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DRS. J. A. HARKER AND P. CHAPPUIS ON A 



its capacity and pressure coefficient and the necessary new determinations of the 

 " dead space." 



(M) Capacity of the Porcelain Reservoir. 



This was determined by weighing the reservoir empty, and filled with water at 0. 

 The following are the results of the weighings made : 



The volume occupied by this mass of water at C. is 



V = 165-393 cub. centims. 



This value has been taken as the total capacity up to the extremity of the capillary 

 tube, part of which is included in the " dead space." 



(b) Dilatation of the Porcelain. 



The porcelain reservoir, carefully dried, was connected to the mercury pump, very 

 thoroughly exhausted, and then filled with mercury in vacua. To the end of the 

 capillary was cemented a glass tube about 1 millim. internal diameter, divided into 

 millimetres, whose calibration corrections and internal volume had been previously 

 determined. The whole being placed in melting ice, the level of the mercury was 

 adjusted to a point on this tube, which was carefully noted. Bringing the whole after- 

 wards to 100, the amount of mercury which escaped was determined by weighing, the 

 necessary corrections being applied to reduce the reading of the meniscus to its 

 original position. 



Four determinations were made by this process of the apparent dilatation of 

 mercury in porcelain between and 100, and a few series of observations were 

 taken at intermediate temperatures. These measurements, about which it is not 

 necessary to enter into further detail, gave after all reductions the following results : 



