CH. IV] SPRING BALANCE. 101 



tions of the micrometer) were obtained by adding a 



Fig. 19. Exp. 116. 



decigram at a time to a scale- pan suspended to the 

 spring, 



7-5°, 7-5°, 7•3^ 7-2=, 7•0^ 7-5°, 7-2«, 7'3°, 7-5°, average 7-3°. 

 When the whole weight was put on at once the index 

 moved through 66° of the micrometer, giving 7*3° as the 

 calculated value of 0*1 gram^ 



When a transpiring plant is suspended the loss of 

 weight may be read every 5 minutes with less disturbance 

 to the plant and with less labour to the observer than 

 with a balance. 



1 The springs we use are made by Salter of Birmingham : they are 

 about 5 cm. in length, when uustretched. 



