336 Intelligence and Miscellaneous Articles. 



cations to account for on the theory of undulations. But it 

 is evident that what Prof. Challis means by aberration, is the 

 circumstance that s x is displaced from s 2 through the angle 

 which I have mentioned. Prof. Challis's reasoning, by his 

 own confession, does not explain aberration in the sense in 

 which I used the word ; for he says that it follows from ob- 

 servation (not theory alone), that s 2 coincides with s. 



LI II. Intelligence and Miscellaneous Articles. 



ANALYSIS OF DIASPORE FROM SIBERIA. 

 BY M. A. DAMOUR. 



r r , HE remarkable characters of diaspore have frequently attracted 

 ■*• the attention of mineralogists, and have been extremely well de- 

 scribed and analysed by MM. Children, Dufrenoy, and Hess. The 

 author observes, that he should therefore have abstained from re- 

 ferring to them, if he had not had occasion lately to observe a sin- 

 gular property of this mineral which had not been previously noticed. 

 The diaspore is a well-known hydrate of alumina. It is shown by 

 the experiments of M. Dufrenoy, that tbis mineral, even when long 

 boiled in sulphuric acid, not only resists its action, but retains all its 

 water. M. Damour, on repeating this experiment, obtained the 

 same result ; but he afterwards found that the diaspore, when de- 

 prived of its water by calcination, was almost totally soluble in sul- 

 phuric acid when assisted by heat. 



This property is the inverse of that which chemists always ob- 

 serve with respect to hydrates, and in general with respect to sub- 

 stances which have not been calcined. In fact, the greater number 

 of these substances lose their solubility in acids after they have been 

 heated to redness. In this case the contrary occurs : the peculiar 

 molecular condition of the crystallized hydrate of alumina, consti- 

 tuting the diaspore, appears then to be the only obstacle to the na- 

 tural affinity of this hydrate for the sulphuric acid ; for calcination, 

 by destroying this arrangement of the molecules, restores the usual 

 properties of alumina. 



M. Damour took advantage of this circumstance in order to sim- 

 plify the method of analysing diaspore. 



The mineral was first purified by digesting it, reduced to very fine 

 powder in dilute hydrochloric acid at a moderate heat. There was 

 dissolved a notable quantity of oxide of iron accidentally mixed with 

 it. The powder, after washing, was perfectly white. The propor- 

 tion of water was found to be nearly similar in three different ope- 

 rations : to determine this the dried powder of the mineral was suf- 

 fered to remain under a receiver over a stratum of pumice moistened 

 with sulphuric acid, this powder was weighed and placed in a small 

 covered platina crucible : in order to prevent the projection of the 

 powdered mineral, the crucible was placed in another of the same 

 metal ; the whole being weighed, the crucibles were submitted to 



