534 
NATO TLE 
[March 24, 1870 
become incorporated with the post-cretaceous continent,* it is 
with much satisfaction that I find views for the most part so 
similar developed by Professor Huxley with the ability which 
marks all his work. Nevertheless, I venture to submit that the 
view I then advanced as to the period of the origin of the 
Eocene types is more in accordance with the /acts, as far as we 
know them, than the hypothesis of their origin in a detached 
province during the Mesozoic period. 
The view I advanced was that great changes in the distribution 
of the continents and seas took place at the close of the Palazo- 
zoic, and again at the close of the Mesozoic epoch ; and so far I 
am at one with Professor Huxley : but I inferred that the geo- 
graphical changes taking place at the close of the Mesozoic epoch 
were accompanied by the formation of a continent extending 
over all the geologically known parts of the globe, whose endur- 
ance was so prolonged as to have afforded the necessary time for 
the evolution upon it of the Eocene types. 
In support of this inference I dwelt upon the entire disappear- 
ance of the orders Pterosauria, Enaliosauria, and Dinosauria 
among vertebrates, and of the Ammonitide among invertebrates; 
as well as upon the great extinction that took place in various 
other forms of life. Such a process as the one suggested by Mr. 
Huxley would lead us to look in Eocene strata for an interming- 
ling of these distantly evolved types with forms belonging to the 
several orders just named ; however much these forms might in 
their specific, or even in their generic characters, have been 
changed during the interval in which these distantly evolved 
types were introduced. But instead of this we find an absolute 
disappearance of several important orders of life, of which, from 
their aditat, some—especially the Pterosauria—would seem to 
have been independent of geographical changes simply. 
Mr. Huxley intimates that he is led to his view by arguments 
which he had previously used to demonstrate the necessity of the 
existence of all the Eocene types in some period antecedent to 
the Eocene; but may we not suppose that the interval thus 
marked by the disappearance of so many great orders was vast 
enough even for this evolution? Indeed so much did this great 
extinction weigh upon me that even the intervention of a vast 
lapse of time seemed scarcely sufficient ; and I felt driven to sup- 
pose that these geographical changes in some degree altered the 
general conditions under which life had previously existed ; and 
that this alteration, while stimulating evolution on the newly- 
formed continent, contributed to the great extinction which 
marks the intra-cretaceous and Tertiary epoch. 
Subtle as are the causes which have brought into existence the 
various types of being, those which have produced their extinc- 
tion are not less so; though they have not yet received that 
attention which has been directed to the origin of species. I 
feel how crude were the suggestions I offered in 1860 to explain 
this great extinction, and how wide a field of conjecture upon the 
subject is left open ; for these orders of life were not only various 
in their /aéditat, but equally various in their food. We may 
imagine the extinction of a species to take place from failure of 
its food, from destruction by enemies, or—and I think this may 
be a cause more potent than any other, especially with forms 
possessing great fecundity—by a failure of the reproductive func- 
tion ; just as among men families diminish and eventually leave 
no descendants. Be the causes, however, what they may, this 
great extinction requires us, I submit, to suppose the occurrence 
of an interval of time as great, and accompanied by changes of 
conditions as complete, as any that we can urge as necessary for 
the evolution of the Eocene types. Moreover, the cretaceous 
period itself, whose terrestrial fauna is as yet unknown, may, so 
far as we yet know to the contrary, have witnessed in the Euro- 
pean area the commencement of, or even some progress in, the 
evolution of the Eocene types. 
Brentwood, March 10 SEARLES V. Woop, Jun. 
Transactions of the Royal Society of Edinburgh 
WITH reference to G.’s letter in the last number of NATURE, 
I have merely to observe that (as you will see by the accom- 
panying list) the Transactions of the Royal Society of Edinburgh 
are regularly sent to no less than twenty-three different societies, 
institutions, or museums in London alone—besides being sent 
* “On the probable events which succeeded the close of the Cretaceous 
period ;” read before the Geological Society on February rst, 1860. The 
publication of the paper, beyond a brief abstract, having been denied by the 
Council, the desideratum was kindly supplied by Dr. Francis ; and the paper 
in extenso is given in the Philosophical Magazine of March, April, and May, 
1862; the title having been changed to ‘“‘ The form and distribution of the 
Land Tracts during the Secondary and Tertiary periods, &c.” 
to many Honorary and Ordinary Fellows residing there. As 
regards the special case of the British Museum, I have in my 
possession at this moment their acknowledgments of receipt 
of the successive parts of our Transactions up to March 1869, 
and expect immediately to hear that they have received our last 
published Part. J. H. Batrour, Sec. R. S. Edin. 
