Prof. Clausius on the Mechanical Theory of Heat, 427 



calculation of T.y also is attended with no further difficulty, 

 because T is determined from the simple equation 



T=273 4-^. 



I have collected the values of ^ and T .^ and given them in a 

 Table at the end of this memoir. For the sake of completeness, 

 I have also added the corresponding values of p ; those above 

 100° being calculated by Regnault, those below by Moritz. To 

 each of these three series of numbers are attached the differences 

 between every two successive" numbers ; so that from the Table 

 the values of the three magnitudes can be found for every tem- 

 perature ; and conversely, for any given value of one of the three 

 magnitudes the corresponding temperature can be seen. 



After what was before said of the calculation of g, it need 

 scarcely be mentioned that the numbers of this table are not to 

 be considered as exact, they being only communicated in the 

 absence of better ones. As, however, the calculations with refer- 

 ence to steam-engines are always based upon rather uncertain 

 data, the numbers can without hesitation be used for this pur- 

 pose, there being no fear that the uncertainty of the result will 

 be much increased thereby. 



As to the method of application, however, another remark is 

 still necessary. In the equations (XVII), it is assumed that the 

 pressure p and its differential coefficient g are expressed in kilo- 

 grammes to a square metre ; whereas in the table the same unit 

 of pressure, a millimetre of mercury, is retained as that referred 

 to in Regnault's tension series. In order, notwithstanding this, 

 to be able to apply the table, it is only necessary to divide every 

 term in those equations, which does not contain either p or q as 

 factor, by the number 13*596. This number, which is nothing 

 more than the specific gravity of mercury at 0° C, compared 

 with water at its maximum density, will for the sake of brevity 

 be represented by k. 



This change of the formulae, however, scarcely increases the 

 calculation, inasmuch as it is equivalent to substituting every- 

 where, in place of the constant factor y , — which, according to 

 Joule, has the value 423*55 already mentioned, — the other con- 



Btant, J__i:?3^_31.1505. (4,e) 



Ak-JSWQ-^^^^^^' .... I4b} 



W 



when, instead of the work W, the magnitude -y- will be found 



K 



in the first instance, and will subsequently merely have to be 

 multiplied hy k. 



47. Let us now return to the equations (XVII), and consider 

 first the second of them. 



2F2 



