Fune 17, 1886] 
NATURE 
159 
enjoy a property capable of being stated in advance, it consti- 
tutes for him an event (wz événement). By means of some 
extremely difficult and subtle analytical transformations he 
arrives at a very general and remarkable formula, by means of 
which he solves with the greatest ease a number of curious arith- 
metical problems, such as: ‘‘ What probability is there that in 
any given division the most approximate quotient will be the 
quotient by default (far #éfau/)? What probability is there 
that, if an integer taken at hazard be divided by the sum of two 
other integers taken at hazard, the quotient by default will be an 
odd number ?”—On the oxidation of hydrochloric acid under the 
influence of light, by M. Leo Backelandt. This paper deals with 
the phenomenon observed by the author, that concentrated pure | v : 
| turns of insulated wire. 
hydrochloric acid exposed to the action of sunlight in a badly- 
stopped flask after some time turns yellow, and emits an odour of 
chlorine. The change is shown to be due to a process of oxida- 
tion, the atmospheric oxygen consuming the hydrogen of the 
hydrochloric acid and liberating the chlorine. Under analogous 
circum-tances hydriodic acid acts in the same way, liberating 
its iodine.—Notes on the rocks of Kantavu Island, Fiji Archi- 
pelago, by M. A. Renard. The author deals mainly with the 
andesites of the port of Kantayu, where they assume a columnar 
disposition. —Examination of the objections made by M. Hirn 
against the kinetic theory of the gases, by M. R. Clausius. 
While admitting the general care and accuracy with which 
M. Hirn has conducted his extensive experiments, the 
author argues on theoretical grounds that they are in no 
way opposed to the now generally accepted kinetic theory. 
Rendiconti del Reale Tstituto Lombardo, April 15.—On the 
permanent magnetism of steel at various temperatures, by Dr. 
G. Poloni. In this paper, which is supplementary to the two 
memoirs published by the author in 1878 and 1882, several in- 
teresting experiments are described with a series of magnets 
subjected to the action of heat within the limits of 15° and 300° 
C.—Note on a new acid isomerous with aspartic acid, by Prof. 
G. Korner. The formula of this acid, which the author pro- 
poses to name a-iso-asparlic or a-amido-isosuccinic acid, is— 
CHy 
| —co,4 
—NH, 
CO,H. 
Rivista Sctentifico-Industrial’, April 15.—A new method of 
measuring the thermic expansion of solid bodies, by Prof. Filippo 
Artimini. The author describes an ingenious apparatus which 
he has constructed for the purpose of determining with sufficient 
accuracy the increase in the linear dimensions of solids, derived 
from the internal motion communicated to matter by thermic 
energy. 
April 30-May 15.—On the real atomic heat of simple bodies 
in the mechanical theory of heat and the formulas relating to it, 
by Prof. Alessandro Sandrucci, In Hirn’s ‘‘ Mechanical Theory 
of Heat” the expression veal atomic heat is applied to the pro- 
duct of the atomic weight @ of a simple body by its absolute 
calorific capacicy A and it is shown that this quantity should be 
independent of temperature, and equal and constant for all 
existing simple bodies ; but the deductions are established inde- 
pendently of any hypothesis on the nature of heat. Prof. San- 
drucci now inquires whether, given a certain hypothesis on the 
nature of heat, and determining the physical concept of veal 
atomic heat in said hypothesis, it might be possible to obtain 
general and numerical results equal, or very nearly equal, to 
those already found by Hirn.—On a new saponiferous plant, by 
Prof. G. Licopoli. To the Sufonaria officinalis, the Quillaja 
Safonaria, and a few other plants of this class Prof. Licopoli 
now adds the Znerolobium Timbouva, Martius, which is widely 
diffused throughout South Brazil and Uruguay. 
SOCIETIES AND ACADEMIES 
LONDON 
Royal Society, May 20.—‘‘On the Lifting Power of Elec- 
tro-Magnets and the Magnetisation of Iron.” By Shelford 
Bidwell, M.A. 
