f 
May 20, 1886] 
syes follow in such rapid succession that the impression made by 
me flash does not diminish sensibly before the next flash on the 
ame eye is received. The number of flashes for each eye which 
required to produce an apparently continuous view, without any 
lickering effect, is from thirty to forty per second. As the disks 
we SO cut as to produce two flashes for the right eyes and two for 
he left in one revolution, they must consequently be kept rotating 
it a rate of from fifteen to twenty revolutions per second. 
‘The rotation of the disks is effected by a driving-wheel and 
yand worked by a crank handle at the back of the apparatus. 
_ The perspective effect obtained by the above arrangement is 
ery perfect, the image of each object standing out in solid 
elief. 
‘Considering that by this arrangement the two eyes never 
ee at the same time, and that each eye views its picture 
fter the other, it is interesting to find that the persistence of 
ision so completely bridges over the alternate interruptions to 
which it is subjected as to produce the effect of a continuous 
‘jew. 
‘The advantages claimed for this form of stereoscope are: that 
he pictures can be enlarged to such an extent as to appear equal 
or even larger than the original objects from which they were 
aken ; and that the eyes in looking at the pictures are not in any 
yay subjected to strain by lenses, prisms, or reflectors, or by the 
lifficulty which some persons experience in getting the two pictures 
9 superpose. For each eye views its corresponding picture in 
xactly the same position it would see it in if it were looking at 
he original, since the two pictures are practically in the same 
lace, which is not the case in any other form of stereoscope. 
Although with the apparatus as here described only two persons 
an see the pictures at the same time, it would not be very difficult 
onsract it so as to be available for a greater number. The 
ide disks above described only serve to control one pair of eye- 
oles each, but by making them larger they would serve for two 
airs each, thus accommodating four observers. By increasing 
he number of disks, the number of observers might be increased 
roportionately. 
May 6.—‘‘The Influence of Stress and Strain on the Physi- 
al Properties of Matter. Part I. Elasticity (continued). The 
tffect of Change of Temperature on the Internal Friction and 
Torsional Elasticity of Metals.” By Herbert Tomlinson, B.A. 
‘ommunicated by Prof. W. Grylls Adams, M.A., F.R.S. 
' The author has recently had the honour of presenting to the 
society a memoir relating to the internal friction of metals when 
ibrating torsionally at temperatures ranging from o° C. to 
5 C. He now brings forward results’ which have been ob- 
peed in experiments on the effect of change of temperature on 
ae torsional elasticity and internal friction of metals. The 
\pparatus used and the mode of experimenting are fully described 
ithe paper, so that it will be sufficient, perhaps, to state here 
nat the vibration-period and the logarithmic decrement were 
ery carefully determined at four different temperatures between 
*C. and too C., and that the formule were worked out 
ee method of least squares. These formule were given in 
wbles. 
‘From a consideration of the tables it may be gathered that :— 
(d) The torsional elasticity of all metals is temporarily de- 
reased by rise of temperature between the limits of 0° C. and 
50° C., the amount of decrease per degree rise of temperature 
icreasing with the temperature. To this may be added that 
ie percentage decrease of torsional elasticity produced by a 
en rise of temperature is for most metals about twenty times 
te corresponding percentage increase of length. 
) If we start with a sufficiently low temperature the internal 
ion of all annealed metals is first temporarily decreased by 
of temperature and afterwards increased. The temperature 
minimum internal friction is for most annealed metals 
ween o° C, and 100° C. ; for most hard drawn wire, how- 
e the temperature of minimum internal friction is below 
(f) The temporary change, whether of the nature of increase 
‘decrease, wrought by alteration of temperature in the internal 
| tection of metals, is in most cases enormously greater than the 
responding change in the torsional elasticity. 
‘Linnean Society, May 6.—Sir John Lubbock, Bart., 
resident, in the chair.—Prof. H. Marshall Ward was elected a 
low of the Society.—Mr. D. Morris exhibited a number of 
‘ng beetles (Pyrophorus noctilucus) from the island of 
ominica. These had been fed on sugar-cane during the voyage 
i 
INWAT Cie 
69 
to England. On the meeting-room being darkened, the phos- 
phorescent show of light emitted by the insects was very 
brilliant. —Dr. Chas. Cogswell drew attention to framed water- 
colour drawings of Lettsomia ageregata and Fothergilla gardeni, 
botanical mementos of the two distinguished physicians Lettsom 
and Fothergill.—Sir J. Lubbock’s paper on forms of seedlings 
was, by request, adjourned, so as to give opportunity for discussion 
of Mr. Romanes’s communication.—Mr. G. J. Romanes then 
read his paper on physiological selection : an additional sugges- 
tion on the origin of species. A full account of this paper will 
appear in a future number.—Thereafter the two following 
papers were read in abstract :—Descriptions of new species of 
Galerucidz, by Joseph S. Baly.—On some new species of the 
genus Metzgeria, by Wm. Mitten. 
