for Measuring the Expajisions of Solids, Sfc. 269 



from 392° to 572° -00091827: and of iron, from 32° to 212° 

 •001 18203 : from 392° to 572° -00146842, showing an increas- 

 ing dilatation in each when referred to an air-thermometer. 



The bars of the different metals used in the following expe- 

 riments were all exactly 6*5 inches in length. 



Exp. 1. A square bar of platinum j%ths of an inch thick, 

 was carefully arranged in the black-lead register, which was 

 placed in the apparatus represented, upon a diminished scale, 

 at fig. 3. (Plate II.) a is an iron tube about two inches diameter, 

 and closed at the botom : Z> is a black-lead tube closed at the 

 top, and fitted to the mouth of the former by grinding : c is a 

 smaller black-lead tube projecting from the side of the latter 

 near its upper end, and likewise fitted to its place by grinding. 

 The whole forms a kind of alembic, which may be readily put 

 together, and in which mercury may be easily boiled on a 

 common fire, and the vapours collected without loss or an- 

 noyance to the operator. The register was fixed in its place 

 by a wire, so that when mercury was poured into the iron 

 bottle it was prevented from floating. The mercury in this 

 experiment rose a little above half the length of the register. 

 The whole apparatus was then placed upon a fire, and in ten 

 minutes the mercury began to boil : in ten minutes more it 

 freely distilled over; and in ten minutes further the apparatus 

 was removed, the register taken out and allowed to cool. The 

 arc measured upon the scale was in this instance 1° 17'. 



The experiment was repeated, merely having the head of the 

 alembic off, and suffering the mercury to boil freely in the iron 

 bottle for a quarter of an hour. The arc measured was 1° 23'. 



The register was next allowed to float upon the mercury, 

 so that when the head of the alembic was adjusted and the 

 mercury made to boil, it was not immersed in the metal, but 

 surrounded by its vapour: the reading was 1° 16'. A repeti- 

 tion of this arrangement gave 1° 23'. 



In another repetition of the experiment, the time was ex- 

 tended to twenty minutes from the first boiling of the mercury; 

 the reading of the scale was 1° 20'. 



Again ; the time was reduced to ten minutes, and the 

 measurement was 1° 23'. 



In the various repetitions of this experiment the mercury 

 freely distilled over, and the temperature was such, that every 

 })art of the black-lead tubes, in which the vapour circulated, 

 would just scorch, but not blacken, a piece of writing paper 

 held against them. 



The following Table collects these results into one view, and 

 cxhil)ith the expansion denoted by eacii reading, and the mean 

 result. 



Table 



