92 



SPRING BALANCE. 



[CH. IV 



for demonstrating the loss of weight due to transpiration, 

 and it is probable that it may prove to be useful for 



Fig. 17. Exp. H6. 



research purposes under certain* conditions. A cut branch 

 in a test-tube of water T is suspended , by a wire to a 

 spiral spring S. At P the wire passes through a small 

 hole in a metal plate : at Z' a fine spun glass filament is 

 fastened horizontally to the wire. As T loses weight the 

 index rises and its movement is recorded by means of a 

 horizontal microscope. With the weakest power of our 

 microscope one degree of the ocular micrometer equals 

 0'044!mm.: the following readings (expressed in gradua- 

 tions of the micrometer) were obtained by adding a 



