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XVII. Experimental Researches on the Laws of Evaporation and 

 Absorption, with a Description of a new Evaporanieter and Ab- 

 sorbometer. By Thomas Tate, Esq.* 



Evaporameter. 



^T^HIS instrument enables us readily to determine with con- 

 JL siderable precision the amount of evaporation which takes 

 place from a given surface of water at different states of the atmo- 

 sphere. The most direct and probably the most accurate method 

 of determining this consists in exposing a known weight of 

 w r ater, placed in a large shallow pan, to the action of the air ; and 

 then, after the lapse of a certain time, by weighing the pan with 

 the residue of water, the weight of the water which has been 

 evaporated becomes known. This method, however, is not only 

 troublesome, but supplies no correction for the rain or moisture 

 that may have fallen during the period of exposure. The instru- 

 ment which I have constructed not only takes the rain-fall into 

 account, but is also simple in its use, and sufficiently accurate in 

 its indications. It consists of a large glass bell, such as are 

 used for aquariums, B, fig. 1, nearly filled with water, placed 



Fig. 1. 



upon a stout deal board G H ; a glass tube, C E F, divided 

 into linear inches, about 18 inches long, and f^ths of an inch 

 internal diameter, supported on the pillars E H and F G in a 

 slightly inclined pjosition, the extremity F having a rise of about 

 jL in 1, and having its bent extremity E C dipping into the 

 water contained in the glass bell ; a displacement-gauge D, gra- 

 duated into cubic inches and parts of cubic inches, supported in 

 a vertical position by the sliding ring R, with its clamp-screw, 

 so that it may be readily raised out of or depressed in the water 

 contained in the glass bell; a wide graduated tube T, placed as 

 shown in the diagram, to catch the overflow of water 'from the 

 * Communicated by the Author. 



