APPENDIX 377 



Liquids heavier Liquids lighter 



Hydrometer. than water. than water. 



Brix (Prussian) , 400 , _ 400 



at 12-5 B-. = 15-62 C. 400 - n 400 + n 



200 



Balling * , 



200 - n 200 + n 



Gay-Lussac, at 4 C. . d= 10 d = 10 



100 - n 100 + n 



Beck, at 12-5 C. d= 17 d = 17 



170 - n 170 + n 

 136 ' 8 



Cartier, at 12-5 C. d - d = 



126-1 - n 126-1 + n 



CONVERSION OF TEMPERATURES FROM ONE THERMOMETRIC SCALE 



TO ANOTHER. 



In this book all temperatures are stated in the Centigrade scale, 

 and it is to be regretted that the Fahrenheit thermometer is still 

 commonly employed in England. Though the relationship between 

 the two is comparatively simple, it is troublesome and confusing to 

 have two scales in use. It is perhaps hardly necessary to state here 

 that the interval of temperature between the melting point of ice and 

 the maximum condensing temperature of saturated aqueous vapour at 

 the normal pressure, is divided in the Centigrade scale into 100 equal 

 parts or degrees, in the Fahrenheit scale into 180 degrees, and that 

 the scale commences from the melting-point of ice in the former, but 

 from a point 32 below this temperature in the latter. Hence the 

 equations 



C. = |( F. - 32) 

 and F = | C. + 32. 



Though these formulae are simple enough and easily remembered, 

 when many conversions have to be made they are troublesome. A 

 graphical method of connecting the two has been found very conveni- 

 ent in practice, and the diagram on p. 378 will be useful, as it enables 

 a temperature expressed in either scale to be converted into the cor- 

 responding temperature in the other scale, without the trouble of in- 

 terpolation. The graduations extend from - 35 C. (- 31 F.) to 

 145 C. (293 F.) commencing in the lower left-hand corner and in- 

 creasing in all cases as i?he stem is ascended. 



