114 
The May number of the Yournal of the Chemical Sociely opens 
with an important paper by Mr. W. H. Perkin on “ Artificial 
Alizarin.” He first gives a sketch of the notions entertained by 
chemists as to the composition and relations of this important 
colouring matter prior to the investigations of Messrs. Graebe 
and Liebermann. These chemists showed that by treating 
alizarin cbtained from madder with powdered zinc, a hydrocarbon 
was produced of the composition C,, Hy) and possessing all the 
properties of the anthracene of coal tar. By oxidising anthracene 
it is converted into anthraquinone C,, H, O, ; by the action of 
bromine dibromanthraquinone C,, Hg, Br, O, is produced, and 
by subsequent treatment with potassic hydrate at a high tempe- 
rature, an alkaline solution of alizarin C,, Hg Oy is obtained— 
being the first instance of the artificial formation of a natural 
colouring matter. Mr. 'Perkin, in England, and Messrs. Caro, 
Graebe, and Liebermann, in Germany, have succeeded in 
obtaining the alizarin without the use of bromine. This may be 
effected by treating the anthraquinone with strong sulphuric acid, 
when disulphanthraquinonic acid C,, Hg O, (HSOs), is formed, 
and this, when digested with potassic hydrate at 180°, gives rise 
to potassic sulphate and the potash compound of alizarin. The 
alizarin prepared from anthracene is identical with that extracted 
from madder. It has the same appearance, behaves in the same 
manner with reagents, produces the same effects in the dye bath, 
and exhibits the same absorption bands when examined spectro- 
scopically. ‘Two patterns dyed with artificial alizarin accompany 
the paper.—-The second;paper is by Mr. John Hunter, and con- 
tains some ‘‘ Analyses of Deep Sea Water, and of some Ooze 
from the bottom of the Atlantic,” collected during the expedition 
of H.M.S. Porcupine.—We then have a paper by Dr. Gladstone, 
on the “ Refraction Equivalents of Aromatic Hydrocarbons and 
their Derivatives,” being a continuation of the subject of the lec- 
ture reported in the previous number. Messrs. T. Bolas and C. 
E. Groves have experimented on the preparation of bromopicrin, 
They give exact directions for the preparation of this substance 
by acting on picric acid with bromide of lime, a compound analo- 
gous to bleaching powder. Bromopicrin has a very high specific 
gravity, 2°811 at 12°5°C. The authors announce that they 
have obtained the carbonic bromide CBr, by acting on bromo- 
picrin with powerful brominating agents.—The concluding paper 
is by Prof. How, enan ‘‘ Acidified Water from the Coal-field of 
Stellarton, Nova Scotia.” This water was found to be distinctly 
acid, in consequence of its containing a considerable quantity of 
free sulphuric acid, probably produced from the iron pyrites 
present in the coal strata. 
SOCIETIES AND ACADEMIES 
LONDON 
Royal Society, May 19.--‘‘On the Cause and _ Theoretic 
Value of the Resistance of Flexure in Beams.” By W. H. 
Barlow, F.R.S. 
The author refrs to his previous papers, read in 1855 and 1857, 
wherein he described experiments showing the existence of an 
element of strength in beams, which varied with the degree of 
flexure, and acts, in addition to the resistance of tension and 
compression of the longitudinal fibres. It was pointed out that 
the ratio of the actual strength of solid rectangular beams to the 
strength, as computed by the theory of Leibnitz is, in cast iron, 
as about 2} to 1; in wrought iron as 1 and 1} to I ; and in 
steel, as 12 and 1}to 1. The theory of Leibnitz assumes a beam 
to be composed of longitudinal fibres only, contiguous, but un- 
connected, and exercising no mutual lateral action. But it is 
remarked that a beam so constituted would possess no power to 
resist transverse stress, and would only have the properties of a 
rope. Cast iron and steel contain no actual fibre, and wrought 
iron (although some qualities are fibrous) is able to resist strain 
nearly equally in any direction. The idea of fibre is convenient 
as facilitating investigation ; but the word fibre, as applied to a 
homogeneo. elastic solid, must not be understood as meaning 
filaments of the material. In effect it represents lines of direc- 
tion, in which the action of forces can be ascertained and measured, 
for in torsion-shearing and ‘‘ angular deformation” the fibres are 
treated by former writers as being at the angle of 45°, because it 
has been shown that the diagonal resistances have their greatest 
manifestation at that angle. Elastic solids being admitted to 
possess powers of resistance in the direction of the diagonals, 
attention is called to omission of the effect of resistance in the 
theory of beams, The author then states, as the result of his in- 
NATURE 
[Fune 9, 1870 
vestigation, that compression and extension of the diagonal fibres 
constitute an element of strength equal to that of the longitudinal 
fibres, and that flexure is the consequence of the relative exten- 
sions and compressions in the direct and diagonal fibres, arising 
out of the amount, position, and direction o; applied forces. 