Euclid as a Text-Book 
“THE first four books of Euclid : or the principal properties 
of triangles, and of squares and other parallelograms treated 
geometrically : the principal properties of the circle and its in- 
scribed and circumscribed figures treated geometrically.” Such 
is the wording of the programme put forth by the University of 
London, of the Mathematical portion of the examination for 
matriculation candidates, Whether the papers have ever been 
drawn up in accordance with it I cannot say, but certainly my 
experience for the last four or five years has led me to believe 
that the alternative side has, of late, at least, been altogether 
ignored. 
The slightest inspection of recent papers will show that they 
are constructed on the Euclidean type, and so long as Euclid 
was generally taught in schools, I think rightly so. But that 
such a course should now be persisted in (with such latitude as 
the pragramme provides) is hard upon those establishments 
which have taken up the modern views of the subject, such as 
those so ably advocated by Professor Hirst,* and Mr. J. M. 
Wilson of Rugby.t+ It can hardly be thought that so advanced 
an examining body as the London University will continue to 
act as an obstructive—for non-encouragement is almost tanta- 
mount to tabooing the subject; and the practical result of per- 
sistence, I fear, will be this, that the course pursued will press 
unfairly upon those schools in which (as in University College 
School, where Wright’s Geometry is now the text-book) Euclid 
has been almost ¢ discarded. Boys are required to study 
in their school work this modern geometry, founded on French 
mathematical works; and yet, seeing what value is set upon the 
same in the examination papers I am discussing, feel themselves 
constrained to read Euclid that their prospects of good places 
may be enhanced. 
I am disposed to believe that ‘‘something will shortly be 
done,” but the reform, though it ought rightly to commence 
here, ought not to stop here. Every examining body, if a fair 
field is to be given to the students of modern geometry, should 
put forth a scheme similar to that which heads my letter, and 
not merely put it forth ‘fas a sop to Cerberus,” but act upon it 
and let it be a reality. 
University College School R. TucKER 
MECHANICAL PROPERTIES OF ICE, AND 
THEIR RELATION TO GLACIER MOTION 
aX FEW weeks ago I prepared for the February num- 
ber of the Alpine Fournal a review of the contribu- 
tions made by the Rev. Canon Moseley to the theory of 
glacier motion, which have appeared at various times 
during the last fifteen years in the Proceedings of the 
Royal Society and the Philosophical Magazine. Some 
new facts having come to my knowledge since the publi- 
cation of my paper, I venture to recur to the subject, and 
to invite discussion upon those memoirs of Canon Moseley 
in which he endeavours to prove that the descent of 
glaciers by their weight alone is a mechanical impossi- 
bility.§ The arguments he advances in support of this 
conclusion may be epitomised as follows :— 
If a transverse section of a glacier were to be made, the 
ice would be found to be moving differently at every point 
of it. The velocity is greater at the surface than deeper 
down, at the centre of the surface than the edges. There 
is a constant displacement of the particles of ice over one 
another, and alongside one another, to which is opposed 
the resistance known as shearing force. By the property 
of ice called regelation, where a surface so sheared is 
* In his college lectures, and lectures to ladies at St. George’s Hall, &c. 
+ ‘Euclid as a text-book of Elementury Geometry” (read before the 
London Mathematical Society, and printed in the Lducational Times, Sept. 
1868), and in his ‘‘ Elementary Geometry.” 
t Almost. In consequence of pressure from without, arising from the cir- 
cumstances with which my letter deals, Euclid is again read in one class. 
§ Proceedings of the Royal Society, Jan, 7, 1869. Philos, Mag., May 
1869. Philos. Mag., Jan. 1870. 
