1818.] Wernerian Society 301 



also, that the horizontal shelves of Lochaber, and this vast crack 

 across the island, reflect a mutual light on each other, elucidat- 

 ing the history of both. 



March 16. — Mr. Leslie read an account of his new instrument, 

 called the sethrioscope. As a description of it is already in the 

 hands of the public, it is unnecessary to give any abstract of 

 the paper at present. 



At the same meeting Dr. Brewster laid before the Society a 

 paper " On a New Theory of Double Refraction." 



WERNERIAN SOCIETY. 



Dec. 20, 1817. — The Secretary read a communication from 

 Mr. Hood, surgeon, Kilmarnock, on some fossil tusks found in 

 the parish of Kilmaurs, in Ayrshire. 



In digging through a bed of alluvial clay to the depth of 17-i- 

 feet, four large tusks, resembling those of the elephant, were 

 found ; and also the rib of some large animal. The largest tusk 

 measured 40 inches in length and 12g- inches in circumference 

 at the maxillary extremity, and 84- inches at the end. In the 

 same bed of clay, remains of shells were found. 



At the meeting on Jan. 10, 1818, Prof. Jameson read a paper 

 on the geognostical characters of simple minerals. He remarked 

 that the distribution of plants and animals over the earth is deter- 

 mined by distance from the equator, height above the level of 

 the sea, kind of exposure, and other circumstances ; but that a 

 different arrangement is observable in mountain rocks, for they 

 are universally distributed, and the same species occurs equally 

 at the equator, and towards the poles, at the level of the sea, as 

 above the line of perpetual snow. Although the distribution of 

 mountain rocks is thus proved to be independent of climatic 

 influence, yet it would appear that the grand series of primitive, 

 transition, and floetz rocks have their peculiarities as to height 

 above the sea, to the spaces occupied by the different forma- 

 tions, and to the general direction, dip, and inclination of the 

 strata. Thus, although the general characters of the formations 

 to the north of the Frith of Forth agree with those of similar 

 groups of rocks on the continent of Europe, and although they 

 exhibit such characters as show that they are members of 

 the same general series, and have been formed at the same 

 time, yet if we contrast them with the collective, primitive, 

 transition, and floetz rocks of other tracts, as of Switzer- 

 land, for example, we shall find very striking differences, not 

 only as to the spaces occupied by the rocks, but also to their 

 relative heights above the sea, and the arrangements of their 

 direction, dip, inclination, &c. In short, such a comparison, 

 Professor Jameson remarked, would show that these two masses 

 of land, although exhibiting the same species of rocks and struc- 

 tures, yet are distinguished by particular and individual charac- 

 ters—that botli are to be viewed as portions of the earth's 

 surface formed from the same general fluid by a process of crvs- 



