be- 

 ing lighted at once, a thick black cloud was soon interposed 

 between the vines and the sky. During clear and calm 

 weather these clouds remain in place, and thus perfectly an- 

 swer the purpose. The expense of this operation, including 

 pots, oil, and labor, was estimated at about 40 cents per 

 acre, and those who witnessed the experiment were assured 

 of its value and its practical availability. 18 A, March 21, 

 1873,9. ^ 



COMPARATIVE TEMPERATURE OF SOILS. 



A memoir was published by Becquerel, in November, 1872, 

 upon the comparative temperature of soils at a given depth, 

 and of the same composition, but the one covered with a 

 short vegetation, and the other bare and sandy. The obser- 

 vations were made with the electric thermometer, by which 

 it was shown that, from the autumn of 1871 to the summer 

 of 1872, the mean temperature, at a depth of from 2 inches 



