Reviews: Ramsay—Geology of Great Britain. 63 
necessarily connected with fracture, he goes on tacitly assuming 
that rivers always make their own channels. The style of demon- 
stration is peculiar. Referring to the Vale of Reading, he asks: 
‘How did the Thames find its way through what was once that great 
unbroken scarped barrier of Chalk now called the Chiltern Hills ?’ 
The answer is grand: ‘Such phenomena are not confined to this 
river alone—zé is a trick that rivers have.’ 
The great River Niagara has, it is true, cut its way back unaided 
by any apparent fissure, like the miniature Chines of the Isle of 
Wight. But it has been demonstrated that the Wealden area could 
not have been raised to such an elevation as it has without producing 
fissures in the very situations now occupied by the river-channels; 
and, although these fissures may have borne no proportion to the 
wide, winding valleys that now intersect the downs, it is satisfactory 
to know that we have in them a directing cause. 
The marvels effected by atmospheric agencies are not less remark- 
able than those of rivers and glaciers. The geologist may now 
remove any amount of limestone by means of sour peat-water—as 
Hannibal dissolved the Alps with vinegar. But we need go no 
farther than our own Chalk Downs to see the action of rain on a 
stratum of easy solubility. The ‘ swallow-holes’ have been a fer- 
tile subject for contradictory speculation; and wherever the surface 
of the Chalk has been covered only by loam and gravel, itis furrowed 
‘and eroded. The fantastic outlines of the Chalk seen in some of 
the railway-banks near London could never have been exposed to 
the action of the sea, but have rather been formed, since the depo- 
sition of the brickearth over them, by the silent infiltration of rain- 
water dissolving the carbonate of lime and carrying it away laterally, 
and leaving the iron-stained siliceous residue. 
When speaking of the use of decomposed granite in the manu- 
facture of porcelain, Mr. Ramsay asserts that he has seen granite 
‘which had never been disturbed by the hand of man, that for a 
depth of twenty feet or more might be easily dug out with a shovel.’ 
A fact like this speaks as emphatically for the long exposure of our 
Cornish moors as any evidence derived from the succession of 
organic life can prove the lapse of time while the Secondary rocks 
were forming. The aspect of high antiquity presented by the 
Scottish Mountains is explained by the statement of the Lecturer, 
that the carving-out of those peaks and ridges, cliffs and valleys, com- 
menced before the time of ‘that extremely venerable formation, the 
Old Red Sandstone.’ 
We are obliged to pass over Mr. Ramsay’s views on the relations 
of the Stratified and the Igneous rocks, and the origin of Metamor- 
phism. But we will mention that in an early page he gives the 
weight of his authority for the observation that there are vesicular 
lavas of Carboniferous age; thus dispelling the silly and improbable 
speculation that sub-aérial volcanoes had no existence until the 
Tertiary age. 
In the lecture on mining, Mr. Ramsay gives a wholesome caution 
to those who are desirous of embarking in such speculations. The 
