Feb. 23, 1871] 
NATURE 
327 

just outside the Straits, is natural ; and how far it may have been 
formed or increased by deposits left during the successive ages, 
hy this undercurrent of out-set-water, from the Mediterranean Sea 
into the Atlantic Ocean. Aw H: 
Jan. 19 
The Frost 
HAVING seen notices in your journal about the severity o! the 
late frost, I beg to state that its duration and severity have been 
most remarkable here, and unequalled, as far as my knowledge 
extends, for many years back. My instruments are standard ones, 
which have been recently compared at Kew, and placed in my 
garden quite detached from buildings, and facing the N.E. at 
4ft. elevation. I append a table of the observations, which may 
be interesting to some of your readers :-- 
Tec. Shade Sh-de Exposed Jan. Shade. Shade. Exposed. 
1870. max. min, min, 1871. max min. min 
20,0 Azo: ~ 30 30 To 27-5 198 18:2 
2 “30 Pass peal a> Be ez) 24 24 
2 OS™ 5 15 Be 33 Ae sheraitals 
23° 29 I'5 ° a. SE 14 13 
24 24 a2 a3 eesy) 23 23 
25. 25 +3 35S One AZZ, QT 31 
26 33 24 23 Vis) 30 29°5 
Ze at 24 Bas 8 40 28°3_28°3 
28 oz 27 27 9 40 2h gap con 
Bom 32.509 10:5 TO 10 40 28 28 
BOv SiG: T'S 14°5 Mis) 30 30°5. 29 
Sie -Szoe 152, - 14°3 12° 358 20%5)<\.20 
T3t Bron. 26"5 kn 26 
The frost was succeeded by a heavy gale of wind and a deluge 
of rain; in four days 2} inches fell, one inch being between 9 
A.M. 17th, and 9 A.M.on the 18th. This, together with the 
melting of the snow, inundated the valley of the Medway 
round us for miles. The greatest cold I ever registered here was 
on January 4, 1867, being 5° below zero. The highest shade 
temperature I have recorded was 100°'5 on July 22, 1868, 
which was the hottest summer ever experienced. 
‘Tunbridge G. H. FIe_pine 
Caves near St. Asaph 
Ir will interest archzeologists to know that new caves are 
being opened by Mr. Townshend Mainwaring in the neighbour- 
hood of St. Asaph, and that already we have much additional 
evidence brought to light as to the early inhabitants of that part 
of the country. In one which appears to run downward into 
the cliff at Carregwen, near Galltfeenan, remains of various 
animals have been found in brown cave-earth, among them 
one which has been determined to be that of a reindeer, by Mr. 
Dawkins, who is further of opinion that it has been gnawed by 
awolf or hyzna. This is very interesting, as the cave is high up 
in the face of a precipice, and with the present physical geography 
the larger animals could not get into that cave except by being 
carried there ; so that we have here either cave-earth containing 
remains of such a remote antiquity that the gorge below has 
been considerably altered since its accumulation, or we have the 
ancient abode of carnivorous beasts able to carry the large 
animals into their den. 
In Brysgill, Mr. Mainwaring has met with greater success. 
From the rubbish and tumble under the rock shelter outside the 
mouth of a large cave, he has obtained a fine bone scraper 
ground to a sharp edge, several flint flakes and bones of man, 
horse, ox, sheep, hog, &c. Inside the cave, immediately under 
the recent mould, there is a broken stalagmite floor, associated 
with which were human bones and the flint flakes, and cores. 
At about two feet below the broken stalagmite floor, the bones 
of a horse were found in undisturbed brown earth. Here we 
have evidently the home of some of our troglodytic ancestors 
who manufactured their flakes in the cave from flint which they 
may have procured from the drift not far off. 
This is only one of a number of most promising looking caves 
to which Mr. Dawkins some time ago called attention, and it is 
to be hoped that, with so many residents in the neighbourhood 
interested in scientific investigation! we may have them all 
systematically explored, and not lose any bit of important evidence 
from the want of observation at the time of discovery. 
T. McK. HuGHE: 


