May 7, 1885} 
In this chamber the air, which has been previously condensed 
and cooled, is allowed to deposit, in the form of snow, the 
moisture which it can no longer retain owing to the great diminu- 
tion of temperature due to expansion. George Punter, whose 
business it is to look after this snow chamber, rendered the most 
intelligent assistance in preparing the bars of ice, and in con- 
ducting the experiments. In this mode of experimentation the 
great variation of temperature, namely, between — 30° C., when 
the engines are stopped in the evening, and —12°C., as a 
maximum when they begin work in the morning is an unavoid- 
able drawback. Still, I think that the experiments, although 
they give uniformly negative results, are worth putting on 
record, 
Experiment 1.—A cylinder of ice was cast with a diameter of 
3 inches. 
experiment (NATURF, vol. v. p, 185), a wire loaded with a total 
weight of 5 lbs. It was left in the freezing-chamber 64 hours. 
No dent was traceable on the surface of the cylinder. 
Experiment 2.—W ith a similar cylinder and wire the load 
was increased to 1o lbs. and the time to 8 hours, with like 
negative results. 
Experiment 3.—With a similar cylinder and wire the load 
was further increased to 14 lbs. and the time to 173 hours, with the 
same result or absence of result. This experiment would seem 
to show that the ice refused to yield to a pressure of 20 to 30 
atmospheres, or probably more, applied in this way and for this 
time. 
Experiment 4.—A bar of ice 14 inches thick, 2} inches wide, 
and supported on bearers 134 inches apart, was left in the cham- 
ber from 12 n50n on Monday until 12 noon on Saturday. It 
showed no sign of bending under its own weight. 
Experiment 5.—A similar bar similarly supported was 
weighted in the middle with 7 lbs., and left for the same time. 
No sign of bending. 
Experiment 6.—A similar bar similarly supported was 
weighted with 18 Ibs., and left for the same time. There was 
no bending perceptible to the eye ; but, on removing the appa- 
ratus, the bar broke with the jar occasioned by setting it down 
somewhat carelessly, so that no exact measurement was taken. 
Experiment 7.—A bar of the same length and width, but 
thinner, tapering somewhat from { to 2 of an inch in thickness, 
was weighted with 7 Ibs., to which, during the last two days, 
seven additional pounds were added, and left for the same time. 
No bending by measurement. 
Such negative results are just what one would expect on 
theoretical grounds, and as an inference from previous experi- 
ments conducted at temperatures nearer the melting-point. But 
it is well not to rely on theory or on inference where direct 
experiment is practicable 
The matter, then, would appear to stand at present somewhat 
thus. The visco-ity of ice, due to whatever cause, is— 
(1) At temperatures at and above the melting-point...considerable. 
(2) i 3 below but near ts », ---much less. 
(3) ” ” between — 3°°5 C. and — 12° C....very slight. 
(4) op ee below - 12° C. bo ttl 
What seems now to be wanted is an experimental determina- 
tion of the lower temperature-limit of viscosity, which would 
appear to lie somewhere between ~12°C. and —3°'5 C., but 
probably nearer the latter temperature. 
University College, Bristol C. Ltoyp MorGAN 
BEN NEVIS 
At the meeting of the Royal Society of Edinburgh held on 
Monday last, Mr. John Murray, Vice-President, in the 
chair, Mr. R. T. Omond, Superintendent of the Meteorological 
Observatory on Ben Nevis, delivered, at the request of the 
Council, an address on two years’ residence and work there. 
Mr. Omond, at the outset, recalled the advantages which Ben 
Nevis presented as a high-level meteorological station, the 
services of Mr. Clement S. Wragge, and the chief steps that led 
up to the erection and equipment of the existing permanent 
observatory. Glancing at some of their daily experiences during 
last summer and autumn, he mentioned that some 3000 or 4000 
tourists climbed the mountain—sometimes at least 100 in a single 
afternoon. Since the middle of October, however, not more 
than half a dozen strangers had ventured up. Some came for 
information ; others were disappointed at finding they could not 
be fed as well as sheltered ; others came to spend the night, but 
were disappointed at finding they could not do so, Most of the 
Over it was hung, as in the well-known Bottomley | already succeeded in approximately establishing : (1) The normal 
NATURE 
17 
visitors, however, were satisfied, though a little astonished, by 
the explanation that the building on Ben Nevis was primarily a 
scientific observatory, and not a hotel. Storms of exceptional 
and terrific violence were described. Beautiful optical pheno- 
mena that had been witnessed, and the comparative scarcity of 
animal life on the mountain, were next alluded to. Rainbows 
are seldom seen. Thunderstorms are very rare. The tempera- 
tures during winter are not so low as many people think—ro° F. 