If an electro-magnet be excited by a gradually increasing 
increase of sustaining power to increase of current becomes 
rapidly smaller ; and it has generally been assumed that this 
ratio continues to diminish indefinitely, so that an infinite current 
would not impart toa magnet much greater lifting power than 
that which it possesses when an approach to ‘‘saturation” is 
first indicated. Joule estimated that the attraction would never 
be as much as 200 Ibs. per square inch of sectional area; and, 
much Jater, Rowland assigned 177 lbs. per square inch, or 
12,420 grms. per square centimetre as the limit for iron of good 
quality. 
Having reason to doubt these conclusions, the author made 
some experiments with an iron ring cut into two equal parts, 
each of which was surrounded by a coil containing nearly 1000 
When one-half of the ring was used 
as an electro-magnet, and the other half as an armature (no 
current being passed through its coil), the weight supported was 
with a current of 4°3 amperes 13,100 grms., and with 6°2 
amperes 14,200 grms., per square centimetre of surface. The 
lifting power therefore exceeded that which had been previously 
considered the greatest possible ; nor was there any indication 
that a limit was being approached. But it was of greater in- 
terest to observe the effects produced when éo¢4 portions of the 
ring were brought under the influence of gradually increasing 
currents, the conditions then being nearly the same as in Row- 
lind’s experiments. It was found that when the magnetic force 
had reached 50 C.G.S. units, at which point the weight sus- 
tained was about 10,000 grms. per square centimetre, the falling 
off in the rate of increase of the lifting power was well marked. 
And it continued to diminish until the magnetic force was 250 
units and the weight supported 14,000 grms. But from this 
point che magnetising current and the weight that could be carried 
increased in exactly the samz proportion, and continued to do 
so until the magnetic force had been carried up to 585 units, 
when the experiment was stopped, the maximum weight sup- 
ported having been 15,905 grms. per square centimetre, or 
229°3 lbs. per square inch. Detailed results are given in the 
first and second columns of the table. A curve plotted with 
the magnetic forces as abscissee, and the weights lifted as ordi- 
nates, becomes, when the magnetic force is greater than 240: 
units, a sensibly straight line inclined to the horizontal axis. 
It occurred to the author that these results might be applied 
to the investigation of the changes of magnetisation which corre- 
spond to changes of magnetic force. For if /7= the grms. 
weight supported per square centimetre, 7 = the magnetic 
force, and 7 = the magnetisation, then for the divided ring 
We = 2nl? + H1; 
and by giving to W and H the values found to correspond, it 
becomes possible to find corresponding values of / and Z, 
These are contained in the first and third columns of the table. 
When // has exceeded about 200, the ratio of Z to Hno longer 
continues to diminish, and the curve expressing the relation 
between them apparently becomes a straight line. Were the 
experiment carried much further, a tendency to a limit would’ 
probably be indicated; but if there is one it must be con- 
siderably higher than it is generally believed to be. 
If & denote the susceptibility, « the permeability, and & the 
magnetic induction, then 7= 4H, w= 1 + 4nf, and B= pH. 
Hence the values of 2, uw, and # corresponding to different 
values of 7 can be found, and are given in the table. The 
figures in the last two columns are of great interest. Row- 
land, in order to exhibit the results of his well-known experi- 
ments in the form of a curve which (as he believed) would be of 
finite dimensions, plotted the values of » as ordinates against 
those of B as abscissee. The curve of m thus obtained, after 
reaching a maximum for B = 5000, fell rapidly and in an almost 
straight line towards the horizontal axis. Assuming that the 
line would continue to be straight until it actually met the axis, 
Rowland concluded that the maximum of magnetic induction 
was about 17,5C0 units. 
Now the greatest magnetic force used in Rowland’s experi- 
ments was only 64 C.G.S. units; the imaginary part of his 
curve, therefore, corresponds to values of // ranging from 64 to 
infinity. A part of this exceedingly wide gap is filled by the 
author’s experiments, in which 4 reaches 585 ; and if the values 
of « and # given in the table are plotted, the curve will be 
found (after a rapid descent) to ded vownd soon after the limit 
of Rowland’s observations, ultimately becoming, when B= 
RES 
current, a limit is soon reached beyond which’ the ratio of ; 19,8.0, almost parallel to the axis of B. 
