(43) 



EESULTS OF SOME EXPEEIMENTS UPON THE BATE 



OF EVAPOKATION. 



By J. E. Sutton, M.A. (Cantab.). 



(Eead November 27, 1901.) 



Of the dozens of patterns of evaporators designed (and sometimes 

 used) by different inventors, not one has hitherto been unreservedly 

 accepted as a standard. Consequently, in the absence of any 

 authoritative pronouncement, observers have used so-called gauges 

 of all sorts of sizes and all sorts of mountings. Naturally the 

 results differ as widely as the methods, some showing a rate of 

 evaporation fully twice as great as others. Mr. Baldwin Latham, 

 for example, showed that his fine evaporation gauge made of copper, 

 1 foot in diameter, containing 1 foot in depth of water, and 

 floated by means of a hollow copper ring, placed 6 inches distant 

 from the body of the gauge — to which it was attached by radial 

 arms — on a tank 4 feet in diameter and 30 inches deep, gave an 

 annual average evaporation of 19 '95 inches ; whereas a copper 

 pan, 5 inches in diameter and 12 inches deep, standing in air, lost 

 38*19 inches.'" In the Strathfield Turgiss experiments, again, the 

 indicated evaporation for the six months April to Septeml^er, 1870, 

 varied between 20*64 inches from a large iron tank 6 feet square 

 and 2 feet deep, sunk in the ground, to a trifle under 47 inches 

 from a tin can 12 inches deep and 5 inches in diameter, stand- 

 ing upon the ground ; some small pans under cover giving an 

 annual average of about 14 inches at the same time, f " Dr. 

 Brownrigg fixes the evaporation of some parts of England at 



* Presidential Acklress to the Royal ^Meteorological Society. Qiiarterh/ Jounuil 

 Boy. Met. Sue, vol. xviii. p. 55. 

 t British B(ti)ifall, 1889. 



