5S HEAT OR CALORIC. 



(m.) Other points usually marked on the scale. Blood heat is? 

 marked 98 for the human subject ; fever heat 112 ; the mean sum- 

 mer heat of the day light in temperate climates,* 1 76 ; ether boils at 

 98; alcohol 176 J ; mercury 656 G ,f 



(n.) Other scales used in different countries. 



As the division of a thermometrical scale is entirely arbitrary, it 

 varies in different countries. In the thermometer of Reaumur freez- 

 ing water i& and boiling water 80, 



In Spain and Italy, this thermometer is still used ; but in France, 

 since the revolution, Reaumur's has been discarded, and that of Cel- 

 sius adopted, under the name of thermometre centigrade, in which 

 freezing water is G, and boiling water 100. To reduce the degrees 

 of Fahrenheit to those of the centigrade, substraet 32, then multiply 

 by 5 and divide the product by 9 y because each degree of Celsius 

 = f of lof Fahr. 



In converting the centigrade degrees into those of Fahrenheit y 

 double the centigrade number, subtract y 1 ^, then add the constant 

 number 32. Thus, 10 cent. X2=20- r V=20 -2 = 18 + 32= 50. 



To convert the degree of Fahrenheit into those of Reaumur, sub- 

 tract 32, multiply the remainder by 4 and divide the product by 9 : 

 or, the reverse, that is, multiply the Reaumur degree by 9, divide by 

 4 and add 32. { 



Mr. Murray proposed another division of the thermometrical scale ; 

 namely,, into one thousand degrees, counting from 39, the freezing 

 point of mercury, to 672, its supposed boiling point. The advantages 

 proposed, are a more minute division, the avoiding of negative 

 degreesand fractional parts, &,c.f 



Thermometrical scales are often compared, by drawing a diagram; 

 to exhibit them side by side, when any line drawn at right angles to 

 the scale will cut the correspondent degrees, which may thus be read 

 by inspection. 



In Russia, De Lisle's thermometer has been adopted ; in that y 

 freezing water is 150, and boiling water or melting snow is ; a very 

 awkward division. 



(0.) Principle of the graduation. 



This is founded upon the fact that the temperature of freezing 

 water and of melting snow or ice is the same, all the world over ; 

 and that pure water (the pressure of the atmosphere being the same} 

 boils every where at the same temperature. 



* Probably too high. f Murray's El. 6 ed. Vol. T. p. 103. 



\ Because the zero of Fahrenheit's thermometer is 32 lower than that of the cen- 

 tigrade or Reaumur. Before reduction, we must therefore subtract 32 from the 

 Fahrenheit degree, or add it to that of Reaumur, or the centigrade. 



See Murray, 2 ed. Vol. I. p. 139. 672 was then admitted as the boiling point 

 of mercury. For other modes of graduation, see Ferg. Lect. Vol. I, p. 181. an<H 

 Cavallo's Philos. Vol. Ill, pp. 19, 20. 



