s - AD 
” Fesruary 3, 1923] 
















































separation of a precipi- 
nO,, and the rasan 
Illumination establishes a 
stationary state, KOH being simul- 
usly produced by the decomposition, and 
ed by combination with the colloidal MnO,. 
his involves an alteration of the P, of the solution, 
which causes the electrode potential changes. The 
decomposition is monomolecular over the range of 
concentrations investigated. The decomposition of 
i ified permanganate under identical conditions is 
zero order, due to non-formation of colloid. The 
hotoactive — tion lies in the ultra-violet merge 
tion spectrum of potassium ate, an e 
Hg line at 3128 AU is conden e chief agent. 
‘Th ¢ quantitative absorption of radiant ene is in 
agreement with the Einstein Law of Photochemical 
quivalent, a result of special interest as the first 
instance of its application to solutions.—E. A. 
Fisher: Some moisture relations of colloids. Pt. I. : 
' ag nba study of the rates of evaporation of 
water from wool, sand and clay. Curves obtained by 
plotting rates of evaporation against water contents 
are discontinuous. Each portion of the rate curve 
can be expressed by a simple type of equation con- 
necting rate of evaporation with water content. The 
rate curves obtained are similar in in the cases 
of wool (wholly colloidal with a cellular structure), 
qua sand (wholly non-colloidal with a granular 
Structure), silty soil (notoriously feeble in colloid 
] ies), and heavy clay sub-soil (typically colloidal 
viour). The so-called shrinkage of wool on 
drying is really a deformation and not a volume 
hrinkage. The absorption of water by wool is 
ttributed primarily to a filling up of fine pores of 
ious shapes and sizes; the vapour pressures of 
ool-water systems are determined by the diameters 
of the pores that are full of water.—R. Whytlaw-Gray, 
J. B. Speakman and J. H. P. Campbell: Smokes. 
I.: A study of their behaviour and a method of 
letermining the number of particles they contain. 
The smokes were produced (a) by the are discharge in 
air, (b) by volatilisation and condensation, (c) by 
chemical action. In each case highly dispersed 
systems of very minute particles were obtained. 
Examined in an ultra-microscope of the slit type, the 
life-history of a smoke falls into two main periods :— 
#) An unstable period in which the number of 
ticles diminishes rapidly with time. (b) A stable 
P in which the decrease in number is slow. 
During the first period the increase in size is very 
narked ; the changes are not due to evaporation but 
to a process of aggregation, which produces com- 
dlexes of different structure depending on the nature 
the dispersed substance.—R. Whytlaw-Gray and 
|. B. Speakman: Smokes. Pt. II.: A method of 
termining the size of the particles they contain. 
\ filtration method is used which enables the concen- 
ration in weight of the suspended solid matter in 
pidly changing smokes to determined with an 
uracy of about 3 per cent. A given volume of 
oke (usually x litre) is filtered through small tubes 
mtaining asbestos, and the increase in weight is 
scertained by a micro-balance sensitive to 0-0002 
n. Filtration takes about five minutes. Curves 
have been obtained showing the variation in weight 
concentration of the smoke over periods of 0-6 hours. 
Knowing the weight and the number of the particles 
h a given volume, the average mass of a smoke 
particle at different periods can be calculated and the 
_ growth followed quantitatively. Assuming the dens- 
ity of the particle to be that of the substance in bulk 
NO. 2779, VOL. t11] 
. 
lemica 
rn) 
' 
NATURE 
169 
the average radius can be evaluated. All the weight- 
concentration curves show an initial rise, and this 
fact, in conjunction with ultra-microscopic observa- 
tions, renders it probable that all these clouds contain 
in the early stages a large number of invisible particles 
of a microscopic size.—R. C. Ray: The effect of long 
grinding on quartz (silver sand). When quartz 
(silver sand) is ground for a long time the density of 
the ground substance is lower than the one which has 
not been subjected to grinding. The fall of density 
shows that as much as 25-7 per cent. of the material 
is converted from the crystalline to the vitreous 
condition. This value agrees fairly with that derived 
from the molecular heats of solution. 
Geological Society, January 10.—Prof. E. J. Gar- 
wood, vice-president, and afterwards, Prof. A. C. 
Seward, president, in the chair.—W. J. Sollas: Man 
and the ice-age. Four ancient coast-lines of remark- 
ably constant height have been traced around the 
Mediterranean Sea and along the western shores of 
the North Atlantic Ocean. hese, with their associ- 
ated sedimentary deposits, form the successive stages 
of the Quaternary system; namely, the Sicilian 
(coast-line about 100 metres) ; the Miazziati (coast- 
line about 60 m.) ; the Tyrrhenian (coast-line about 
30 m.) ; and the Monastirian (coast-line about 20 m.) 
The Sicilian deposits contain a characteristic cold 
fauna. The fauna of the Milazzian is warm-temperate 
and of the Tyrrhenian and Monastirian still warmer, 
The three lower coast-lines correspond with the three 
lower river-terraces of the Isser (Algeria), the Rhéne, 
and the Somme. Hence it may be inferred that the 
position of the river-terraces has been determined by 
the height of the sea-level. The climate of the 
Quaternary age was, on the whole, warm-temperate 
or genial, but interrupted by comparatively ‘short 
glacial intervals. It is now possible to assign the 
paleolithic stages of human industry to their place 
in the Quaternary system: thus the ‘‘ Strepyan "’ or 
pre-Chellean is Milazzian in age, the typical Chellean, 
Tyrrhenian, the evolved Chellean, Acheulean, and 
Lower Mousterian, early Monastirian, and the Upper 
Mousterian, Aurignacian, Solutrian, and Magdalenian, 
later Monastirian. The coast-lines of the Northern 
Hemisphere appear to have their counterparts in the 
Southern Hemisphere. The Quaternary movements 
are probably due to a general deformation of the 
globe involving eustatic changes in the level of the sea. 
Optical Society, January 11.—C. Davidson: On the 
amount of the displacement in gelatine films shown 
by precise measurements of stellar photographs. A 
stellar photograph consists of a number of minute 
discs scattered over an otherwise transparent plate. 
The purpose of the photograph is to determine with 
precision the relative positions of these discs. In the 
trigonometrical method of determining stellar paral- 
laxes photographs of a selected region are taken at 
two epochs about six months apart when the earth is 
at opposite sides of its orbit. A new star will show 
a displacement relatively to the distant stellar back- 
round. A series of such photographs give equations 
rom which the parallax and t-te motion are deter- 
mined. After the computed quantities have been 
taken out, each plate will show a small residual error 
made up of errors of measurement, observing, etc., 
and film displacement. From a discussion of many 
plates from Greenwich it appears that the average 
probable error of the measured position of a star on 
a single plate is +o-:0008 mm. Film displacement 
being only a part of the total it follows that this 
must be the upper limit of the probable error of film 
displacement. In the Kapteyn system of observa- 
tion, the photographs at the two epochs are taken on 
