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EETTERS TO THE EDITOR 
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Hypothetical High Tides 
WHATEVER conclusion may ultimately prevail with regard to 
the existence of very high tides in the earlier epochs of which 
geology has cognisance, | think that geologists will hardly accept 
the argument by Prof. Newberry, in your last issue (p. 357) as a 
settlement of the question, He appears to confound together 
three agents whose effects widely differ, viz. : (1) tidal waves of 
undulation, (2) tidal waves of translation, and (3) wind waves. 
In waves of undulation the particles of water move only ina 
vertical line, and can obviously neither denude nor transport. 
Waves of translation, acting as currents, are transporting agents, 
but are very subordinate to wind waves in their dennding power. 
In the present state of things waves of translation, z.e, the tides 
of our inland seas and estuaries, can hardly be said to~denude at 
all ; they simply shift mud and sand from place to place. Even 
if their speed were enormously increased, their effects, as 
denuding agents must still be very inferior to that of wind 
waves, 
The picture which Prof. Newberry has drawn of an enormous 
current rushing round and round the globe, sweeping away con- 
tinents, and destroying whole faunas, is not justified by fact. In 
the open ocean there would be no current at all due to tidal 
action, but simply, a vertical rise and fall, The Tr.lobites and 
Brachiopoda which swarmed in the Silurian seas would be 
conscious of no change in their surroundings save an alternate 
deepening and shallowing of the water over their heads. Where 
the tidal wave became inclosed between two Jands its height 
would increase ; but it would acquire no transporting power till 
it was filled up in narrow estuaries. Marine denudations would 
be mainly effected, as at the present day, by wind waves. 
I will present Prof. Newberry with a more energetic denud- 
ing agent than his tidal wave, viz. wind waves originating in the 
more powerful air currents of a globe rotating at (perhaps) thrice 
its present speed. But what could such waves do which our 
present waves cannot do? ‘They would simply work more 
rapidly. They would produce deposits of conglomerate, sand, 
and mud, which would in no respect differ from modern strata. 
There would be nothing in the nature of the sediments from 
which we could either affirm or deny the existence of a more 
potent engine of denudation, 
Prof. Newberry attempts to show that the hypothetical tidal 
wave of Devonian times would | revent the formation of coral- 
reefs. But this argument proceeds on the assumption that the 
habits of the Devonian corals were identical with those of recent 
reef-building polypes. Since, however, the Paleozoic corals 
belong to extinct families, any inference as to their habits must 
be purely hypothetical. Besides, the tidal wave must have 
greatly diminished by the Silurian or Devonian epoch, and may 
not have exceeded the 150 or 200 feet which Mr. C. Darwin 
fixes for the limit below which the polypes cannot live. 
Prof. Newberry makes a strong point of the evidences of 
quietude which we find in ancient littoral zones. The hypothetic 
tidal wave, he thinks, must have swept over the mollusks, corals, 
and sea-weeds which tenant the shore, so that they would be 
subject to the ‘‘ greatest mechanical violence,’’ and their zone 
would be rendered ‘‘ uninhabitab e.’’ To this I reply (1) that 
shores bordering on the open sea would only be exposed to a 
wave of undulation, and (2) that even a rushing waye of trans- 
lation would do less harm than our modern wind waves, which 
hammer against the shores where mollusks and sea-weeds manage 
to spend a tolerably peaceful life. 
