262 PROCEEDINGS OF THE AMERICAN ACADEMY 



Investigations on Light and Heat, made and published wholly or in part with 

 Appropriation from the Eumford Fond. 



XIX. 



ON THE THERMAL CONDUCTIVITY OF CAST IRON 

 AND OF CAST NICKEL. 



By Edwin H. Hall. 



Presented June 15, 1892. 



In" the year 1890, having occasion to construct a thermopile of 

 nickel and cast-iron, for experiments upon cylinder condensation 

 in steam-engines, I wished to know approximately the ratio of the 

 thermal conductivities of these two metals. To my surprise, I 

 could find nothing in the books examined concerning the thermal 

 conductivity of nickel. As to the same property in iron there 

 was considerable information in print, but different experimenters 

 had found very different values. I therefore determined to seek 

 the information which I needed by experiment, following the well 

 known method of Forbes and of Tait, — a study of the permanent 

 gradient of temperature along a bar heated at one end, in a room 

 of constant temperature, and of independent observations on the 

 rate of heat emission from a bar of the same material in the same 

 room. Forbes and Tait both used a shorter bar for the emission 

 experiments than for the steady flow. I used the same bar for both 

 parts of the work. My results, though claiming no great accuracy, 

 are of some interest to the scientific world, as giving an approximate 

 value for the thermal conductivity of nickel and of cast-iron. 



I had two bars of cast-iron made, each, when finished and thinly 

 nickel-plated to prevent rusting, about 92 cm. long and 2.52 or 

 2.53 cm. in width and thickness. One was of ordinary Southern 

 cast-iron, brittle in quality, specific gravity 7.06; the other was 

 of so called gun-iron, specific gravity 7.18, which is very much 

 tougher than ordinary cast-iron. A number of castings were made 

 for the gun-iron bar before one was obtained that was reasonably 

 free from blow-holes. No such difficulty was experienced with the 

 other iron. 



