140 
NATURE 
He then proceeds to compare the calculated resistance 
of certain simple beams with the observed resistance as 
ascertained by experiment, and he finds that there is a 
large discrepancy between the calculated and the experi- 
mental ultimate resistances. Adopting Mr. Barlow’s | 
notation, hecalls / the ultimate resistance to direct tension, 
F the “apparent” resistance to the same force excited by 
transverse strain, and ¢@ the “resistance due to flexure,” 
then # = f+. This will be better understood by re- 
ference to figures. Mr. Hodgkinson found in the experi- 
ment under consideration, that a square inch of cast iron 
was ruptured under direct tension by 18,750lb., which in 
the above equation would be the value of f/ When, how- 
ever, a rectangular bar of the sae material, one inch 
square, was tested, a weight of 527lb. applied at the centre 
of a span of sixty inches, just broke the bar. Applying 
now the formulz for rectangular beams to this result, the 
author finds that the ultimate tensile strength of the 
sample under consideration must be assumed at 45,630lb. 
in order that the bar may be able to offer the resis- 
tance shown in the experiment ; the figure 45,630 he calls 
the “apparent” tensile strength, and would be the value 
of / in the above equation ; accordingly, 45,630 = 18,750 
+ ¢, or @ = 26,880lb., this value of @ being termed 
“resistance due to flexure,” a term, we are informed, in- 
vented by Mr. W. H. Barlow; * and this new resistance 
being described as “lateral adhesion of the fibres ;” and 
the author informs us, that the neglect of it may result in 
an error up to 190 per cent. 
We have here a fine confusion of everything referring 
to the subject. An error is made, which to explain away, 
anew one must be committed; forces hitherto not sus- 
pected by mathematicians are discovered by those whose 
sound judgment was not checked in its growth by the 
infinitesimal calculus. 
Does the author not know the condition which deter- 
mines the position of the neutral axis of a beam? The 
neutral axis passes through the centre of gravity of the 
sectional area of a beam, provided ¢he resistance of the 
material to tension and to compression be alike, In almost 
every material these resistances differ from one another, 
but when only a small fraction of the ultimate resistance 
of the material need be taken into account—say one fourth 
—then for practical purposes they may be assumed to be 
alike. 
The author proceeds, however, to breaking strain, using 
cast iron ; its ultimate resistance to tension is about eight 
.tons per square inch, to compression about forty tons. 
Under these circumstances his original formula no longer 
holds good; the neutral axis no longer passes through the 
centre of gravity of the section of the beam, it approaches 
more and more the side where the greater resistance is 
offered ; and were the resistance to compression infinitely 
great, the neutral axis would coincide with the position of 
the extreme fibre of the beam on the compression side, 
and the whole sectional area would be resisting tension 
only, and the extreme fibre balanced by compression. 
The beam would then have just double the resistance 
without assuming the least increase of tensional resistance 
of the material. The authoz’s ¢ expresses, therefore, the» 
amount of error into which he and others have fallen, and 
in case it should be zero, they will find F = fas it should 
be, and the elaborate fabric of confusion disappears. 
In other respects, the work contains much valuable in- 
formation, and if the unfortunate mistake above referred 
to, did not crop up throughout the 300 pages, and a 
natural flow of clear language were substituted for a rather 
dogmatic and vague style, we should be glad to recom- 
mend it to the profession, which ought to have all the aid 
that modern science can afford. ue Sy 
* Mr. Barlow, F.R.S., recently read a paper before the Royal Society on 
this subject, reviving his theory on the resistance of beams to transverse 
strain. 
| 
[ Fune 23, 1870 
Meteorology. By Sir John F. W. Herschel, Bart. From 
the Encyclopzedia Britannica. Second Edition, (Edin- 
burgh ; A. & C. Black.) 
Introductory Text-book of Physical Geography. By D.Page. 
Fourth Edition, (Edinburgh : W. Blackwood & Sons.) 
WE class these two books together as new editions of 
standard treatises in their respective departments of 
science that are among the best that can be used by stu- 
dents or teachers. The term “ Meteorology,” which has 
entirely lost its etymological meaning, is defined by Sir 
John Herschel as “the description and explanation of 
those phenomena which group themselves under the head 
of the weather, of the seasons, and of the climate,” a 
branch of natural science of the laws regulating which 
we are at present almost entirely ignorant, as Dr. Balfour 
Stewart has shown in these pages. Writers on physical 
geography content themselves at present with a descrip- 
tion of the physical contour of the globe, with some slight 
reference to its climatology, and the distribution of its 
animal and vegetable life, Mrs. Somerville’s handbook 
being, as far as we know, the most complete in this re- 
spect. The better and more logical mode would seem 
to us to be, first of all to treat of the earth as a mem- 
ber of the solar system, and thence to deduce the laws 
which govern its natural phenomena ; we believe that in 
this way such phenomena as those of ocean currents and 
trade winds, and the variations of climate, would be ren- 
dered far more quickly intelligible to the learner than is 
now the case. From his stand-point, Dr. Page’s “ Intro- 
ductory Text-book” discusses the subject in his usual 
clear, concise, and systematic manner. 
Rustic Adornments for Homes of Taste. By Shirley Hib- 
berd. New Edition. (London : Groombridge & Sons.) 
THAT two editions of this book have been disposed 
of in a short time is ample justification for the publication 
of a third, especially when got up in so handsome a style 
as the one before us. Works of this kind appeal toa large 
public, not over-critical as to scientific accuracy, but glad 
to possess that amount of knowledge which enables them 
to talk about ferneries and aquaria without committing 
any egregious blunder. We are far from depreciating the 
value of this smattering of science where it is all that 
opportunity permits to be attained. Those who like their 
homes to be surrounded by beautiful natural objects will 
here find a large fund of information respecting the aqua- 
rium, the fernery, the aviary, the apiary, the conservatory, 
&c., given in a pleasant style, illustrated with wood- 
cuts and coloured plates. The volume makes altogether 
a very pretty gift-book, especially for a young lady. 
E. Millon, sa Vie, ses Travaux de Chimie, et ses Etudes 
économiques et agricoles sur l Algérie, Pp. 327. (London: 
Williams and Norgate, 1870.) 
M. REISET, in the preface, tells us that after the death 
of Millon, his friends and pupils undertook the publi- 
cation of a collection of abstracts of the numerous works 
of this illustrious chemist. The book commences with an 
interesting biographical notice of Millon, by Dr. Heefer, 
in which the political questions which led to his long resi- 
dence in Algeria are as slightly noticed as possible. The 
principal portion of the volume was arranged by M. 
Jules Lefort, with the assistance of MM. Coulier, Com- 
maille, and the late Professor Nicklés. The book contains 
two hitherto unpublished papers, each extending over 
forty-three pages, one “on Fermentation” and the other 
“on the Economic and Agricultural problem of Algeria.” 
The researches on corn also occupy considerable space. 
The other investigations of Millon are arranged in a very 
interesting manner, frequently in connected treatises. 
Opposite the title-page is a good photograph of a bust by 
M. Clément, and at the end of the book is a chronological 
list of the scientific works of the author, amounting in 
number to no less than seventy-nine, 
