1821.] Causes of Calorific Capacity, Latent Heat, $$c. 51 



the corresponding elasticities of a given volume of any kind of 

 gas, or the corresponding volumes under a given pressure. The 

 principal table is divided into four columns. In the first, 1 have 

 given some miscellaneous observations, extracted chiefly from 

 Murray's System of Chemistry, fourth edition, and Humbolt on 

 Isothermal Lines, and arranged according to the degrees of 

 Fahrenheit. Generally, however, 1 have not thought it neces- 

 sary to interpolate the table so as to make the observations stand 

 against the precise degree of Fahrenheit at which they have 

 been made ; but have considered it sufficient to place them 

 against the nearest degree. 



In the second column, 1 have given the degrees of tempera- 

 ture agreeably to my theory, from the beginning of the scale up 

 to 3000. These numbers are those to which all the others are 

 adapted. For the first 800, they are set down to every 10 degrees. 

 From this point, which is 200 of our degrees below freezing, up 

 to 1030, nearly 100° above the point of boiling mercury, the 

 numbers proceed by single units, and afterwards by tens. 



The third column contains numbers which show the expansive 

 force of a given portion of gas under an invariable volume, the 

 temperature being the same as that in the second column ; or it 

 shows the volume that a given portion of gas would assume at 

 the temperature of the second column, supposing its elasticity to 

 continue invariably the same. These numbers are only the 

 squares of the numbers of the second column, with three of the 

 right hand figures cut off for decimals. By this arrangement, 

 we have 1000 in" each column at the term of melting ice, which 

 is a point the least, perhaps, of any other in the whole scale of 

 temperature affected by external causes ; and which, therefore, 

 appeared to me to be the fittest for being the unity of the scale. 

 By putting the term of melting ice 1000, we also assimilate this 

 scale of temperature as nearly, perhaps, as convenience will allow 

 us, to the scales more commonly in use ; for supposing the elastic 

 forces or the volumes of gas at the extreme temperatures of the 

 fluidity of water to be as 8 to 11, there will be 1724-ths of these 

 degrees of temperature to correspond with 180 of Fahrenheit's, 

 which, with respect to extent, have been found to be very con- 

 venient in practice. 



Another advantage seems to arise from this construction of 

 these columns, which is, that if future observations should give 

 a ratio in the volumes or elasticities of a given portion of gas, at 

 the temperatures of water freezing and boiling, different from 

 that of 8 to 11, there will be no necessity for making any differ- 

 ence in the arrangement or relation of these two columns ; it 

 will be only to put the boiling point a little higher or lower, as 

 experiments may direct. 



The fourth column is the temperature of the air thermometer, 

 according to Fahrenheit, adapted to the expansion of air in the 



e2 



