356 LORD KAYLKICH ON THK COMl'KKSSIBIUTY OF (1ASKS 



that in the reservoirs by pinch-cocks, and the adjustment of the supply is effected by 

 squeezing the hoses. As explained in my first paper, the final adjustment must be 

 made by squeezers which operate upon parts of the hoses which lie flat upon the 

 large wooden tray underlying the whole. 



The Side Apparatus. 



The use of this was fully explained in my former paper. By the employment of 

 manometric gauges we are enabled to dispense with scales and cathetometers ; but 

 since (save as to a small temperature correction) the pressures are defined beforehand, 

 the adjustment is thrown upon the volume. The variable volume is introduced at 

 the side tube JK, which, with its associated bulb, allows of the elimination from the 

 results of the volume which cannot be directly gauged, including that over the 

 mercury in the lower chamber of the right-hand manometer when set. The tubes 

 above and below the bulb were calibrated in the usual manner.* It should be 

 remarked that the diagram shows the mercury in the side apparatus in a position 

 suitable for a measurement at the doubled pressure, while in the rest of the apparatus 

 the position of the mercury corresponds to the single pressure. 



General Sketch of Theory. 



It will be convenient to repeat this, nearly as given in the former paper. To save 

 complication, it will be supposed that the temperature is constant, not only throughout 

 the whole apparatus at one time, but also at the four different times concerned. 



Vj = volume of two large bulbs H, H together between GG, II (about 633 cub. 

 centims.). 



V 3 = volume between CJGG (the ungauged space). 



V 4 = measured volume on upper part of JK from highest mark J downwards. 



V 5 = measured volume, including bulb of side apparatus, from highest mark J 

 downwards. 



Pj = smaller pressure (height of mercury in right-hand manometer). 



P 2 = larger pressure (sum of heights of mercury in two manometers). 



In the first pair of operations, when the large bulbs are in use, the pressure P t 

 corresponds to the volume (V,+V 3 +V 5 ), and the pressure P 2 corresponds to 

 (^V 1 +V 8 +V 4 ), the quantity of gas being the same. Hence the equation 



* The whole of the apparatus was made under my instructions by the late Mr. GORDON, who also took 

 a large part in the observations. I take this opportunity of recording my indebtedness to his faithful 

 assistance over a long series of years. 



