COMPARISON OF PLATINUM AND OAS THKKMOMKTKKs. 83 



\\i-re protected from the heating ertect of the tailing-point apparatus by surrounding 

 sleeves of thin copper, traversed by a current of cold water. The temj>erature was 



olpsrrvrd IPV Ml. Mils of ;i sui.-ill t 1 1. -Ill n .1 1 id ( -| |p|;ic.-<l \\ith its I, nil. ill ..Me of the s|,-.-\i-s. 



The temperature of ebullition of the water wa deduced from the barometric 

 pressure, observed every 3 minutes, on the auxiliary barometer No. 3 of the Bureau, 

 placed in a neighbouring room, the necessary corrections being of course applied. 



The following example, which is one of the observations of May 13, will suffice to 

 illustrate the course of the operations. 



DETERMINATION of the 100-point. 



The total volume of the "dead space" taing 445-10 cub. millims., the part 

 surrounded by the sleeves, whose volume was 74'76 cub. millims., had the tempera- 

 ture 12'8 indicated in the last column on the right. For the rest of the "dead 

 space," of volume 366*34 cub. millims., we have adopted the temperature 13*77 indi- 

 cated by the auxiliary thermometer No. 4365. 



The excess of pressure of the vapour over the barometric pressure is measured by 



M 2 



