1814.] }Pcrnerian SocieiTj. S05 



nexion with others stated by Mr. Jameson, illustrates the che- 

 mical nature of sandstone. The slate-chiy presents a curious con- 

 nexion with felspar, — an appearance in favour of the chemical 

 nature of slate-clay, and of the connexion of slate-clay as a mem- 

 ber of the felspar series. In tiie limestone strata are situated the 

 well-known lime quarries of Dalgctty. The trap rocks contain 

 veins of trap ; also of sandstone, limestone, and slate-clay, and 

 portions of slate-clay and limestone resembling fragments : all of 

 which appearances Professor Jameson considers as chemical co- 

 temporaneous formations ; and he concluded by remarking that 

 probably tlie prevalent theory of the mechanical formation of floetz 

 rocks would l)e found to be less consonant to nature than the hypo- 

 thesis of their chemical formation now proposed. 



At the meeting 1 2th February, Dr. Macknight read a paper on 

 the Cartlane Craig : a vast chasni in sandstone rocks above Lanark, 

 formed by the lower part or projecting shoulder of a great moun- 

 tain-mass, detached from the body or iipper part, and extending 

 more than three quarters of a mile in a curved line from S. W. 

 to N. E., whh a depth of several hundred feet. To ascertain how 

 this enonuous and striking fissure has been produced is a curious 

 geological problem ; the more interesting, that the phenomena^ of 

 the Cartlane Craig are such as to furnish a remarkable test for trying 

 the merits of the two theories which now divide the geological 

 world. According to the principles of the igneous theory, a vein 

 of trap, which travel ses the strata in a direction almost perpendi- 

 cular to the course of the ch'asm near its centre, renders it ah ex- 

 ample on a great scale of disruption and dislocation by explosion 

 from beluw. On the other hand, the Cartlane Craig evidently 

 possesses all the data requisite to form a case of what is called in the 

 aqueous theory, suhs'ideuce : an explanation which Dr. Macknight 

 is inclined to prefer, because the trap, from the smallness of its 

 mass, seems totally inadequate, as a mechanical power, to the 

 effect produced : because the direction of the rent, instead ot fol- 

 lowing the course of the vein, which it must have done had it 

 owed its existence to this cause, is very nearly at right angles to 

 that course ; and because it ai)pears on examination that the trap 

 Itself had been originally a part of the formation or mountain mass, 

 previous to the time when the rent took place'. — The Cartlane sand- 

 stone l)elongs to the (»Ulest of the floetz rocks. In the under part 

 of this formation, it alternates with grey-wacke, and contains lime 

 in calc-spar veins. Some varieties are grtod specimens of what Mr. 

 Jameson considers as chemical depositions. The trap consists of 

 compact greenstone; basalt including olivin and augit j and a sub- 

 stance intermediate between basalt and clinkstone. 



At the sume meetiMg, the secretary read a communication from 

 Dr. Thomson, containing a descrijition and analysis ot a specinieii 

 of lead ore from India. It appeared to be a chemical combination 

 uf the sulphureis of lead, copper, and iron, in the following pro- 

 portions : 



^^ IV. VuL. III. U 



