60 



BURTON EDWARD LIVINGSTON 



devised the instrument for agricultural experimentation, but 

 even his publication seems not to have aroused biological workers. 

 The present writer 14 again, also independently, devised the same 

 instrument in the summer of 1904. Since that time, as has been 

 remarked, the literature of atmometry has developed very rap- 

 idly in biological connections. 



1 1 1 1 1 1 1 , i i i 1 1 1 1 1 1 1 1 1 1 1 , i i i i 1 1 1 1 1 1 1 1 



Fig. 6. Diagram showing essentials of potoineter mounting of the porous 

 cup atmometer. R, reservoir, from which water is drawn through tube (E); 

 I, air-bubble index in E; Sc. graduated scale. T, tube from higher supply, from 

 which water is admitted to drive index bubble back, controlled by cock. Porous 

 cup (D) is mounted as in figure o. 



The porous cup surface may be derived, for the sake of a clear 

 picture of relationships, from Bellani's porcelain plate. If we 

 conceive this plate to be bent downward at its edges and extended 

 until it forms a hollow porous clay cylinder, closed above and 

 connected by a non-porous tube to a reservoir of distilled water 

 at a lower level, we have the essentials of the porous cup. The 

 cavity of the cup is filled with water, which is thus in direct con- 



11 Livingston, loc. tit., 1906. 



