104 



required volume. The method of Figure III for the Law of 

 Charles may be combined with either of the methods for the Law 

 of Boyle, Figures I and IV. 



Figures V and VI show how this can be done. Each is 

 arranged to give a solution to the same definite problem, viz., "To 

 find the volume at N.T.P. of a mass of gas which at 72 cm. and 

 35 0 c. occupies 1,000 cubic centimetres." 



Figure V. — Take OA, OB, OC to represent 100 c.c, 

 (273 + 35) 0 , and 273 0 , respectively. From C draw CD parallel to 

 BA. Take OE, EF to represent pressures of 72 cms. and 76 cms. 

 respectively. Through D draw a vertical and through E a hori- 

 zontal line and let them meet in P. Join FP and produce it to 

 meet OA produced in the point X. Then DX represents the volume 

 corrected for both temperature and pressure. 



Figure VI. — Take OA, OB, OC to represent 100 c.c, 

 (273 4- 15 )°, and 273 0 respectively. Through C draw CD parallel 

 to BA. Then OD represents the volume corrected for temperature 

 only. Take OE, OF to represent pressures of 72 and 76 cms. 

 respectively. Join DF and through E draw EX parallel to FD, 

 cutting OA in X. Then OX represents the volume corrected for 

 both temperature and pressure. 



N.B. — The accompanying figures are reductions of those shown 

 when the paper was read. The scales specified are those of the original 

 diagrams. 



