SFuly 13, 1871 | 
NATURE 
199 

waters of the Tamina.” The only points in Prof. Tyndall’s 
description to which wea little demur are when he speaks 
of the traveller “ passing along the chasm midway between 
top and bottom,” the fact being that the well-known 
gallery is only a few yards above the Tamina ; and where 
he quotes the gorge as an illustration of water-action upon 
limestone rock. It is true that the strata here are not 
crystalline, and they may be occasionally calcareous, but 
we should hardly venture to apply the name of limestone 
to the hard black shales or slates out of which the gorge 
itself is cut. Professor Tyndall also omits to call atten- 
tion to the close connection between the direction of the 
principal joints and the form of the gorge. This 
is especially noteworthy at Pfaffers, where the chasm 
is not vertical, but inclined to the horizon at an angle of 
some 70°, the water having followed, as is its wont, the 
direction of least resistance, viz., one of the sets of joint 
planes. The gorges of the Pantenbriicke, the Aar above 
Im- Hof, with many others, might be quoted as instances 
of the same. We think, indeed, that in arguing against 
those who ascribe alpine sculpture mainly to fracture, 
the professor does not quite do justice to the influence which 
fissures, faults, and joints (which last may, in many cases, 
be connected with the others) exercise in directing the 
meteoric agents. These have not, indeed, fashioned the 
mountains, but they have obliged the sculpturing forces 
to work in certain directions, have been like the rails or 
the points which cause a locomotive to follow a particular 
course instead of wasting its power in wandering over the 
fields. 
Further on in the chapter, Prof. Tyndall refers to his 
own favourite theory of glacier sculpture, with regard to 
which he expresses himself more guardedly than in the 
paper originally published in the Phzlosophical Maga- 
zine (vol. xxiv. p. 169). Still we cannot say that we are 
convinced by his arguments even in their modified form, 
No one, of course, would deny that a glacier can deepen 
its bed ; the question is simply one of degree. With re- 
gard to this our space will allow us to do little more than 
express dissent, and indicate one or two points where, 
while not disputing Prof. Tyndall’s facts, we cannot ac- 
cept his inferences. 
The silt which is brought down by a glacier stream 
cannot, we think, be taken as a measure of the abrasion 
exercised by the glacier; surely the greater part is de- 
rived from the stones crushed between the ice and rock ; 
it is the grist from the glacier mill, rather than the detritus 
of the nether stone. We fail also to see how, unless 
under exceptional circumstances, a glacier can “ do more 
than abrade.” Granted that “rocks are not homo- 
geneous, they are intersected by joints and places of 
weakness which divide them into virtually detached 
masses,” we doubt if it follows that “a glacier is un- 
doubtedly competent to root such masses bodily away.” 
A heavy body sliding over such masses and in close con- 
tact with them, would, we think, be more likely to keep 
them in their place, and certainly rocks from which 
glaciers have retreated do not exhibit evidence of this 
kind of erosive action. We confess, therefore, to still 
regarding the effects of glaciers as comparatively super- 
ficial, and classing the ice ploughs of past ages as among 
the efforts of scientific imagination. 
A considerable portion of the latter part of the volume 

is devoted to a véswmé of the “ viscous” and “ regelation ” 
theories of glacier motion ; a controversy which can hardly 
yet be regarded as concluded, seeing that the experiments 
of Mr. Mathews and Mr. Froude, to which Prof. Tyndall 
briefly alludes, appear likely to have a very important 
bearing upon the question of whether or not ice under 
any circumstances is a flexible or plastic substance to an 
appreciable extent. 
Among the very miscellaneous scraps with which 
the volume terminates, is an account of the voyage to 
Algeria to observe the Eclipse. This, so far as its 
main purpose went, was a dismal failure, but remarks 
are introduced on the colour of the sea and sky, a subject 
already treated by the author in his “Glaciers of the 
Alps.” During the voyage home a number of bottles of 
sea-water were secured from various stations, which were 
afterwards examined in London by passing through them 
a beam of electric light—the purity or impurity of the 
water is then shown by the less or greater amount of light 
which it scatters. Briefly, the result was that the dark 
blue water was very pure, the cobalt-blue rather less so, 
while the green tints denoted the presence of much sus- 
pended matter, and the yellowish green was very thick. 
A remarkable instance of this variety of colour which, if 
our memory serve us, he has not quoted, isin the Lakes 
of Thun and Brienz ; the waters of the latter, which re- 
ceives the silty streams of the Aar and the Lutschine, are 
distinctly green, while those of the former, into which no 
important glacier torrent directly enters, are of a beautiful 
blue. 
In fine, though there is little new about the book, 
many of Prof. Tyndall’s admirers will be glad to possess 
in a convenient form so many thoroughly characteristic 
papers, displaying at once his thoughtful mind and 
intense love of nature, as well as his great command over 
nervous and picturesque English. 
T. G. BONNEY 


OUR BOOK SHELF 
Tir ™” ‘ural History of Plants. By H. Baillon. Trans- 
} “ sy Marcus M. Hartog. Vol. I. (London: L, 
Rewarais Co. 187t.) 
HAVING noticed, on its publication, the first volume of 
Prof. Baillon’s “Histoire des Plantes” (see NATURE, 
vol. i, p. 52) we need scarcely do more than call atten- 
tion to the English edition which now lies beforeus. The 
translation, we may say at the outset, appears to us to be 
well done ; the meaning of the original is, as far as we 
have observed, carefully preserved ; and a better know- 
ledge of his subject is shown by the translator than is 
always the case in English renderings of foreign scientific 
works. The co-ordination of the natural orders followed 
in the work is, as was mentioned in our notice of the 
original, novel ; whether it will stand is a question on 
which we ought not, perhaps, to express an opinion until 
the plan is more fully developed. We could have wished 
that the author had given in this first volume some general 
sketch of his new system, with a defence of its peculiari- 
ties. So competent an authority as Prof. Baillon cannot 
have departed from the ordinary arrangement without 
cogent reasons, which we should have liked to have known. 
It is always a great advantage to English systematists to 
know the views of their fellow-workers on the Continent. 
We miss also the great assistance that is afforded to the 
systematist by a tabulated clavis of the genera belonging 
to each natural order. The amount of information con- 
