484 
NATURE 
[ MarcH 21, 1907 
dissected Flysch-zone, and that the contrast between 
the surface of the young folded chain and that of 
the old ‘‘ Rumpf ’’ of Bohemia is in reality a develop- 
ment of fairly recent The Alps, moreover 
(p. 18), appear to have gained in height, by a vertical 
movement, 
lakes, and thus their present preeminence is not to 
be ascribed to lateral thrust alone. 
The uniformity of level of peaks in the same dis- 
trict is then discussed, and it is argued that the 
cutting of valleys in a mass undergoing denudation 
influences the heights of the peaks along the valley- 
walls. After a long time, where the hardnesses of 
the rocks concerned do not greatly vary, the up- 
standing points at any given distance from the centre 
of the chain will tend to be reduced to much the same 
level above the sea, and the impression given will 
be that they were originally points on a _contin- 
uous dome. It is clear that the author here asks us 
to be cautious in applying the fascinating doctrine 
of the ‘*‘ peneplain’’ and of subsequent elevation to 
every dissected highland. 
The consideration of the post-Pliocene uplift leads 
us on to the vigorous and partly post-Roman de- 
pression of the Adriatic region, with the compensating 
elevation of the Apennines; then follows a survey of 
river-courses in central Europe. The movement of 
masses of land in vertical blocks, to which geomorpho- 
logical studies in the Alps have directed attention (p. 
36), is shown not to be inconsistent with horizontal 
movements, and with folding, where one block rides 
over another (p. 34). The relative importance of 
vertical movement and horizontal thrusting, and how 
far the one may be a manifestation of the other, are 
left as problems for the future. 
So far, the results of recent observation, geo- 
graphical it may be, but with a remarkably geo- 
logical trend, have been summarised for the region 
of which Vienna is the natural centre. 
in praise of observational research conclude this 
section. The title of the pamphlet is, however, really 
justified in the discourse to the students of Berlin, 
which opens with a somewhat depressing picture of 
their natural environment. Men, not mountains, 
have made the greatness of the geographical school 
of northern Germany. Prof. Penck contrasts the in- 
fluence of Karl Ritter, who regarded the earth from 
the point of view of its suitability for man, with the 
later and more scientific attitude of von Richthofen. 
In each case the geographical outlook depended on the 
stage reached contemporaneously in the development 
of scientific thought. Ritter expressed (p. 47) the teleo- 
logical views of his time; Richthofen ‘‘nimmt die 
Erdoberflache nicht als gegeben, sondern als geworden, 
naturgemass daher bei ihm die enge Fiihlung 
zwischen Geographie und Geologie.’ Followers of 
Richthofen should insist on being observers, not mere 
critics and coordinators. Modern means of com- 
munication have made travel a matter of money only, 
instead of both time and money, as in bygone years. 
The small scale of the maps of the more recently 
explored countries masks the immense amount. of 
NO. 1951, VOL 75] 
times. 
since the formation of the interglacial 
A few words 
work that is waiting to be done, and the district 
adjacent to a colonial railway station may well 
reward the student who goes out skilled in observ- 
ation. With such stimulating words Prof. Penck 
enters on his new province in Berlin, and he may be 
sure that his friends in the four corners of the world 
will welcome those whom he has trained. 
GRENVILLE A. J. COLE. 
THE STRENGTH OF MATERIALS. 
Text-book on the Strength of Materials. By S. E. 
Slocum and E. L. Hancock. Pp. xii+314. 
(Boston and London: Ginn and Co., n.d.) Price 
12s. 6d. 
HIS book is intended to provide for the needs 
of engineering students both in the class-room 
and in the laboratory; hence it is divided into two 
parts, the first part treating of the theoretical side 
of the subject and the second dealing with the ex- 
perimental side. The first two chapters are devoted 
to a general discussion of the relations between stress 
and strain as an introduction to the development of 
the more special rules applicable to the structural 
forms in common use by engineers and architects. 
There is an unfortunate slip on p. to in the para- 
graph dealing with the fatigue of metals; in quoting 
some of the results obtained by Bauschinger in his 
experiments, the material is stated to have been 
“cast iron’’—it was, of course, ‘*‘ wrought iron.” 
Chapters iii. and iv. deal with stresses and strains 
in beams, and there are two useful constructions not 
usually found in text-books on this subject, namely, 
a graphical method of finding the centre of gravity 
and the moment of inertia for a rail, or other similar 
section, and a graphical solution of the problem of 
finding the moment of inertia of a reinforced con- 
crete beam of rectangular cross-section. 
In dealing with the flexure of beams in chapter iv., 
the problem of continuous beams is fully discussed, 
and, in addition to the method of three moments, 
other methods of solution of the problem, based on 
Maxwell’s theorem and on Castigliano’s theorem, are 
explained. 
In the next two chapters the design of struts and 
shafts is dealt with, also the theorem of helical 
springs, but there is nothing novel in the treatment 
of any of the problems which have to be solved. 
In the chapter which treats of the strength of 
spheres and cylinders under uniform pressure, a neat 
formula is obtained for the critical pressure just pre- 
ceding collapse in the case of a hollow circular 
cylinder subjected to external pressure, and Lamé’s 
formula for thick cylinders is deduced. 
Two subjects—flat plates and hooks—which in 
most of the text-books are usually treated in a some- 
what unsatisfactory fashion are thoroughly investi- 
gated in chapters viii. and ix.; in the case of crane 
hooks it is pointed out that the ordinary assumption 
that the distribution of stress is the same as in a 
straight beam subjected to an equal bending moment 
and axial‘load is not even approximately correct. 
From an analysis of the stresses in a curved piece 
subject to pure bending strain, a general formula for 
