644 Professor T. E. Thorpe [March 4, 



lines were etched, m\ m^, h^, on tLe left limb ; m^, w*, 7c^, on the right 

 limb. The volumes of the limbs between m^ and m^ and between m^ 

 and m* were carefully determined ; these rejiresent the volumes of 

 liquid which flow through the ca2)illarj. The time taken by the level 

 of the liquid to pass from the upi^er to the lower of either of these 

 pairs of marks is the time observed in the experiments. The limb is 

 constricted in the vicinity of the marks, in order to give sharpness in 

 noting the coincidence of the meniscus with the mark. The shape of 

 the limb between the marks was made cylindrical rather than spherical, 

 in order that the contained liquid might the more readily acquire the 

 temperature of the bath in which the glischrometer was placed during 

 an observation. 



It will be seen from the figure that the upper ends of the limbs 

 H^, H'-^ terminate within the glass traps T^, T'^. These traps admit 

 of slight adjustments of the volumes of liquid contained in the limbs, 

 and their use is connected with that of the marks h^ and 1c-. During 

 an experiment the levels of liquid in the two limbs are continually 

 altering. The object of these marks and trajDS is to ensure that at the 

 beginning of any observation in a particular limb the effective head 

 of the liquid contained in the glischrometer shall be constant and 

 shall be known. Let us sujDpose that an observation is to be made in 

 the right limb ; the liquid level in the left limb is just brought into 

 coincidence with the mark k^, when any excess of liquid will flow 

 over into the trap T^ ; hence the effective head of liquid extends 

 from H^ to k^, and is thus known. A similar proceeding is carried 

 out for the left limb observations, using the mark P and trap T^. 

 The marks k^ and k'^ are placed by trial in such positions that the 

 volume from k^ to H^ is almost equal to, but slightly greater than, 

 that from P to H^. The volumes F- H^ and P H^ are the working 

 volumes of liquid used in the observations. 



The general arrangement of the whole apparatus is shown in 

 Fig. 2. A bath B, which for observations at temperatures below 

 100° contains water, and for higher temperatures glycerin, is sup- 

 ported on an iron stand which is placed on a table in front of a 

 window.* The bath is divided into two compartments. The inner 

 compartment is provided back and front with i3late glass walls ; the 

 rest of the bath is made of brass. The outer compartment bounds 

 the inner at the sides and underneath, and is fitted with a tap for 

 adjusting the quantity of liquid which it contains. The brass frame- 

 work carrying the glischrometer, and thermometer T, can be lowered 

 into vertical slots in the lateral walls of the inner compartment ; 

 when thus situated the glischrometer occupies a central position in 

 the bath. The walls of both compartments are provided with guides, 

 along which move stirrers consisting of brass plates pierced with 

 holes, which are attached to suitable rods and cross pieces, and are 

 worked by a small water-motor W M. 



* In practice two baths were used, one containing water, the other glycerin. 



