42 



IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



It will be seen, therefore, that t^ depends upon the radius of 

 the cylinder, ^ on the length, A and B on the initial conditions. 



In table 1 are given the dimensions of commercial tin cans 

 Nos. 1, 2, 21/^ and 3, together with the values of m and ^ cor- 

 responding. The values of A and B computed from the relations 

 already given are appended. 



TABLE I. 



APPROXIMATE EQUATION. 



After considerable time has elapsed all terms after the first 

 in each bracket in equation (6) become negligible and the equa- 

 tion takes the simple form 



-A:(M?-fX?)< 



v = VoAiBie 



-(7) 



In the preceding paragraphs the temperature of the bath was 

 considered to be zero so that Vg represents the initial algebraic 

 temperature difference between the bath and the contents of the 

 can. Expressed in terms of thermometer readings the equation is 



v'=v^-\-A,B,Voe '^ (S) 



Vq being the negative for heating and positive for cooling. The 

 use of this equation makes unnecessary any shifting of tempera- 

 ture scales. In this e(iuation v^ represents the variable tempera- 

 ture and v'' the temperature of the bath. 



