Sept. 15, 1870] 
moving. A moment's thought reminded me that a pool in such | 
a beach of loose pebbles was out of the question, and convinced | 
me that for the first time in my life I saw a Mirage. The hour 
proved to be exactly noon, Greenwich time. My friend, on hay- 
ing his attention called to it, saw a similar ‘* pool” on his terrace. 
On trying a series of experiments, we found that when we were 
quite erect the phenomenon was barely visible, and would never 
have commanded attention, but that as the eye was brought 
nearer and nearer to the surface the ‘‘ pool” grew larger and 
larger ; that in ordinary cases each observer could see it on his 
own terrace only, but that when he brought his eye to the outer 
edge of one terrace the ‘‘pools” on it and on that next below 
were visible at the same time, and were almost blended. As we 
advanced so did the Mirage. At 12.20, local time, when the 
sun was, of course, a very few degrees west of south, it bore N. 
33° W., magnetic variation being allowed for. The apparent 
water, like the real water in the adjacent sea, was a dark blue. 
We left the beach at two o’clock, and noted that the ‘‘ pools ” 
were as distinct as ever; and, being then some distance from 
Portland, we observed a similar phenomenon in that, the 
opposite, direction. 
Lamorna, Torquay, Sept. roth, 1870 
W. PENGELLY 
Extefnal Configuration of the Earth 
- Unper the heading of ‘‘ Volcanic Action 7, Denudation,” I 
observe in the last number of NATURE (Sept. 8th), a letter frotti 
Mr. A. H. Green, in which that gentleman finds fault with the 
conclusion arrived at in the following quotation, apparently ex- 
tfdeted fram some, to me unknown, report of my lecture on 
volcanoes, the original of whith is given in the Gevlogical Maga- 
sine for July 1870; in instituting ‘‘a comparison between the 
relative magnitude of the operations of internal and external 
forces in determining the main external fractures of our globe, we 
must grant the first rank to the internal, volcanic, or cataclysmic 
agencies, since, had it not bee#i for their operations, our globe 
would have remained without any visible land for the river to 
traverse, or the rain and ice to disintegrate and wear away ;”’ but 
as immediately afterwards Mr. Green himself adds, ‘‘ the latter 
part of this statement, cannot, of course, be called in question,” 
these very words, alone, seem to me tantamount to a complete 
admission that he can have no basis whatever for disputing the 
deduction that the internal agencies must be placed in the first 
rank; be it remembered, also, that his quotation is merely a 
summing up of the evidence brought forward in the course of the 
lecture. 
What I maintain—and I imagine every unbiassed person, 
whether scientific or not, if bit endowed with a reasonable 
amount of common sense, will agree with me,—is, that when 
eompating the relative importance of the two very opposite forees 
Which have combined to itiodel the external surface of our globe, 
in all times down to the preserit, the precedence must be given 
to that agency which is admittedly, not only the primary one, 
but also the one which actually called the other into existence. 
In answer to Mr. Green’s similes, and as he says that, in a 
tase like this ‘‘ it is hard to attach any definite meaning to the 
idea of rank,” I may assist him by simply asking, for example, 
whether any reasonable person, after contemplating, say St. Paul’s 
Cathedral, one of the most prominent features of our metropolis, 
could possibly think of ranking the architect who originated it 
below the stone-mason, or sculptor who, directed by him, after- 
wards altered so vastly the external appearance of the rough shell 
of the edifice as it first rose from the ground. 
Every one, whether geologist or not, admits that the most 
striking features in the world’s physical geography are the 
mountain ranges which rise up and look down upon the plains 
below, formed from their own dris ; and when it is remembered 
that these mountains are but so many grand proofs of the 
intensity and activity of those internal forces which not only 
elevated them, but, in most instances also, even supplied the 
larger portion of the rock substance which builds up their entire 
masses, does it not seem strange that any question of rank should 
arise, when comparing them with those external forces (denuda- 
tion, &c.) which, of very necessity, can only be great in propor- 
tion as the anterior internal forces developed the conditions 
necessary for calling them into existence, and provided materials 
for them to operate upon? 