Geological Society, April 21.—Prof. J. W. Judd, F.R.S., 
President, in the chair.—Henry Fisher, Frederick Edwin Har- 
man, Henry Johnson, Edward Alloway Pankhurst, and Henry 
Woolcock were elected Fellows of the Society.—The following 
communications were read :—On a certain fossiliferous pebble- 
band in the ‘‘ Olive group” of the eastern Salt Range, Punjab, 
by A. B. Wynne, F.G.S. The principal object of this paper 
was to oppose the views recently published by Dr. Waagen as 
to the age of certain Boulder-beds in the Salt Range of the 
Punjab. By that author these beds had been considered con- 
temporaneous with each other, and assigned to the epoch of the 
Coal-measures, in consequence of the discovery by Dr H. 
Warth of Carboniferous fossils, especially Australian forms of 
Conularia, in nodules restricted to a particular layer in the upper 
part of a Boulder-bed in the eastern Salt Range. Mr. Wynne 
adduced evidence to show that the fossils in question occur, not 
in concretions, as supposed by Dr. Waagen, but in pebbles 
evidently derived from an older series ; and consequently there 
was no proof that the Boulder-bed in question was older than 
the Cretaceous Olive-beds with which it had hitherto been as: o- 
ciated. The principal Boulder-beds in the Salt Range were 
then briefly noticed ; those beneath the Carboniferous Limestone 
west of the Indus, those near Amb and Sakesir peak, associated 
with the “purple sandstone,” ‘* Obolus-beds,” and ‘‘ speckled 
sandstone,” and those in the eastern portion of the Salt Range, 
amongst the beds of the ‘‘ Salt pseudomorph zone” and ‘‘ Olive 
group” being successively passed in review, and their relations 
to overlying and underlying strata explained. It was shown that 
Boulder-beds and conglomerates containing pebbles and boul- 
ders of the same crystalline rocks are not confined to one horizon. 
In conclusion, the resemblance of the rock, of which the pebbles 
containing Conulariz, &c., were formed, to that forming some 
of the ‘‘ magnesian sandstone ” and ‘* Obolus-beds ” was pointed 
out, and it was suggested that the pebbles in question may have 
been derived from representatives of those beds formerly exist- 
ing to the southward.—On the phosphatic beds in the neigh- 
bourhood of Mons, by M. F. L. Cornet, For.Corr.G.S. These 
beds are situate in the province of Hainaut, near the town of 
Mons (Belgium); the workings have increased of late years, 
and in 1884 yielded 85,000 tons of phosphate. They occur in 
the Upper Cretaceous, which is exceptionally well developed in 
the district, filling a troughin the Carboniferous rocks, and itself 
denuded for the reception of Tertiary and Quaternary beds. 
Omitting all Cretaceous groups below the middle of the fifth 
stage, the following is the sequence of the Cretaceous beds 
which contain the phosphatic series :—C. Tufaceous chalk of 
Ciply, with the Poudingue de la Malogne at its base. D. Brown 
phosphatic chalk of Ciply. E. Coarse chalk of Spiennes. F. 
White chalk of Nouvelles. F is a pure white chalk with some 
flints, and contains Belemnitella mucronata, Rhynchonella 
octoplicata, Terebratula carnea, Ananchyt:s ovatus, &c.,—an 
horizon well known throughout North-Western Europe. Series 
E and D represent one geological horizon characterised by 
Ostrzeze, Brachiopoda, &c., in great numbers, but also contain- 
ing Belemnitella mucronata, and lying between two distinct 
planes of erosion. The brown phosphatic chalk (D), which 
forms the upper division of the series, is about 70 feet thick, 
and may be described as consisting of three parts ; the upper is 
tolerably pure carbonate of lime, but in its lower portion be- 
comes charged with brown granules mainly consisting of phos- 
phate of lime ; these continue to increase towards the central 
or main phosphatic mass, which is also highly fossiliferous in 
places. This central portion constitutes the main phosphatic 
beds, but the amount of phosphoric acid (dry) is not more than 
12 per cent, Hence, it is necessary to increase the richness in 
phosphate of the deposit in order that it may be available for 
