]52 Scientific Intelligence. [Feb. 



possessed for examination, prevents any more accurate detail of its 

 composition. 



" It is found imbedded in the amygdaloids of the cliffs of Scurr more, 

 the base being either a basalt, or a black indurated claystone. The 

 nodules are generally round, and vary from the size of a radish seed 

 to that of a pea or upwards. Occasionally they are oblong and com- 

 pressed, and sometimes scale off in concentric crusts. In a few in- 

 stances they are hollow within, the interior surface having a blistered 

 aspect ; or else the cavity of the amygdaloid is covered with the sub- 

 stance in a form resembling that of an exudation. More rarely still 

 the nodule is compounded, containing a spherule of calcareous spar 

 within an investing crust of the mineral. When long exposed to the 

 air, it decomposes in the form of a rusty powder, which is thus occa- 

 sionally found filling those cavities that are visible on the surface of 

 the fragments in which it is found. The variety from Fife differs from 

 that of Rum, in being less regular in form, and less frequently round, 

 while it is commonly also of a larger size. From the most characte- 

 ristic quality of this mineral, the term chlorophseite may be conve- 

 niently adopted for distinguishing it." Dr. Macculloch adds, that he 

 has since seen this mineral brought from Iceland by Major Peterson. 

 (Western Islands, vol. i. p. 504.) 



" In reviewing some of the amygdaloids collected in Mull, I disco- 

 vered a non-descript substance intermixed with some prehnite, but too 

 small in quantity for examination. Having since found the same mi- 

 neral in greater abundance in Glen Farg, I shall give the best descrip- 

 tion of it I am enabled to do from these specimens, as I cannot now 

 assign the exact locality of the former. It has hitherto escaped the 

 observation of mineralogists, and the description, however imperfect, 

 will therefore be of use, by directing their attention towards it, and 

 thus probably ascertaining its existence in other places. Its external 

 characters are very limited, since it consists of a loose white powder, 

 somewhat coarser than silica as it is obtained from the silicated alka- 

 lies, gritty between the teeth, but not so hard as to scratch, glass. 



" It does not effervesce with acids, and before the blow-pipe it 

 melts immediately into a transparent colourless bead, with apparently 

 the same facility as glass. It is certainly at least more fusible than 

 datholite. I have not been able, from its condition, to determine its 

 specific gravity. On attempting to analyze the very minute quantity 

 that could be spared for that purpose, it was found to consist princi- 

 pally of silica. A small quantity of lime was taken up by muriatic 

 acid, but its fusibility was not destroyed by that treatment. When 

 treated, however, in a similar manner by sulphuric acid, the fusibility 

 was destroyed. No alkali was found in it, nor any boracic acid, nor 

 any ti'aces of metallic matter. It is not easy therefore to account for 

 its great fusibility, unless it should contain the new alkali. In this 

 ^uncertain state must its chemical composition remain, until other spe- 

 cimens are procured to admit of a repetition of these experiments on 

 a more extensive scale. It is found filling irregular cavities in the 

 amj-'gdaloid of the valley above-mentioned, so well known to mineral- 

 ogists ; where it is accompanied by analcime, mesotypc, prehnite and 

 calcsreous spar. There is no appearance of decomposition in the 



