BRIDGMAN. — MERCURY UNDER PRESSURE. 



427 



fact that the density of the CSa when determined by weighing in it a 

 solid steel cylinder agreed within 1 part in 13,000 with the value found 

 by weighing in it the steel shell with the mercury. 



Five preliminary determinations of the change of volume were made 

 giving results varying from 0.00253 to 0.00257. The chief cause of 



180.990 



(80.560 



TEMPERATURE, ARBITRARY SCALE, 



Figure 24. Shows the readings from wliich was found the change of 

 volume when mercury melts at atmospheric pressure. The scale above and 

 to the left refers to the solid mercury, and that below and to the right to the 

 liquid. The point A indicates the beginning of melting, and the point B 

 shows the completion of melting. 



inaccuracy in these prehminary results was the irregular behavoir of the 

 resistance thermometer. This was due to the defective insulation of 

 the enamelled wire used in these first experiments. Replacing the 

 enamelled wire by silk-covered wire gave perfectly satisfactory results. 

 Advantage was also taken of this preliminary work to modify slightly 

 various details of apparatus and procedure. 



Three independent determinations of the change of volume were 

 made with the final form of apparatus. The experimental points of 

 one of these determinations are shown in Figure 24. The mercury 

 was changed for each of these determinations, the total quantity being 

 varied by 10 per cent. The three values found, using the iron resist- 

 ance as the temperature indicator, were 0.002533, 0.002536, and 

 0.002532 cm.^ per gm. The same weighings plotted against the ther- 

 mometer readings (it is to be remembered that this was done merely 

 as a check) gave 0.002533, 0.002537, and 0.00252 respectively. The 

 thermometer points of the last determination were very irregular. 



