for Measuring the Expansions of Solids, S)-c. 273 

 Table VII. (Continued.) 



Expansion of Difference 



Expansion of the Metal Bars. Black-lead Register. from Mean. 



Copper absolute -00930 



apparent '00683 



... =-0024.7 ... +-00013 



Tin absolute -01177 



apparent -008 14 



... =-00363 ... + -00129 



Zinc absolute -01593 



apparent -01454 



... =-00139 ... — -00095 



Lead absolute -01542 



apparent -01223 



... =-00319 ... + -00085 



Brass absolute -01045 



apparent -00799 



... ='00246 ... + -00012 



Gold absolute -00794 



apparent -00552 ... =-00242 ... + -00008 



Silver absolute -01034 



apparent -00814 



... =-00220 ... —-00014 



Mean -00234 



In five instances out of these nine, the difFerence of the 

 expansion of the black-lead from the mean does not exceed 

 To^^o o<^ths of an inch, two being in deficiency, and three in 

 excess : and it is worthy of observation that they are the metals 

 whose dilatations have always been considered the most re- 

 gular, and concerning which there is the least difFerence of 

 authorities, viz. gold, silver, platinum, copper, and brass. 

 The greatest difFerence is in the tin, which amounts to nearly 

 TuJuo^ths of an inch in excess ; and it is more than probable 

 that the ab.solute expansion of this metal has not hitherto been 

 obtained with sufficient precision, and that it even varies in 

 different states. I shall return to this subject in the second 

 part of this paper, which I reserve for a future communication; 

 in which I hope to be able to lay before the Society observa- 

 tions and tables of the dilatations of metals to their meltino- 

 points. It is my intention in this first part to touch no furthe*r 

 upon the subject of expansion than is suflicient to establish 

 confidence in the pyrometer as a measure of heat. 



Another confirmation of the precision of these observations 

 may be derived by calculating the expansion of the black-lead 



N.S. Vol. 10. No. 58. Oct. 1831. 2 N recrister 



