ACCESSORY APPARATUS. 57 



once sufficiently strong to stand the weight of the individual members of 

 the absorbing system and of the oxygen cylinders and at the same time 

 sufficiently sensitive to note a slight increase in weight with great accu- 

 racy. The heaviest individual members of the absorbing system are the 

 water-absorbers, which weigh, after the absorption of one-half kilogram 

 of water, not far from 16 to 18 kg. The balance now in use for this 

 purpose was obtained from the firm of Dr. Robert Muencke, of Berlin, 

 through the Bausch & Lomb Optical Company, of Rochester, New York. 

 It is shown in figure 21. 



The water and carbon-dioxide absorbers and oxygen cylinders are 

 too large to be placed directly upon the balance-pan for weighing ; con- 

 sequently the balance is so mounted that it is possible to suspend each 

 separate member on a wire fastened to one arm of the balance. As is 

 shown in figure 21, the balance is mounted on a heavy shelf fastened 

 securely to the brick wall. The left-hand hanger of the balance has 

 been removed and is replaced by a phosphor-bronze wire which extends 

 through a hole in the bottom of the balance-case, and is provided with 

 hooks or loops for suspending the objects to be weighed. 



Since changes in weight are here desired, rather than absolute weight, 

 the larger part of the weight of these objects is balanced with lead coun- 

 terpoises. The glass front of the balance-case can be raised and the 

 counterpoises added or removed as desired. 



To prevent the effect of air currents along the floor, the lower part of 

 the balance, i. e., the portion beneath the shelf, is inclosed as a closet. 

 The framework, however, does not come in contact with the shelf, there 

 being a small air gap between to eliminate the transmission of vibration 

 from the floor to the shelf. The front of the closet consists of two doors, 

 one of which is removed in figure 21. To provide illumination a glass 

 window is placed in the left-hand side, and the whole interior is painted 

 white. On dark days or during the night an electric light is inserted. 



A small piece of plate glass is set in the shelf immediately in front of 

 the balance in such a way that the upper surface of the glass is just 

 flush with the top of the shelf. After the doors of the closet have been 

 closed it is possible for the assistant to look through this glass and see 

 that the object to be weighed is freely suspended. 



The phosphor-bronze wire by which the objects are suspended is 

 permanently fastened to the hanger on the left-hand balance-arm. The 

 lower end is provided with a swivel, to which two wires with small 

 hooks on the end are attached. These hooks can be conveniently 

 attached to the handles of the water-absorbers. (See fig. n.) 



In weighing these heavy objects it was found much more convenient 

 to place them first on a small platform which could be raised sufficiently 



