1815.] IVernerlan Natural History Society. 13§ 



trituration in water; but I do not think that Mr. Jameson has been 

 quite so fortunate in his name as in the idea itself. All rocks, 

 which are still in the original state in which they were deposited, 

 he calls chemical deposites ; while he distinguishes those which have 

 been in the state of sand, or fragments, and afterwards ceffiented 

 together, by the name of mechamcal deposites. Now a chemical 

 combination means substances united together by chemical affinity ; 

 and one of the characteristics of this kind of combination is, that 

 the constituents enter always in the same proportion. 1 am afraid, 

 that according to this definition, very few rocks would be entitled 

 to the name of chemical deposites, while some of those that Mr. 

 Jameson would distinguish by the name of mechanical, (as shell 

 lime-stone,) would be in reality entitled to the name of chemical. 

 Some other phrase, {immediate deposites, for example,) might easily 

 be chosen to denote the idea, which then, in my opinion, would be 

 unexceptionable. 



The floetz rocks, which constitute by far the greatest portion of 

 ;he Pentlands, are conglomerate, sand-stone, clink-stone, clink- 

 stone porphyry, amygdaloidal clink-stone porphyry, green-stone, 

 compact felspar, clay-stone, clay-stone tuff, and porphyry. 



The conglomerate rock is composed of portions of quartz, grey- 

 wacke, grey-wacke slate, porphyry, felspar, flinty-slate, common 

 jasper, horn-stone, and mica. Two varieties of it occur, a hard 

 and a soft. It lies low in the hills, and Mr. Jameson supposes that 

 it alternates with grey-wacke. The sand-stone covers, and pro- 

 bably alternates with the conglomerate. Mr. Jameson considers it 

 as an immediate deposite. The clink-stone seems to be over and 

 alternate with the sand-stone. It often contains crystals of felspar, 

 and is then called clink-stone porphyry, or porphyry -slate. It 

 passes into compact felspar. The green-stone is an uncommon 

 rock in the Pentlands ; but the compact felspar occurs in great 

 abundance. It passes into clay-stone, which is a very copious rock, 

 and often constitutes the summit of the different mountains. The 

 porphyry, which is merely clay-stone containing crystals of felspar, 

 often covers it. 



14. On conglomerated or hrecciated Bocks, By Professor Jame- 

 son. In this paper, Mr. Jameson endeavours to show, that many 

 rocks hitherto supposed to be composed of fragments of older rocks 

 cemented together, are in fact immediate, or, as he calls them, 

 chemical, deposites from a liquid. The idea certainly deserves to 

 be carefully examined. I have little doubt that, to a certain extent 

 at least, iiis notions will be found correct ; but it is difficult to 

 reason on such a subject in a satisfactory manner, because the evi- 

 dence can only be derived from an ocular inspection of the rocks 

 ill question. Conglomerated rocks occur in prin)itive, transitiun, 

 and flociy. format ions. To the fust belong conglomerated gneiss, 

 conglomerated mica-slate, conglomerated granite, and conglo- 

 ineniied lime-stone. All of these Mr. Jameson considers as innne- 

 diate deposites i because the supposed fragments pass insensibly 



