EETIEWS. 
39 
For those who want to get a fair running knowledge of geology with the 
least amount of trouble, Mr. Jukes's book will be just the thing. We 
think highly of Mr. Jukes's abiUty, and we wish it had been a great work, 
or a small work on some special topic, — something, in short, beyond an ele- 
mentary treatise going all over the old ground, — that we might hare spoken 
as much kind praise as we have every pre-existing desire to give to any 
meritorious labours that emanate from any of the Survey men. 
The Flora of Marlhoroiigh. By T. H. Preston. 
With Mr. Preston's brochure as a Flora we may have, seemingly, little 
to do, but there is an important connection between the plants of a district 
and the soil on which they grow. This soil may not be necessarily the 
debris or the resultant of the weathering and atmospheric degradation of the 
true geological strata of the district, and indeed it may be, as it very often 
is, formed from a superficial covering of the drifted and over-covering 
materials of a later and long subsequent age to that of the underlying 
rocks to which the main outlines of the physical geography are "due. 
Botanists have perceived this relationship, and although they must neces- 
sarily regard it in a diflerent light, we find that in local, and even in 
general Floras, considerable attention is now paid to the geological features 
of the district or country under botanical description. In this manner 
the geology of Marlborough is set before us in the little volume we are 
1 reviewing, before even the flowers of the region are recorded. This survey 
I of the botanist is especially useful in its way to the practical geologist, 
I because it investigates the superficial covering of the earth in a manner in 
which he would be little likely to do, and yet not the less important, as by 
it we obtain a knowledge of the workings of external agencies upon the 
ground tliat produces vegetation. In the neighbourhood of Marlborough, 
we are told that the surface for miles round, and to a great depth, has been 
entirely formed by these external agencies ; the Kennct, as an example, we 
are told, has at Lockeridge, only four miles from its source, filled up one 
of its former courses, and made a new track for itself through the marshy 
ground. On the northern side of the Kennet, the country consists almost 
entirely of Upper Chalk, with a few outlying patclies of red clay on the 
tops of the hills. In a wood to the north of Mildenhall, there occurs a 
red stratified clay, more than twelve feet in thickness. About four miles 
east of Marlborough, on the ridge by the Kennet, there is a vertical fault 
running nearly north and south ; the western side being occupied by hori- 
zontal layers of Upper Chalk Avitli flints, and the eastern by a reddish- 
brown sand, containing flint pebbles up to a pound in weight. Between 
Graham Hill and Martinsell the chalk is stated to be covered by boulder- 
clay, which is said also to extend westward as far as Clatford Bottom, and 
probably to form the subsod of the greater part of the west woods, and on 
the eastward runs into Savernake Forest. In the valley to the south of 
Granham Hill there is a strip of light-coloured sandy clay overlying the 
chalk, and to the south of this what is called " a mottled red boulder-clay," 
containing large masses of flint-nodules and sandstone boulders. JXear the 
top of the chalk slope at the north-west corner of the forest there is a 
trough-like hollow in the chalk, five-and-twenty feet wide and eight feet deep, 
fitted up with layers of red clay with large broken flints and chalk rubble, 
and thickly studded with " two kinds of fossil shells of the genus Helix, 
which very much resemble occlusa, and a smaller species, II. Urhani, 
some of which are beautifully marked. This hollow may have been the 
