520 Prof. R. Threlfall and Mr. J. F. Adair. On the 



MM 2 



dp 



Here T is the absolute temperature and J is Joule's equivalent. 

 The equation may be written — 



* = i , T . W 



Cp 1 1 d T v ' 



o Cp . — — 



v v dp 



in which i s the coefficient of expansion, and i.^lF with a 



v dT v dp 



negative sign is the isothermal compressibility, or the reciprocal of 

 the isothermal resilience. 

 c 1 



Thus — = mT -. 9 , if e denote the coefficient of expansion, and 



c v ^ _ TE e e 2 r 



Jcp.D 



D the density which is put for -. 



Thus it is requisite to know c^, the specific heat, besides the quan- 

 tities represented by the other letters. 



With a view to obtaining c p , it was discovered from Watts's 

 ' Dictionary of Chemistry,' vol. 5, p. 1017, that the composition of 

 Pacific Ocean water at a depth of 11 feet, Lat. 25° 11' S., Long. 

 93° 24' W., is— 



Na 10261-9 parts in 1,000,000. 



CI 189497 



S0 4 2786-4 



Mg 1315-1 



K 603-8 



Ca 471-9 



Br 310-2 



making the total solid content 3 "47 per cent, approximately. 



Again, in vol. 7, 2nd Supplement, p. 598, ifc is stated that a solution 

 NaCl+100H 2 O has a specific heat 0*962, with a specific gravity 

 1'0234; and this solution contains approximately 3'14 per cent, solid 

 matter. Thus, since c p occurs in a small term, it may be taken 

 without much error = 0*962. An experiment made by Mr. Flint, 

 one of the students in the Laboratory, gave a value practically the 

 same as the value here taken. 



The value of e has been previously found to be 0*000221. J is 

 taken 42 x 10 6 , and D the density given in the Table. 



