268 
NATURE 
[May 16, 1912 
LETTERS TO THE EDITOR. 
(The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications.] 
Clouds and Shadows. 
In Nature of April 18 Mr. Charles Tilden Smith 
described a cloud-like appearance which he considered 
was no cloud, as it remained quite stationary while 
stratus and small lower clouds were driven quickly 
across the sky. I think I can throw some light on 
the subject, as I observed a similar appearance both 
on April 5 and on April 8, the date of Mr. Smith’s 
observation. 
On April 5 I was observing pilot balloons when my 
attention was directed to a cloud which formed in 
the east; it was a cloud with very soft edges, which 
were constantly changing their shape and were fre- 
quently ripple-marked. I enclose a photograph of the 
cloud taken about 6 p.m. What chiefly attracted my 
attention was the fact that the cloud remained 
stationary, though it was obvious from the motion 
of the pilot balloons that there was a very strong 
wind in the upper air. The pilot balloon ascents at 
5-27 p-m. and at 6.24 p.m. showed that at one kilo- 
metre above the surface the velocity was 20 metres 
per second or more, which is fairly high for such a 
low level; the velocity fell off a little at greater 
heights, but it was 15 metres per second or so at 
three kilometres. 
As a north-west wind, which was the direction on 
this day, never seems to decrease very materially 
below the level of the stratosphere, it is obvious that 
the cloud in question was remaining stationary, 
though it was floating in a strong wind; presum- 
ably the particles of which it was composed were 
condensing on the windward side and evaporating on 
the leeward side of the cloud, as in cloud streamers 
seen round the peaks of mountains. That this was 
really the case I could not determine at the time, as 
I was taking observations of balloons, but on April 8 
I noticed very similar clouds shortly before sunset, 
and by watching them carefully it was quite clear 
that in this case the above supposition was correct. 
There was a great development of these soft-edged 
clouds just before sunset; they were arranged more 
or less in parallel bands, with a vanishing point in 
the south-west; the particles of which they were 
NO. 2220, VOL. 89] 
composed were coming from the north-west. At one 
time I noticed that the edges of one cloud broke up 
into ripple clouds which moved rapidly from the 
north-west until they reached another cloud into which 
they merged. 
If Dr. W. N. Shaw’s supposition is correct that 
changes of pressure in the lower layers of the atmo- 
| sphere are caused very largely by changes which 
occur in the level just below the stratosphere, it 
follows that a diminution of pressure at this level 
_will cause a decrease of pressure through the whole 
| crests. 
of the underlying layers, and, as Dr. Shaw has 
pointed out, condensation and formation of cloud may 
take place wherever there happens to be a damp 
_ layer, and we get, what is so often seen, the simul- 
taneous formation of sheets of cloud at widely 
different levels. 
On April 5 there was a great development of cloud at 
different layers at sunset. If at any particular layer 
condensation is almost taking place, any uplift of 
air will hasten it, and any wave motion that may 
exist will become visible by condensation in the wave 
On April 5 the strong wind passing over 
the irregularities of the surface, such as the South 
Downs in this neighbourhood, might have caused 
local uplifts of air which might have extended to con- 
siderable heights; thus at some particular layer 
condensation might take place, the cloud particles 
forming where the air was rising and evaporating 
further to leeward, where the air was descending. 
Soft-edged clouds, 
way, may sometimes be seen covering the tops of the 
Downs and closely following their contours, giving 
the hills a strange appearance of increased height, 
as recorded by Richard Jefferies in ‘‘Wild Life in a 
Southern County.” 
It is difficult to estimate the heights of the clouds 
seen on April 5 and 8, but I think, though I am not 
quite sure, that I saw a pilot balloon projected on 
one of them when it,was at a height of about three 
kilometres; if this were so, the clouds must have 
been at a greater height. 
Cuartes J. P. Cave. 
Ditcham Park, Petersfield, May 5. 
Mammalian Remains at the Base of the Chalky 
Boulder Clay Formation in Suffolk. 
Mr. E. P. Riptey, Mr. Frank Woolnough, curator 
of Ipswich Museum, Mr. Fredk. Canton, and myself 
have to-day assisted in the removal of a large curved 
tusk which was found at the base of the chalky 
boulder clay formation, and on the top of the under- 
lying middle glacial sand, at a depth of 11 ft. 3 in. 
from the present surface of the ground. 
Numerous pieces of bone evidently belonging to the 
same animal have been found lying near the tusk, 
but were removed before we arrived. The spot 
where this discovery has been made is in a shallow 
valley at Charsfield, a village about eleven miles 
north of Ipswich, and it is owing to the kindness of 
Mr. W. H. Youngman that I was apprised of the 
find. 
This shallow valley is a typical example of the dry 
valleys so often met with in Suffolk and elsewhere, 
and is not apparently connected with any present 
river system. 
The section in the small pit, which is being worked 
for stone, shows 1 ft. of surface humus, 3 ft. of 
blackish gravel, 4 ft. of chalky boulder clay, develop- 
ing into, and evidently a part of, a loamy gravel 
about 3 ft. in thickness. 
At the bottom of the section the fine, stoneless 
middle glacial sand is exposed. The accompanying 
formed in a somewhat similar — 
ine” 
