446 Chemical Notices : — Preyer on the Colouring -matter of Blood. 



a very large number indeed, <p becomes a very large quantity 

 for points of the surface at which u is greater than 1, and a very 

 small quantity for points where u is less than 1. But <£ is in- 

 dependent of u. The only way of avoiding these contradictory 

 results is to make u = l ; that is, the sphere is the only surface 

 which satisfies the problem. 



Reverting now to an earlier form of the condition, putting 

 u = l, and 



p'=VoVi+ •<•+/>'''+••• 

 a series of Laplace's functions, it becomes 



I t i p'i P, v^ dfi dec dv, or ^fj 4 p\ zf + 2 dv } = 



for all positive integral values of i. Hence 



p|=0; or /9! = 0, p 2 = 0, ...-, 



and p is not a function of \i and co, but only of the distance from 

 the centre. Hence the only surface which satisfies the problem 

 is the sphere, and the density of its mass is a function only of 

 the distance from the centre. 



J. H. Pratt. 

 Allahabud, March 23, 1867. 



P.S. — Such of your readers as will revert to my first papers 

 on the fluid theory of the earth, will see the very important 

 bearing of this proposition; for it leads to this result — that if 

 the surface of the earth be a spheroid of equilibrium, the ar- 

 rangement of its mass, whatever its past history, must now un- 

 doubtedly be according to the fluid-law. 



LVII. Chemical Notices from Foreign Journals. 

 By E. Atkinson, Ph.D., F.C.S. 



[Continued from p. 207.] 



"DREYER has described a method of determining the amount of 

 ■*■ colouring-matter in the blood by means of the spectrum*. But 

 few experiments have been made with a view of determining the 

 quantity of haBinoglobine (hsematocrystalline) in the blood, doubt- 

 less owing to the want of an accurate and convenient method. 

 The determination has been made either by incinerating the 

 blood and determining the amount of iron in the ash by volu- 

 metric analysis, or by determining the intensity of the colour of 

 blood after a known dilution with water. Preyer points out at 



* Liebig's Annalen, November 1866. 