The Primary Colours 
ONE more proof that violet is a primary. Place a hand 
prism between the eye and the sunlight so as to show the pris- 
matic colours. ‘Then hold a sheet of yellow glass between the 
prism and the light, and observe the result. The reds and 
vellows are scarcely altered, the greens are very greatly intensi- 
fied, the blues and violets are altogether extinguished. ~ If violet 
had really any red in it, the yellow glass, which does not stop 
the red rays, would change the violet to red, or wouid show at 
least some ¢race of red where the violet had been. Instead of 
this, the violet is totally stopped out, and the space which. it 
occupied left dark. Wherever the secondary fs appears, this 
is changed to red by the stopping of the violet rays. The in- 
creased strength and brilliancy of the green shows clearly also 
the primary character of this colour. It is usually much 
weakened in the spectrum by mixture with the far-spreading 
violets ; when this is removed it comes out in full splendour. I 
commend this little experiment to amateurs ; it is simple and 
interesting. The same effect is produced by throwing the 
coloured spectrum on to a white wall, and holding the yellow 
glass between the prism and the wall. 
Leicester, Feb. 20 FREDERICK T. Motr 

Californian Oaks 
In Narure, No. 68, p. 313, you did me the honour to quote 
a paper of mine in reference to the edible qualities of some of the 
Californian oak acorns. You will, however, allow me to state 
that, though this is true of some species, such as Quercus lobata 
Nee, which was the one I chiefly referred to in the passage 
quoted, yet that the acorns of others have a decidedly injurious 
effect, or are inedible. For instance, it is very commonly believed 
by the zancheros that the acorns of Q. Kelloggti Newb. give rise 
among pigs to a peculiar disease of the kidneys, while the acorns 
of a new species from Southern Oregon—which I shall shortly 
describe in a work now in the press—(Q. echinoidées mihi) are so 
very bitter that no animal but the black bear ( Ursws A mericanus) 
will eat them, and it only when pressed by hunger. On the 
other hand the acorns of Quercus Orstediana (mihi), another as 
yet undescribed species, are so nutritious, that though the species 
never grows to a greater size than a small shrub, the produce of 
forty or fifty such bushes will fatten a hog. Again, there is a 
difference of quality among the edible species. ‘The ‘‘ digger” 
Indian, who is quite a covmotsseur in acorns, makes a difference ; 
for while the interior tribes prefer those of Q. /obata, those 
living near the coast chiefly affect Q. sonomensis Benth. Though 
pigs fatten freely on the acorns of Quercus Garryana Dougl., 
and in California on those of its ally, Q. Douglasit Hook., yet I 
never knew the Indians either in Vancouver Island or in Cali- 
fornia eat the acorns of either species, while those of Q. agrsfolia 
Nee, Q. chrysolepis Liebm., Q. densiflora Hook. and Arn., Q 
Sadlertana mihi (nondescript species), &c., are not, so far as I 
am aware, eaten by any animal but squirrels. The fruit of 
Castanopsis chrysophylla Doug., a plant allied to the oaks and 
chestnuts, is, however, in great favour with the black bear. I 
have eaten the acorns cooked in the manner described in the 
extract, and—I suppose in common with other naturalists in the 
less explored parts of North-west America—have been forced 
by hunger to search for the acorns which e/ carpentero (Melanerpes 
torquatus) stores away for its use in the spongy bark of Zorreya, 
Sequoia, Pinus, and various other trees, yet notwithstanding the 
sauce which famine gave to my appetite, I must confess that 
they were by no means palatable. This may, however, have 
been prejudice, for the Ancient Britons—who were by no means 
savages in the ordinary acceptation of the term—ate the acorns of 
Quercus robur, the common oak of this country. How they 
cooked them we are not informed. I presume, however, that it 
was not in so recherché a style as practised by some aboriginal 
friends of Mr. Paul Kane, the artist—a full description of which 
those curious in North American Indian cz/sive will find in that 
gentleman’s book descriptive of his journey across the American 
continent. RogertT Brown 
Edinburgh, Feb. 20 


THE ECLIPSE PHOTOGRAPHS 
qe accompanying woodcut is a copy of a drawing 
made from the negative No. 5, taken at Syracuse 
during the Eclipse of the sun on Dec. 22 last. When 
viewed by transmitted light, the negative shows chiefly 
the portions indicated by the unshaded parts, and the red 
