I9IS-] 



RECENTLY HARDENED STEEL. 



155 



thermometer T, easily read to hundredths of a degree, indicates the 

 temperature of the air space. 



Air Space 



Granulated Cork 



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■iiiriDiiinTTTT 



T] > 



>. 



W--ysm 



CO.. 



iiSv 



^"w~ 



fr/iiiiiii/iniiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiii/iiii/iiiini/iiiiiinii. 



n 



Granulated G)rk 



m 



Air Space 



H 



Fig. I. 



Returning now the core of the apparatus : A' is an air-tight cylin- 

 der of thin copper, six inches high and two and a half inches in 

 diameter, provided with an open half-inch axial tube also of copper. 

 A small round opening at the top of A' permits the introduction of 

 a weighed quantity of water, after which the opening is tightly 

 corked to prevent any change of temperature by evaporation of the 

 water. B' is another copper cylinder just like A' except that it has 

 a removable top to permit the introduction of the substance whose 

 thermal behavior is to be investigated. The high thermal con- 

 ductivity of these copper cyHnders prevents temperature stratifica- 

 tion within them. The Dewar jars are filled above the copper cylin- 

 ders with layers of felt, and granulated cork, and covered with 

 waxed cardboard carefully sealed on to prevent temperature dif- 