Pursuing the subject, it is shown that certain normal relations 
subsist between the strains of direct fibres and their relative dia- 
gonals, evenly distributed strain being that in which the strain{in 
the direct fibres is accompanied by half the amount of strain in 
the relative diagonal fibres. Any disturbance of this relation in- 
dicates the presence of another force. Thus tensile forces applied 
at right angles to compressive forces of equal amount, produce 
no strain in the diagonals. But if forces applied at right angles 
to each otherare both tensile, or both compressive, the strain in 
the diagonal is as great as that in the direct fibres. It is also 
pointed out that in a given fibre a, 4, c, the point may be moved 
with regard to a and c, thus producing plus and minus strains in 
the same fibre. Treating a solid as being made up of aseries of 
laminz, and showing that every change of figure can be repre- 
sented by the variation in length of the diagonals, taken in con- 
nection with those of the direct fibres, the author proceeds to 
trace the effects of the application of tensile and compressive 
forces acting longitudinally on either side of the neutral plane, 
and shows that curvature is the result of the relation between the 
strains in direct fibres and those in the diagonals. The opera- 
tion of a single tensile force applied along one side of the plate 
and a transverse stress are likewise traced out, and the conditions 
of ‘elastic equilibrium” referred to. The amount of resistance 
offered by the diagonal fibres is shown as follows :— 
é 
a 
Fb 
a, b, c, d represents a portion of a beam strained by transyerse 
forces into the circular curve a, e. Two resistances arise. 1. 
That due to the extension and compression of the longitudinal 
fibres produced by the rotation of 4, @ about the neutral axis, 
which is the resistance considered in the theory of Leibnitz. 2. 
That due to the extension and compression of the diagonal fibres, 
caused by the deformation of the square a, 4, c, d into the figure 
a, h, 0, c, which is the resistance of flexure. It is then shown 
that in a solid rectangular beam, the second resistance is equal to 
the first, and that both resistances act independently, and conse- 
quently that the true theoretic resistance of a solid rectangular 
beam is exactly twice that arrived at by the theory of Leibnitz. 
The strength so computed is in general accordance with the 
results of experiments in cast iron, wrought iron, steel, and other 
materials, the maximum strength being tound in cast iron, which 
is one-eighth above, and the minimum in glass, which is one- 
fourth below the calculated strength. The author considers this 
treatment of the subject as arising necessarily out of Dr. Hook’s 
law “‘ut tensio sic vis,” and that it is in effect completing the 
application of those principles which are only partially applied 
by Leibnitz. The paper concludes with some practical illustra- 
tions (accompanied by photographs) of the effect of diagonal 
action. The appendix contains the results of experiments on the 
tensile, compressive, and transverse resistances of steel. 
“©On some Elementary Principles in Animal Mechanics. — 
No. tv. On the difference between a Hand and a Foot, as 
shown. by their Flexor Tendons.” By the Rev. Samuel 
Haughton, M.D. Dubl., D.C.L. Oxon, Fellow of Trinity 
College, Dublin. 
The fore feet of vertebrate animals are often used merely as 
organs of locomotion, like the hind feet; and in the higher 
mammals they are more or less ‘‘ cephalised,”’ or appropriated as 
hands to the use of the brain. The proper use of a hand when 
thus specialised in its action, is to grasp objects; while the 
proper use of a foot is to propel the animal forward by the inter- 
vention of the ground, In the case of the hand, the flexor 
