303 Minerals from Greenland. [Feb. 



gravity; namely, 5*7604 at 60^ of Fahrenheit; and was 

 finally confirmed by Dr. Wollaston, who found it to be yttro- 

 tantalite, nearly pure. Besides this variety, i found a crys- 

 tallized substance, which I believe to belong to the same ; it 

 occurs in minute regular octohedroos, imbedded in felspar: 

 their fracture is conchoidal ; lustre, somewhat metallic ; and 

 colour, bright orange brown. These external characters first 

 induced me to consider this misic ral as a variety of spinel ; but 

 I have changed this opinion, in consequence of an investiga- 

 tion of Dr. Wollaston on some small atoms I was enabled to 

 detach, who informed me that yttria entered into its compo- 

 sition ; but that the portion submitted to analysis was too 

 small to complete the experiment. There was only one very 

 small specimen in the collection ; and so little attractive is its 

 appearance, that it was upwards or four years in my possession 

 before I examined it. The form of the crystals first attracted 

 my attention ; but they are so minute, and so thinly scattered 

 in the matrix, that the whole would scarcely have sufficed for 

 the subject of an analysis, minute as the portions are which 

 are now required for that purpose. 



Allanite, 



The last metallic substance I have to mention is that which 

 was mistaken by myself for gadolinite, and subsequently found 

 to be an unknown compound by Dr. Thomson, to whose polite- 

 ness I am indebted for the compliment paid me, of giving it to 

 the world under the name of alianite; although, perhaps, the 

 chemical appellation of brown oxide of cerium would have been 

 fully as appropriate. I have now nothing to add to the descrip- 

 tion already published by Dr. Thomson, excepting that the same 

 substance has been found among a parcel of minerals from the 

 Mysore, yielding by analysis the same notable proportions. It 

 is somewhat singular that a new fossil should be discovered, so 

 nearly at the same time, among minerals from two quarters of 

 the world so widely separated. 



Aggregate Rocks, 



1 have before mentioned that the greatest part of this collec- 

 tion consisted of stones destitute of any interest : my present 

 object is merely to mention a few of the most characteristic. 

 Of granite there were several varieties ; but the most singular 

 was a compound of felspar and quartz, like the graphic granite; 

 but in this the base was of a bluish grey colour, and the 

 included crystals pure white. Porphyr?/, of a base of a dark 

 brown compact felspar, containing sharp angled crystals of the 

 same, o.f a light flesh colour; also a variety similar to the red 

 compact felspar porphyry of the Pentland hills. Greenstone, of 



