BY HEAT OF METALS AND ALLOYS. 863 



The copper was slightly gilded to prevent the action of the water on it ; the water 

 being reboiled before each weighing to drive out any absorbed air. The values given 

 in the third column express the volume of the copper in cubic centimetres, and arc 

 deduced from the observed loss of weight in water W, as described (p. 245) in the paper 

 already quoted. Calculating formulae to express the volumes of copper at different 

 temperatures, we find for 



No. 1. 

 V,=3-95680(l + 0-00004645« + 0-0000000336^2), or if V„=l, then V.„,=l-004981 ; 



No. 2. 



V,= 3-95655(l + 0-0000468l!f+0-0000000300^2), or if V„=l, then V,o«=l-004981, 



formulae agreeing closely with that deduced from the determination of the linear expan- 

 sion of the copper rod, namely, 



V,=V„(l + 000004665iJ+0-0000000366if2), or if Vo=l, then ¥,,,= 1-005031. 



This memoir may be divided into two parts : — 

 I. On the Expansion ly Heat of the Metals. 

 II. On the Expansion hy Heat of Alloys. 



I. On the Expansion hy Heat of the Metals. 



The metals employed for these experiments were purified in the manner described in 

 a former paper *, and cast in a well-smoked mould, which gave the casting the shape 

 of a double wedge, as shown in fig. 7f, Owing to the action of the water on some of 

 the metals and alloys, the castings had in some cases to be A'arnished or gilded, the 

 latter method being more generally used. To prove that the gilding or varnishing had no 

 influence on the results, some of those metals on which water has no action were var- 

 nished or gilded in the one series and not in the other (Series Nos. 3 and 4, 14 and 15, 

 11 and 12). 



The disposition of the apparatus and the method of observation was the same as 

 described in the paper " On the Expansion of Water and Mercury." 



Sometimes observations were made commencing at the highest temperature, and 

 cooling down without boiling out the water between the determinations made at the 

 different temperatures. (The series made in this manner will be headed once boiled.) 



At others the observations were first taken at the lowest temperature, the water re- 

 boiled, then those at the highest temperatui-e, and afterwards on cooling those at the 

 intermediate one (twice boiled). 



And again, at others the water was reboiled between each set of observations (thrice 

 boiled). 



It may be as well to point out some of the causes of failure in this method of deter- 



* Philosophical Transactions, 1860, p. 177. 

 t Philosophical Transactions, 1866, Plate XX. 



6a2 



