H E A 



210 



212 



, 232 



~, 222 



r~~ 220 



316 



~~ 240 



~~ COO 



640 

 *~* 656 



TABLE IV. 



Boiling temperature of water. 



Heiglit of the boiling point in Fahrenheit? s Thermometer at different 

 heights of the Barometer. 



Barom. Ht. of boiling point. 



10.0 2J30.571 



30. 5 212- 79 



30- 212. 00 



29. 5 211. 20 



29. 210. 38 



28. 5 209. 55 



28. 208. 69 



27. 5 207. 84 



27. 206. 96. 



And in general Dr Horsley's rule dedu- 

 ced from De Luc is, height = -^ ~ 



8990000 



log. #. 92.804, where z height of Baro- 

 meter in lOths of an inch. 



In an exhausted receiver water boils at 

 98. or looo. in Papin's digester at 412<>. 



From tliis variation in the height of the boiling point, arising from the 

 variation of the pressure of the atmosphere, an ingenious instrument 

 called the Therm ometrical Barometer has been invented by Mr Wol- 

 laston, for ascertaining the heights of mountains ; it appearing from 

 General Roy's experiments, that a difference of 1. in the boiling point 

 corresponds to 535 feet in height. Let .*. n difference of boiling points 

 at the bottom and top of a mountain, then 1 \ no I*. 535 feet I n X 535 

 = approximate height. To correct it for the temperature of the air, let 

 m mean temperature of the top and bottom, ascertained by a common 

 thermometer, then (see Barometer) n, 535 X (1 + m ~ 38 X .00244) 

 correct height.- (Phil. Trans.) 



TABLE V. 



Linear expansion of solids by heat. 



Dimensions which, a bar takes at 212 whose length at 32 if 1.000000.-^. 

 (Urej 



Glass tube ^ Smeaton 1.00083333 



Do. ~~ .^^ ^^^ Roy ~~ *~** 1.00077615 

 Deal *** .^, r^, Roy, as glass 



