SMITH. — EXPANSION OF ETHER AND ALCOHOL. 427 



distilled water at a known temperature. The capacity of the dilatom- 

 eter was determined in precisely the same way. The former had a 

 capacity of G4.04 (cm.)', the latter a capacity of 70.32 (cm./. 



The capillary stem of the piezometer, and also that of the dilatom- 

 eter, was calibrated by use of a mercury column, so that the cross 

 section of each of them was accurately known at all points. The 

 capillary tube of the dilatometer, which had a mean cross section of 

 0.01918 (cm.)^ happened to have a very uniform bore, which showed 

 a variation of only about one half of one per cent over a distance of 

 20 cm. The capillary tube of the piezometer, with a mean cross sec- 

 tion of 0.01536 (cm.)*^, showed a variation of about 2 per cent over a 

 distance of 20 cm. 



Brass Jacket. 



In order to have the pressure on the inside of the piezometer the 

 same as that on its outside it was inserted in a rectangular brass vessel 

 which for the sake of brevity will be referred to as the brass jacket. In 

 the course of the whole work two slightly different types of brass 

 jackets were used. As their differences were of minor importance, only 

 one of them will be described. The brass jacket consisted essentially 

 of a rectangular brass box 7 1 cm. long, 1 1 cm. high, and 5 cm. wide, the 

 walls of which were made of strips of brass 0.6 cm. in thickness. In 

 one end of the brass jacket there was a rectangular opening 7 cm. long 

 and 3 cm. wide, through which the piezometer or dilatometer could be 

 introduced. This opening was then closed by the means of two cast- 

 ings, which were separated from each other and from the end of the 

 brass jacket by means of rubber gaskets. These castings, after being 

 firmly joined together and to the end of the brass jacket by means 

 of screws, afforded a conical shaped orifice into which M (Figure 4) or L 

 (Figure 5) fitted snugly. In order to prevent the stopper from coming 

 out under pressure greater than one atmosphere, it was pressed into 

 the conical orifice by means of a disc which, having at its centre an 

 aperture through which passed the capillary stem of the piezometer 

 or the dilatometer and the lead wires of the platinum thermometer, 

 was firmly fastened to the castings by means of four screws. In either 

 side of the brass jacket was a narrow window, closed by thick plate 

 glass used with a rubber gasket, through which observations could be 

 made. Into the top of the brass jacket and near each of its ends was 

 inserted a short cylindrical brass tube. One of these tubes was con- 

 nected to the pressure gauge so as to allow any desired pressure to be 

 applied to the liquid in the brass jacket. The other was for purposes 

 of filling, and was closed with a cylindrical brass cap after the filling. 



