THE FARMER AT HOME. 149 



weight of nearly five hundred pounds. It is stated that he has done 

 nuch to improve the Essex ; and, that the pigs are much sought 

 throughout the British realm. 



ESSEX HOG. 



EVAPORATION. The volatilization of a fluid by means of 

 heat, with access of air, in order to diminish its fluidity, or to obtain 

 any fixed salts it may hold in solution, or diminish the quantity of a 

 residuum. In this manner, the water of the sea is evaporated, and 

 the salt obtained, and decoctions made into extracts. Evaporation is 

 one of the great chemical processes, by means of which Nature sup- 

 plies the whole vegetable kingdom with the dew and rain necessary 

 for its support. Hence, it takes place at all times, not only from the 

 surface of the ocean, but also from that of the earth. Nor is it con- 

 fined to these ; it is even carried on from the leaves of trees, grass, 

 and flowers, with which the earth is covered. Great part of the 

 water which is thus raised, descends again during the night, in the 

 form of dew ; being absorbed by those vegetables which yielded it 

 before. 



One of the most beneficial effects of evaporation, is to cool the 

 earth, and prevent it from being too much heated by the sun. This 

 property of producing cold by evaporation, has but lately been 

 observed by chemists, who have accordingly availed themselves of it 

 in its fullest extent ; though their mode of procuring cold, by means of 

 those expensive fluids, ether and spirits of win;, can only be employed 