is about the lowest recorded as yet, and the ordinary winter 
temperatures ran from 15° to 25°. Observing that much must 
| yet be done in the work of the discussion and interpretation of 
the observations made on Ben Nevis, before the observa- 
tions could be safely used, he proceeded to state some 
of the more interesting points which Mr. Buchan had 
or average temperature and barometric pressure for each month, 
and the normal differences between these averages and those at 
sea-level. (2) The daily variation of temperature and pressure 
during each month. (3) The daily variation in the average 
velocity of the wind—this being shown to be greater at night 
than during the day, exactly the reverse of what holds good at 
sea-level. (4) Variations in the direction of the winds as com- 
pared with those prevalent over Scotland at any given time. A 
comparison of the Ben Nevis winds with those at low-level 
stations sometimes shows that both are part of one system, 
whether cyclonic or anti-cyclonic ; but the direction is almost 
always different, and in the case of cyclonic storms, coming from 
the west. The observed differences in direction seem to give 
an indication as to whether the storm centre is to pass to the 
north or south of Ben Nevis. If this point can be definitely 
made out, it will obviously be of immense value in forecasting 
weather. (5) The hygrometric observations indicate that the 
atmosphere on the Ben shows that during ordinary weather a 
state of persistent saturation, usually accompanied by fog 
or mist, prevails; but occasionally a sudden and _ extra- 
ordinary drought sets in, the temperature rises, and the 
sky clears, not merely of fog, but often of every vestige 
of cloud, and at the same time the valleys and lower 
hills are often shrouded in mist, showing that this dryness 
coming from above is not able to penetrate right down to the 
sea-level. The thorough investigation of these phenomena is 
one of the most important pieces of work connected with the 
Observatory, and may be expected to throw great light on the 
question of atmospheric circulation. (7) The rainfall of Ben 
Nevis is greatly in excess of what several theories of the distri»u- 
tion of rain led them to expect—a result possibly due to the 
great vertical movements of the atmosphere indicated by the 
hygrometric indications referred to above. Though there are 
many high-level stations in different parts of the world, none, 
perhaps, are so favourably situated as Ben Nevis for the investi- 
gation of what he had explained is the present great problem in 
meteorology, namely, the vertical movements of the atmosphere. 
If the Scottish Meteorological Society were possessed of suffi- 
cient funds to establish a completely-equipped observatory at the 
foot of Ben Nevis as well as on the summit, he was convinced 
that the science of meteorology would advance far more in a 
few years than it would by a generation of ordinary work with 
low-level] stations alone, 
SUNLIGHT AND THE EARTRA’S 
ATMOSPHERE* 
HERE is, we may remember, a passage in which Plato in- 
quires what would be the thoughts of a man who, having 
lived from infancy under the roof of a cavern, where the light 
outside was inferred only by its shadows, was brought for the 
first time into the full splendors of the sun. 
We may have enjoyed the metaphor without thinking that it 
has any physical application to ourselves who appear to have no 
roof over our heads, and to see the sun’s face daily ; while the 
fact is that if we do not see that we have a roof over our heads 
in our atmosphere, and do not think of it as one, it is because 
it seems so transparent and colourless. 
Now, I wish to ask your attention to-night to considerations 
in some degree novel, which appear to me to show that it is not 
transparent as it appears, and that this seeming colourlessness is 
a sort of delusion of our senses, owing to which we have never 
T Lecture delivered at the Royal Institution, April 17, 1885, by S. P. 
Langley. Communicated by the author. 
