168 



THE GEOLOGIST. 



magnesia, and potash, and the remaining iron changed to the per- 

 oxide state. The length of time required for the water to penetrate 

 apiece of trap I know not ; but that the soluble power of the water 

 is great, is evident, by placing a piece of such rock in distilled water ; 

 100 grains digested for six days, at summer heat, lost one per cent. : 

 the water had an alkaline reaction, and contained magnesia, potash, 

 and lime." Mr. Napier exhibited a specimen of a boulder, showing 

 " the powerful action constantly going on in the earth, changing the 

 character of rocks;" and he also remarks, that "the crust or outer 

 portion of stones of this soil have generally been looked upon as in- 

 crustations, from the water in which they have been placed having 

 salts in solution that have become deposited upon the stone or kernel 

 portion. Such incrustation does take place upon organic substances 

 placed in mineral waters; but in this instance, as in most other 

 minerals, the change has evidently been caused by the decomposition 

 of the original stone." 



Not far from the town of Lochwinnoch, on the road to Kilbarchan, 

 in which parish it is situated, stands one of the most remarkable 

 erratics in the west of Scotland. Mr. William Fulton, M.A., Govan, 

 first informed me of its existence, and last July both of us measured 

 it. The immense basalt fragment, judging from the direction of the 

 deep and broad scratches on its south-east side, appears to have been 

 carried along in two directions ; the force, 

 either ice or running water, thus causing 

 the marks or scratches to cross one another 

 almost at right angles. (See sketch.) The 

 stone is 11 feet in height and about 69 feet 

 in circumference, and appears to be two miles 

 west of the town of Kilbarchan. The stream 

 Fig. 8— Erratic block, Loch- called St. Bride's Burn is not very far from 

 wmnoch. the erratic, which receives the local name 



Clochodrickstone, said to be from the Gaelic, meaning the Druid's 

 stone. 



AN ATTEMPT TO CORRELATE THE GLACIAL AND 

 POST-GLACIAL DEPOSITS OP THE BRITISH ISLES, 

 AND TO DETERMINE THEIR ORDER OE SUCCES- 

 SION. 



By Professor William Kixg, 



Of the Queen's University, Ireland, and the Queen's College, Gal icay. 



The classification given in the sequel is based on the following pre- 

 mises : — 



1st. The entire area of the British Isles has undergone at different 

 times, during the Glacial and Post-Glacial periods, a succession of 

 secular elevating and subsiding movements. 



2nd. At the close of the Pliocene period, the relative level of land 



