6M Mr. FoweWs Appendix toM, RamotuVs Instructions [Nov, 



Pressure. Temperature, Laplace. Trembley. 



0-758 m. 12-5° 1 : 11030-85 1 : 11045-379 



17-6 1:11240'9()3 1:11277-30 



Kirwan. Shuckborough, 



1 : 11033-06 1 : 11053-25 



1; 11268-08 1:11248-84 



Brisson has determined the specific gravity of mercury at 

 17-5° to be 13-5681, that of water being J. 



The same philosopher has also given from the best experi- 

 ments the weight of atmospheric air at 12-5°, and that of water 

 at different temperatures. 



A cubic decimetre of air at the pressure of 



0-758 m. and at the temperature 12-5®, 



weighs, according to him 1-2319025 gr. 



The same volume of water at 12*5° weighs in air 998*064125 



Thence the weight of the water in vacuo = 999*2960275 



On the other hand, a cubic decimetre of water at 18*75° 

 weighs in air of the same temperature 997*445669 gr. Suppos- 

 ing the dilatation lo be nearly uniform vvithin the limits of tem- 

 perature here considered, at 17*5°, the volume of water will 

 weigh in air 997*569444 gr. 



From these experiments it results on the one part that the 

 pressure being 0*758, and temperature 12*5°, the weight of air 

 IS to that of water in vacuo as 1 : 811 . 1814. On the other 

 hand, it results that mercury of the temperature 17*5° weighs 

 13535*12 gr. 



Now these ratios being at 5°, difference in temperature cannot 

 be compared without reference to what we know of the dilatations 

 of mercury and air ; namely, by reducing the mercury to 1 2*5°, 

 or the air to 17*5° ; but the authors of the four formulae above 

 analyzed do not agree in the law of these dilatations. The 

 different results deduced from these experiments, according to 

 the dilatations assumed by each author, are as follows : 



Pressure. Temperature. Laplace. Trembley. 



0*758 m. 12*5° 1 : 11010*86 1 : 11010*883 

 17*5 1 : 11214-128 1 : 11236-39 



Kirwan. Shuckborough. 



1:11009-85 1:11010-883 



1 : 11239-88 1 : 11210-765 



He considers the results at 12*5° most deserving confidence, and 

 that Kirwan's dilatations are too small. 



