4$ tiXPERIMENTS ON ALLAN ITE. 



Count Bournon, added to some experiments made by Dr. 

 Wollaston, he was induced to give the description, which 

 has since been published in a preceding part of the present 

 volume. 



About a year ago, Mr. Allan, who has greatly distin- 

 guished himself by his ardent zeal for the progress of mi- 

 neralogy in all its branches, favoured me with some speci- 

 mens of this curious mineral, and requested me to examine 

 its composition ; a request which I agreed to with pleasure, 

 because I expected to obtain from it a quantity of y//na, an 

 earth which I had been long anxious to examine, but had not 

 been able to procure a sufficient quantity of the Swedish 

 gadolinite for my purpose. The object of this paper is to 

 communicate the result of my experiments to the Royal 

 Spciety; experiments which cannot appear with such pro- 

 priety any where hs in their transactions, as they already 

 contain a paper by Mr, Allan on the mineral in question. 

 De«cnptioa of Sect. 1. I am fortunately enabled to give a fuller and 

 more accurate description of this mineral than that which 

 formerly appeared, Mr. Allan having since that time dis- 

 covered an additional quantity of it, among which he not 

 only found fresher and better characterised fragments, but 

 also some entire crystals. In its composition it approaches 

 most nearly to cerite; but it differs from it so much in its 

 external characters, that it must be considered as a distinct 

 species. X i^ave therefore taken the liberty to give it the 

 name of Allanite, in honour of Mr. Allan, to whom we are 

 in reality indebted for the discovery of its peculiar nature. 



Allanite occurs massive and disseminated, in irregular 

 masses, mixed with black mica and felspar ; also crystallised ; 

 the varieties observed are, 



1. A four-sided oblique prism, measuring 117* and 63*. 



2. A six-sided prism, acuminated with pyramids of four 

 udes, set on the two adjoining opposite planes. These last 

 are so minute as to be ijicapable of measurement. But, as 

 nearly us the eye can dtterinine, the form resembles fig, 1, 

 PI. H; the prism of which has two right angles, and four 

 measuring 135''. 



3. A flat prism, with the acute angle of 63° replaced by 

 ODeplane^ and terminated by an acumination, having three 



principal 



