OF IRON, COPPER, AND GERMAN SILVER. 



553 



T 2 , we obtain an estimate of the number of units of heat flowing past the 

 section represented by the next value of x, viz., os 2 . From the area of the 

 statical curve of cooling we derive another estimate, generally less. The 

 difference between the two is the quantity of heat carried off by the cooling 

 bath at the end of the bar. It is to be noted that (as the error, if any, in the 

 values of the tangents, is usually such as to make them alternately too large 

 and too small) where the estimates of this quantity vary, a process of averages 

 is, within certain limits, permissible. 



The following table gives the rate of surface loss, or cooling, for the four 

 metals experimented upon. Those for each metal are the mean of several 

 cooling experiments : — • 



Rates of Cooling. 



Temperature 

 Excess. 



Iron. 



Corjper (Crown). 



Copper (C). 



German Silver. 



°C. 



5 





•047 







10 



11 



•116 



13 



•145 



20 



•26 



•28 



■28 



•32 



30 



•43 



•465 



•46 



•51 



40 



•61 



•66 



•64 



•73 



50 



•807 



•85 



■83 



•94 



60 



10 



1-04 



103 



117 



70 



1-19 



1-25 



1-235 



1-37 



80 



1-405 



1-466 



1-45 



1-62 



90 



1605 



1-7 



1-68 



1-88 



100 



183 



1-927 



1-91 



214 



110 



2-04 



216 



215 



241 



120 



2-28 



2-39 



2 39 



2-7 



130 



251 



263 



2-63 



2-97 



140 



2-77 



2-87 



2 88 



3-25 



150 



3-02 



3-14 



315 



354 



160 



3-28 



338 



343 



3-84 



170 



356 



3665 



372 



4-14 



180 



3815 



3-98 



404 



4-46 



190 



411 



431 



4-4 



4-79 



200 



4-4 



466 



4-75 



511 



210 



4-7 



4-98 



511 



5-43 



220 



5 03 



533 



5-465 



5-77 



230 



537 



5-57 



5-84 



611 



240 



5-74 



5-89 



62 



6-42 



250 



612 



6-22 



6-57 



6-78 



260 



6-55 



6-58 



695 



715 



270 



6-93 



6-92 







The following table shows the result of dividing the rate of cooling in 

 copper (Crown), by that of iron at the same temperature. The column of ratios 

 show that the specific heat of copper rises more quickly than what has been 

 allowed for in the final deduction of conductivity. This, of course, by increas- 

 ing the areas, would increase the conductivity at the higher temperatures. 



