500 Mr. J. W. L. Glaisher^s Supplementary Remarks 



Wiedemann and Franz*, that the heat-conducting power of 

 metals is directly proportional to their electric conductivity, or 

 inversely as their specific resistance. If w denotes the specific 

 resistance of a metal, C a constant, the heat-conducting power 



W 



Lenzf has found this law verified when K and w refer to the 

 same temperature. In a determination of K in the thermal 



units above chosen, and of w in absolute measure -, — , 



second 



for one and the same iron rod, I obtained for the constant C 

 C = 2458xl04, 



in which the values of K and w referred to the temperature 

 44"-3 C. 



LX. Supplementary Remarks on some early Logarithmic Tables, 

 By J. W. L. Glaisher, B.A., F.R.A.S., Fellow of Trinity 

 College, Cambridge %. 



IN the October Number of the Philosophical Magazine I stated 

 that Decker's work left no doubt "that to him must be 

 assigned the credit of having been the first foreigner who pub- 

 lished Brigo-ian logarithms, an honour which has always been 

 hitherto assigned to Vlacq." This sentence requires some mo- 

 dification, or at all events explanation, as Vlacq was not the only 

 claimant for the honour in question. His rival was Denis Hen- 

 rion, who published at Paris in 1626 a Traicte des Logarithmes, 

 containing Briggs's logarithms of numbers from 1 to 20,000 to 

 ten decimals, and Gunter's logarithmic sines and tangents. Hen- 

 rion^s work has been so rarely met with by the bibliographers 

 that it has become little more than a tradition. It is scarcely 

 ever mentioned by German writers ; and all De Morgan could 

 collect is contained in the following extract : — " (1626) Henrion's 

 ' Logarithms,' Paris. (Dodson, followed by Hutton.) Lalande 

 knew nothing of this work, nor Delambre. All we can learn is 

 from Dechales, who states that Henrion wrote on the propor- 

 tional compasses in (1623), reprinted in (1681), and on the rule 

 of proportion (which we take to be Gunter's scale) in (1626) ; 

 and that the last work contains logarithms of numbers up to 

 2000." 



* Pogg. Ann. vol. Ixxxix. p. 531 ., 



t Bulletin de F Academic Imperiale des Sciences de St. Petershourgy vol. 

 \iv. p. 64. 



X Communicated by the Author. 



