80(5 Trench National Institute. 



Strontian and Ben Nevis, l^lie rocks which compoje the 

 districts of Strontian are mica slate, gni.-iss, and granite ; 

 and the lead-glance, which occurs in gneiss, is associated 

 with iron pyrites, cross-stone, calc-spar, foliated zeolite, 

 strontian, and heavy spar. Ben Nevis is an overlying 

 massive formation, which rests on gneiss and mica-slate, 

 approaching in some places to clay- slate. In this forma- 

 tion compact feldspar is the leading ingredient. The infe- 

 rior mass consists of sienite, passing from the sin)ple gra- 

 nular to the granular porphvritic ; and the npper portion of 

 the mountain, comprehending the summit, with about I'JOO 

 feet of the perpendicular hv'ight below it, is composed of a 

 dark-coloured rock, which, for the most part, is porphy- 

 ritic, and seems to be intimately allied in its characters to 

 compact feldspar. This appears from tlie gradual transition 

 of the one substance into the other, which is distinctly ob- 

 served under the tren>endous precipice of Ben Nevis to the 

 NE. and demonstrates the identity and continuity of the 

 whole formation. The colouring matter appears to be 

 hornblende intimately mixed with the substance of th^ 

 rock. At first view, the whole mass might be considered 

 as a formation of clinkstone and porphyry-slate. But a 

 more minute investigation discovers many oryctognostie 

 characters of distinction from these substances, which are. 

 less crystalline, and belong to a more recent sera of forma- 

 tion . 



At the same meeting, Df. Arthur Edmonstone read an 

 account of the peculiarities of the Zetland sheep; with re- 

 marks on their diseases. And the secretary read a commu- 

 nication from lieutenant-colonel Imrie, describing a vein 

 pf greenstone, which occurs in Glencoe, and which appears 

 to have been overlooked in the mineralogical descriptions of 

 that district. 



FRl'NCH NATIONAL INST^TUT^. 



Analysis of the Lahours of the Class of Mathematical and 

 Physical Sciences of the French Institute^ for the Year 



All the sciences which are founded upon facts have this 

 distinguished advantage, namely, that every experiment 

 and every observation contribute to their progress. Indeed^ 

 properly speaking, there are no discoveries made in vain, 

 80 far as the physical sciences are concerned. Whatever 



• Translated from the original, distributed at the public sitting of the 

 jlass, 2d Jan. 1310. 



may 



