168 
THE GEOLOGIST. 
magnesia, and potash, and tlie remaining iron changed to the per- 
oxide state. The length of time required for the water to penetrate 
a piece 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 ia the west of Scotland. Mr. William Fulton, M.A., Grovan, 
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, Locii- called St. Bride's Burn is not very far from 
winnoch. the erratic, which receives the local name 
Clochodrickstone, said to be from the Gaelic, meaning the Druid's 
stone. 
AN ATTEMPT TO COEEELATE THE GLACIAL AND 
POST-GLACIAL DEPOSITS OF THE BEITISH ISLES, 
AND TO DETEEMINE THEIE OEDEE OF SUCCES- 
SION. 
Br Peofessoe AVilliam Ki>'o, 
Oftlie Queen's University^ Ireland, and the Queen's College, Gahcay. 
The classification given in the sequel is based on the following pre- 
mises : — 
1st. The entire area of the British Isles has undergone at diff'erent 
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 
