ii8 



Journal of Agricultural Research 



Vol. V, No. 3 



pan of the balance (fig. 2). The weight thus added opened the circuit, 

 and a spring restored the block to its normal position, where the pocket 

 was again filled by a ball from the reserve supply. Anderson did not 



Fig. I.— Vesque's automatic balance for measuring transpiration. In this apparatus measured quantities 

 of mercury are added to the receiver on the balance pan to counterbalance the transpiration losses. 



place the plant directly on the balance, but used his apparatus to register 

 the gain in weight of absorption tubes connected with the transpiration 

 chamber. He does not describe the form of the recording apparatus 

 employed. 



Ganong (1905) in his "autographic transpirometer " (fig. 3) combined 

 the ball-dropping and the recording mechanism in a compact and con- 



FiG. 2. — Anderson's apparatus for measurmg transpirat: 



in which steel balls are used as weights. 



venient form, one electromagnet serving both purposes. Steel balls 

 one-fourth of an inch in diameter were employed as weights. Balls of 

 this size approximate i gm. each in weight. The clock was so arranged 



