44 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



venient places for observation. The frame for the glass at the top is 

 removable to provide for the extension of the house upward when 

 very long tubes are to be accommodated. The various windows and 

 doors are made to close tightly against rubber cushions, or the cracks 

 between them and the frame- 

 work are covered with surgeons' 

 tape. The tubes through which 

 the wires enter the house are, 

 however, left more or less open 

 to provide for equalization of 

 atmospheric pressure. 



During the past year or two, 

 the more exacting parts of the in- 

 vestigation of manometers have 

 been carried out in the bath seen 

 in Figure 45. This bath is am- 

 ple enough to accommodate the 

 steel block, the tapper, and all 

 other accessories required for a 

 determination of capillary de- 

 pression, or of nitrogen volume, 

 and for the comparison of mano- 

 meters; and in it temperatures 

 can be maintained for long per- 

 iods which are constant to 0.01°. 



Plate 2 shows the type of 

 cathetometer used, and under it 

 a specimen of the devices by 

 means of which the requisite 

 degree of steadiness for all the 

 instruments is secured, notwith- 

 standing their location in the 

 third story of the laboratory. 

 The foundation for the catheto- 

 meter consists of two heavy 



WOOden brackets. One end Of Fig. 25.— Improvement in cathetometers for the fine 

 the horizontal timbers is buried adjustment of the telescope which Jo serves as a 



n i 1 • i substitute for the micrometer eye-piece. 



in the thick brick wall behind , . _ ± „ ... , +WbV «. «,h twa^d— 



(a) Set-collar with upper and thicker end threaded — 

 the house, While the descending thread 1 millimeter pitch; (b) nut running over 



timbers pass through the floor i^'^ vadxu ^^i!!^^ ( SSS t '£a! d 



r & to s i eeve carrying telescope, and resting on {&). 



and enter the same wall in the 



room below. There is nowhere contact with a floor or with a parti- 

 tion wall. Two such brackets are required for a cathetometer and 

 three for a bath. 



In Figure 25 is shown an improved arrangement for fine adjustment 

 of the height of the telescope, and for reading fractional parts of a milli- 



