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 O'l grain 1 . 



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 unstretched. 



