VOL. LXXXII.] PHILOSOPHICAL TKANSACTIONS. 273 



mometer hanging between them that was used in our experiments by weight, I 

 immersed them in a large quantity of water brought to the temperature of 6o", 

 the one quite, the other nearly, to the height of the fluid in the stem. In this 

 water they were suffered to continue till they had arrived at that temperature, 

 when it was observed that the spirit in the tube of the long instrument stood at 

 O, or the commencement of the scale, and the spirit in the tube of the short 

 instrument stood at -toVb-o- above O, which I shall in future for shortness call 1.5, 

 and which it is evident must be applied with the sign -f- or — to the quantity of 

 expansion or contraction rend off from above or below O, as the case may require. 

 They were then cooled down to 30° of temperature, when the spirit in the long 

 instrument was found to stand l65, and that in the short instrument l63.5 be- 

 low O. They were again brought to the temperature of 6o°, when the spirit in 

 the long instrument was foimd to stand 0.5 below 0, and in the short instrument 

 1.5 above as before. They were then heated to 100°, when the spirit in the 

 long instrument stood at 231, and in the short instrument at 233.5 above O. I 

 brought them again to the temperature of 6o°, when the spirit in the long instru- 

 ment was found to stand 3 below 0, but in the short instrument 1.5 above O as 

 before. 



It appears from these experiments, that the contraction of the spirit, by the 

 long instrument, for 30°, that is, in cooling down from 6o° to 30°, is l65; but 

 in heating it up again to 6o°, it was found not to stand at O, as before, but 0.5 

 below; therefore the expansion will be only 164. 5, the mean is l64.75. The 

 expansion, on heating up from 60" to 100°, will be 231 + 0.5 = 231.5; but on 

 cooling down from 100° to 60° again, the spirit was found to sink 3 below 0, 

 therefore it will be 231 + 3 = 234; the mean 232.75, and the total expansion, 

 from 30° to 100° = 397.5; differing from ours, in defect, by 0.05 of a division. 

 But the two methods of heating from 6o°to 100°, and cooling from 100° to 60° 

 again, differ 2.5 divisions, or so many 10,000th parts of the whole. 



The contraction from 6o°to 30°, by the short instrument, appears to be 163.5 

 -J- 1.5 = 165, and the expansion, on heating up again to 6o°, the same; from 

 60° to 100° it was found to be 233.5 — 1.5 = 232, and the contraction in cool- 

 ing down again from 100° to 60° the same; the total expansion 307, differing 

 from ours 0.55 of a division, in defect. After the above experiments, the instru- 

 ments were emptied of the spirit ; and another day, preparatory to a repetition 

 of the experiments, they were charged again with some of the same spirit that 

 was used before, and the results found to be as follow. 



Having brought them to the temperature of 6o°, I found the spirit in the long 

 instrument to stand 3 above 0, and in the short instrument 5 below O. They 

 were then cooled down to 30° of temperature; when the spirit in the long in- 

 strument was found to sink to 161.5, and in the short instrument to 167. 5. 



voL.xvn. N iv 



