, c. M:K\\TN .M:\KIN AND MR. D. R. PYE ON THE 



this curve for each of Series I. experiments are given in column S of Table VI., and 

 tli.- c,,rn-.-t-.l v.ilu.-s of L in the last column. These values of L were plotted ;m<l 

 values taken from the smooth curve are given in column 5 of Table IX. 



Fig. 9. 



If we proceed now to the construction of the true 6<j> diagram a further difficulty is 

 met with. If a constant-pressure curve is drawn as before, using the values of I 

 already obtained, the result is the curve KA. The difficulty is to draw the true 

 limit curve GA, which was previously assumed to coincide with KA. The authors 

 have been unable to devise any direct experiment to fix the position of the limit 

 curve relatively to the constant-pressure curve KA, and an indirect method had to 

 be used. The fundamental thermodynamic equations give the well-known equation* 



(**} - (**\ 

 \dpJ0 \dO/ P ' 



Let H, fig. 7, be the pointed.,; then 



HG = ** - r(i) * 



Jpi \O,u,ip 



Thus the distance fy between the limit curve and the constant-pressure curve can 

 * Cy. PMSTON'S -Theory of Heat, 1 p. 740, 2nd edition. 



