262 
NATURE 
[JuLy 10, 1902 
SOCIETIES AND ACADEMIES. 
LONDON. 
Royal Society, May 15.—‘‘ A Note on the Recrystallisation 
of Platinum.” By Walter Rosenhain, B.A. (Cantab.), B.C.E. 
(Melbourne). Communicated by Prof. Ewing, F.R.S. 
The author has observed phenomena in platinum analogous to 
those of recrystallisation in other metals previously described 
by Prof. Ewing and himself (Pz, 7vans. A. 1900, vol. cxcv.). 
It is well known that platinum which has received a prolonged 
exposure to high temperature becomes brittle and that its surface, 
if it has been exposed to flame, shows crystalline markings. 
This has been ascribed to the action of carbon, but the author 
ascribes it to a process of recrystallisation and subsequent surface 
etching by the fame. Evidence in favour of this view is drawn 
from the micro-structure of this ‘‘ brittle” platinum, from its 
behaviour on etching with aqua-regia, and from its mode of 
fracture when hot. The micro-structure is shown to be that 
characteristic of recrystallised metals, the action of aqua-regia is 
found to brighten the flame-etched surface, and the fracture 
follows lines characteristic of the surface crystals, thus proving 
that the surface pattern truly represents the structure of the 
whole thickness of metal. The author points out that cold- 
worked metal is very apt to undergo recrystallisation at high 
temperatures, and that in several well-known cases brittleness 
results from such a process; he _ believes, therefore, that 
recrystallisation accounts for all the phenomena except the 
sur/ace markings, and these he ascribes to an etching action of the 
flame in which the temporary formation of a carbide may play a 
part. 
June 19.—‘‘On an Approximate Solution for the Bending 
of a Beam of Rectangular Cross-section under any System of 
Load, with Special Reference to Points of Concentrated or 
Discontinuous Loading.” By L. N. G. Filon, B.A. (Cantab.), 
M.A., B.Sc. (Lond.), King’s College, Cambridge, Fellow of 
University College, London, and 1851 Exhibition Science 
Rah Scholar. Communicated by Prof. G. H. Darwin, 
BSR:S: 
The paper investigates the elastic equilibrium of a long bar 
of rectangular cross-section in cases where the problem may be 
treated as one of two dimensions, the plane of the strain being 
the vertical plane through the axis of the bar. 
General solutions in arbitrary functions are first obtained. 
These, on being applied to the particular case, lead to series 
involving hyperbolic sines and cosines. These series, when the 
length of the bar is made infinite, degenerate into integrals 
which can be expanded in ascending powers of the radius vector 
from any point, within a certain circle of convergence. The 
properties of these series and integrals in the neighbourhood 
of points of concentrated or discontinuous load are specially 
considered. 
By means of these solutions, arbitrary conditions of stress 
over the top and bottom faces of the beam can be satisfied. 
Various cases, including those of a doubly supported beam 
carrying a central isolated load, of a block resting upon a smooth 
rigid plane and pressed by a knife edge on its upper surface, of 
a beam under two equal opposite loads not in the same straight 
line, and of a bar under tension produced by knife-edge “ grips” 
on either side, are considered. 
The corrections that must be applied to the expressions given 
by de Saint Venant for stresses in the free parts of long bars, 
when we approach the points of application of concentrated 
loads, are investigated at length. It is found that, at distances 
fiom the sections where such load is applied of the order of the 
larger diameter of the cross-section, these corrections, z.e. the 
local perturbations, become insensible. 
Finally, solutions in finite terms are discussed, and such a 
solution is obtained for a beam carrying a uniform load. 
