86 MR. W. N. SHAW ON HYGROMETRIC METHODS. 



itself; attached to the second copper coil was a second globe with three necks, which 

 contained a thermometer inserted in exactly the same manner as the REGNAULT 

 hygrometer, and likewise shown in the figure. This sequence, consisting of (l) a 

 copper coil k (fig. 3), (2) a globe containing the hygrometer, h, (3) a copper coil, k', 

 (4) a globe containing a thermometer, t, was simply interposed between the saturator 

 and the aspirator, so that the air passed through the whole series. 



Fig. 3. 



70 ASPIRA TOR 



In order to fit the REGNAULT thimble tightly into the globe it was cemented by 

 means of gelatine to a glass tube, over which it would just slip. This was found not 

 to be quite tight when there was a considerable difference of pressure between the 

 inside and outside, and the leakage might have interfered with some of the observa- 

 tions. The joint was therefore strengthened by lapping the line of junction of the 

 silver and glass with pure india-rubber strip pulled very thin and having each 

 successive layer painted over with benzene. After a sufficient thickness was lapped 

 on, the whole was painted with a solution of india-rubber in benzene and varnished, 

 and no further trouble was caused by any leakage at the joint except in the five 

 experiments noted in Table VI. 



Fig. 4. 



Subsequently a DINES hygrometer enclosed in a cylindrical glass tube, fig. 4, was 

 added to the apparatus immediately following the globe containing the REGNAULT. 

 The metal box, connecting tube, and thermometer of the DINES were detached from 

 the wooden frame in which they are usually mounted. The delivery end of the tube 