There are other details on which I should like to join issue 
with Prof. Newberry, but I fear to trespass upon your valuable 
space. C. CALLAWAY 
Wellington, Salop, February 17 
SuRELY Mr. Newberry has too quickly come to the conclusion 
with which his paper of February 16 (‘* Hypothetical High 
Tides”) terminates. I think if he reconsiders the matter he will 
NATURE 
2 
3°5 
still find that there is room for discussion. Has he fully taken 
into consideration the fact that at present, although in seme 
places there are tides of thirty feet or more in height, notably 
where the waves roll in from the open ocean to some of the more 
or less confined bays or estuaries, on the contrary, in confined 
seas on the Mediterranean, Euxine, ard Baltic, the tide is 
scarcely perceptible? This being the case, is it satisfactorily 
proved that the old Potsdam beach of which Mr. Newberry 
speaks was not deposited on the shore of such an inland sea, 
where, in despite of the fact that the cceanic tides might measure 
2co feet or more, yet here I think the littoral zone might te 
comparatively quiet ; at any rate sufficiently so to support both 
animal and plant life? I merely make this suggestion in the 
hope that somebody more able to deal with the subject than L 
am will continue the discus-ion. A. HALE 
Filston Hall, Shoreham, Kent, February 20 
Rime Cloud observed in a Balloon 
UNDER this heading (NATURE, vol. xxv. p. 337) M. de 
Fonvielle made an interesting communication on a cloud sus- 
pended over Paris, through which he and M. Brissonet passed 
in a balloon on January 25 last. Its thickness did not exceed 
3co metres. ‘‘ The nebulous matter,” he says, ‘‘appeared per- 
fectly homogeneous, and I could see no trace of any crystalline 
matter, but an unexpected observation proved that it was formed 
of minute solidified atems of water in a real microscopic state of 
division.” 
While the balloon was floating over the cloud the sky was 
clear, and the temperature of the air from —2° to —3° C., and 
a rope hung from the balloon, the length of which was 60 
metres, its end being immersed in the cloud, ‘* We perceived 
that this part was quite loaded with hoar-frost, which had preci- 
pitated regularly by series of hairs a few millimetres long,” 
During the slow ascent no deposit of ice was visible ; ‘‘in cur 
descent, which was rather quicker, but not to a great degree, the 
sweeping may have accumulated the frost rime on the bottom of 
the car, which could nct have been easy to observe, and con- 
sequently I cannot state what occurred, but not a single crystal 
was deposited on our ropes during that period.” 
The mean temperature of the clcud is said to have been 5° 
C., but at the point at which the deposition of rime took place 
the temperature must have been 0° or lower, The upper layer 
of the cloud might have been colder than the layers below. 
it is improbable that the upper part of the cloud consisted of 
solid water, as no trace of any crystalline matter was visible. 
The smallest crystals of snow are visible in the air in the thin 
mists formed over channels of water, for the snow crystals 
glisten and reflect light from their exceedingly small surfaces. 
M. de Fonvielle must have observed this phenomenon, as ‘‘the 
sun was shining in its full glory.” It is more probable that the 
cloud was formed by small drops of liquid water cooled below 
zero. We know from Dufour’s observations that water-drops, if 
they are not in contact with solid matter, and floating in mixture 
of rock-oil and chloroform of equal density, may be cooled 
down to — 10° C., and even to — 20°C, if they are small enough, 
but become crystalline in contact with a solid body, especially a 
trace of ice. The hoar-frost which we nave frequently noticed 
this winter in Heidelberg, during hazy weather, and when the 
temperature was below 0°, may have been due to the solidi- 
fication of such drops of mist. It covered the plants first with 
filigree-like ice, and then with a thick crust of the same. In 
consequence of this, sometimes so much ice is deposited on the 
stems of the trees that great damage is cauved by it in the 
forests ; this was the case in the neighbcuring ‘‘ Rheinpfalz” in 
the winter 1858-59, and in other parts of Germany, especially in. 
Bohemia. 
It is, however, well known that a thick mist may consist of 
crystals of ice. Equally well known is Scoresby’s description of 
the ‘‘frost-dam” or ‘‘frost-rime ” of the Arctic regions, as it 
forms a layer inthe coldair over the warmer sea-water, the masts 
of the ships projecting overit. Mohn describes the ‘‘ Frostzdg,” 
which is formed in winter over the Norwegian fjords, which 
never freeze, when cold air, sometimes at a temperature of 20° 
C., and even lower, blows from the land over the water, which 
has a temperature aboye o° C. 
To these interesting occurrences of mist, generally termed ice- 
fog, one particularly interesting instance has been added by 
Hildebrand-Hildebrandsson’s meteorological observations made 
during the voyage of the Vega (Zeitschr, der Ocsterr. Gesellisch. f. 