Physical Society, June 20.—Prof. S. P. Thompson, 
president, in the chair.—Mr. G. F. Herbert-Smith exhibited 
the three-circle goniometer recently constructed for the British 
Museum from his designs. In this form of goniometer the 
advantages of the earlier forms are combined : as with the two- 
circle or theodolite goniometer, a crystal is only once adjusted 
during the whole of the observations, and as with the one-circle 
goniometer observations are made in zones, and full advantage 
may be taken of the zonal characters of crystals and of the 
simple formulce depending thereon.—A paper on the heat evolved 
or absorbed when a liquid is brought. in contact with a finely 
NO. 1706, VOL. 66] 
divided solid, was read by Mr. G. J. Parks. Pouillet discovered 
the fact that when a powder is put into a liquid which does not 
exert any solvent or chemical action upon it, there is, in general, 
a rise of temperature. The objects of the present investigation 
were to obtain a relation between the quantity of heat evolved 
and the area of the surface exposed, to find the rate of variation 
of heat evolved with temperature, and to apply to the results the 
laws of thermodynamics. From the results of his experiments 
the author states that when silica, sand or glass is brought into 
contact with water at approximately constant temperature, the 
heat evolved is proportional to the area of the surface exposed 
by the solid, and the amount of heat developed per square 
centimetre is approximately ‘00105 calorie when the temperature 
isnear 7°C. Assuming that the phenomenon of Pouillet is 
reversible, and that it is due to a pressure at the surface of the 
powder, the author has, by the application of the laws of 
thermodynamics and the results of his experiments, arrived at 
the conclusion that at 7° C. the surface-pressure of water and 
silica diminishes at the rate of 157 dynes per centimetre for an 
increase of temperature of 1°C. Experiments made at different 
temperatures indicate that the heat evolved is roughly propor- 
tional to the absolute temperature. Experiments were also made 
which showed a fall of temperature on putting a finely divided 
solid into mercury.—A paper by Prof. R. W. Wood, on a 
remarkable case of uneven distribution of light in a diffraction 
grating spectrum, was read by the Secretary. It is a well-known 
fact that in the spectra formed by diffraction-gratings the light is 
unevenly distributed, that is, the total light in any one spectrum 
will not recombine to form white light. The author has 
been examining a most remarkable grating in which the drop 
from maximum illumination to minimum occurs within a range 
of wave-lengths not greater than the distance between the sodium- 
lines. In other words, the grating at a certain angle of 
incidence will show one of the D lines, and not the other. 
Experiments with polarised light have proved that these 
anomalies are only exhibited when the direction of vibration 
(electric vector) is at right angles to the ruling. The paper 
gives a detailed account of the appearance of the spectra at 
different angles of incidence when the grating is in air and when 
it is immersed in different liquids. It is shown that the 
phenomena are not due to interference between disturbances 
coming from widely separated lines, and the author suggests that 
the matter must be referred to the form of the groove.—A paper 
by Prof. R. W. Wood, on the electrical resonance of metal 
particles for light waves (second communication), was read by the 
Secretary. In a previous paper the author has shown that 
granular deposits of the alkali metals exhibit brilliant colours by 
transmitted light. These colours were referred provisionally to 
the electrical resonance of the minute particles for light waves. 
The present paper gives an account of experiments made with gold 
and silver films to determine whether the resonance is molecular, 
or whether it is an electrical vibration of metallic masses, smaller 
than the light waves, though of the same order of magnitude. 
Further investigations on the dispersion of the films and a more 
careful study with polarised light will doubtless throw light on the 
matter.—Prof. H. L. Callendar showed a simple apparatus for 
measuring the mechanical equivalent of heat. 
Royal Microscopical Society, June 18.—Dr. Henry 
Woodward, F.R.S., president, in the chair.—The secretary 
read a note from Mr. Nelson on some high-power photo- 
micrographs of Pleurosigma angulatum, Surivella gemma and 
Coscinodiscus asteromphalus, taken by Mr. F. E. Ives.—Mr. A. 
Hilger exhibited a new photo-measuring micrometer attached to 
a microscope designed specially for accurately measuring the 
distances between the lines of the spectrum, but it could also 
be used for various laboratory purposes.—Messrs. Watson and 
Sons exhibited and described a new two-speed fine adjustment 
for microscopes. They also exhibited a microscope fitted with 
a new holder by which metallurgical specimens could be held 
in any position while under examination.—Messrs. Carl Zeiss 
exhibited their epidiascope, a projection apparatus by means of 
which large brilliantly illuminated pictures of objects can be 
shown on a screen. Objects such as ordinary lantern slides and 
transparencies up to 9 inches square, opaque objects, such as 
photographs, drawings, prints, bones, medals, butterflies in their 
natural colours, \c., were shown in illustration of its capa- 
bilities. A simplified form of microscope was then attached to 
the instrument, and micro-slides were projected on the screen, 
giving pictures about 6 feet diameter, with great brilliancy and 
sharpness of definition.—Prof. Marcus Hartog gave a short 
