XVI. ON A NEW REGISTERING BALANCE. 



Alex. P. Anderson. 



In the course of certain experiments on transpiration lately- 

 conducted in the laboratories for plant physiology of the 

 University of Minnesota it became apparent that to ascertain 

 the rate of transpiration for some length of time some self 

 registering mechanism that could be used to record the increase 

 in the weight of the absorber was necessary. With such an 

 appliance the periodicity (if any) in transpiration coald be 

 determined, and a true transpiration curve plotted. After 

 repeated trials and alterations, such a registering balance has 

 been designed consisting essentially of a balance, one arm of 

 the beam of which is lowered by the increase in weight of the 

 calcium chloride absorber. 



As this arm is lowered a circuit is closed and an electro- 

 magnetic mechanism releases a weight which falls on the other 

 arm of the scale beam, or rather into its scale pan. Thus the 

 scale is balanced automatically, after an increase equal to the 

 weight used has taken place. At the same instant that the 

 weight is released it is recorded on the registering cylinder of 

 the recorder, which can be at any distance from the 

 balance itself. The scale and balancing mechanism are 

 enclosed in a case which entirely protects the whole from fall- 

 ing moisture. 



The following detailed description will serve to illustrate the 

 action: The weighing apparatus consists of a platform scale 

 made especially for the purpose, and to fit the registering 

 mechanism. This scale is sensitive to one-fifteenth of a gram, 

 with a capacity of five kilograms. It has abeam eleven inches 

 long, the supports of which are screwed to an iron plate in the 

 bottom of the case, thus making the scale and case practically 

 one and both can be leveled and adjusted together. The brass 

 scale pans are seven inches in diameter and are carried by 

 iDrass supports, attached to the arms of the scale beam. The 

 scale bearings are of diamond steel. 