Davip FORBES 
11, York Place, Portman »,1-, W-, Sept. 12th, 1870 | 
NATURE 
397 
The Meteor of 15th August 
In NATURE, page 357, you give notices and sketches of the 
Meteor of 15th August, and invite further description. 
The particulars stated by the Duke of Argyll, and specially 
the very exact location assigned to the Meteor by your Portrush 
correspondent, render it probable that a tolerable approximation 
may be made to the exact position as regards height, &c. : 
To this end, and in supplement of notice accompanying 
diagram second, NATURE, page 357, the following details are 
Important. 
The Meteor’s apparent position is recovered by means of its 
very. close proximity to snmmits of the Binn hill, near and to the 
north of this place, with assistance of the six-inch Ordnance 
maps. 
Local Time of first appearance 8'50 8°55 P.M. 15 Aug. 
Altitude, uncorrected for refraction, 7°35'25" 8°31'30" : 
Azimuth, west of north, 66°2'3 67°23'10" 
Observer's position, exactly in line of High-water level, 
In Latitude 56°3'51" North, Longitude 3°12’45" West. 
The apparent size of the Meteor partly explains these pairs of 
limits, within which the nucleus at least may be located. 
Gero, J. P. GRIEVE 
Kirkbank, Burntisland, Sept. 12th 
GEOLOGICAL DISCOVERY IN LIVERPOOL 
AE geologists visiting Liverpool for the approaching 
Meeting of the British Association for the advance- 
ment of Science will be glad to hear of the recent disco- 
very of some new beds in the coal measures near 
Liverpool, which are exceedingly prolific in fossil remains. 
The new line of railway between Liverpool and St. 
Helen’s runs at one place not far from Rainhill, through 
Thatto Heath, where along cutting was rendered neces- 
sary. This cutting is through beds all belonging to the 
carboniferous strata—a thick coal seam, and the accom-~ 
panying beds of shale and fireclay being all cut through. 
The fireclay contains abundant remains of all the varied 
plants of this epoch, witha few marine shells, Ax¢hrocosta 
in some places. There is a large collection of these 
fossils now on exhibition in the Derby Museum, collected 
by the Rev. H. H. Higgins, who has shown great energy 
in the matter, and who has most generously presented’ 
his collection tothe museum. This collection well merits 
the attention of all geologists, especially those interested 
in fe ssil botany. The plants found are in the most perfect 
state of preservation, and they are by no means difficult 
to meet with. They are chiefly Szg7llarza, Calamttes, 
Lepidodendron, Neuropteris Loshit, N. nervosa, and LV. 
gigantea: some of the species, the rarer Asterophyllites and 
Sphenophyllum, together with many others, being not yet 
accurately determired. Throughout the clay are found 
scattered rodules of ironstone, which, on being. broken 
up, are found to contain fossil remains, generally ferns or 
k#qiiseta. There haye, however, been two exceedingly 
valuable finds lately made, two fine specimens of the 
wings of Neuropterous insects having come tolight. One 
of these is in the possession of the Rev. H. H. Higgins ; 
and the other, measuring some 3 to 34 in. in-length, is in 
the possession of Mr. E. Cleminshaw, of Merton College; 
Oxferd. Both of these will be exhibited at the approaching 
mecting. They were both found in the ironstone nodules, 
and are very interesting, as only one other specimen, 
we believe, is known from the English coal measures. 
Not far from this cutting is a small coal pit, from which 
many interesting fossils are to be obtained. These are 
chiefly fish-remains, teeth, jaws, scales and bones, and a 
few rare ferns. The ease with which the blocks split into 
thin Jaminze render these fossils easily found, and they 
are in a good state of preservation. eel ee 
This locality is easily reached by train from Lime Street 
Station to Rainhill, from which place it is distant some 
twenty minutes’ walk, The navvies on the line are very 
obliging, and have all the finer specimens, with which 
they are very willing to part for a few coppers or sort 
tobacco, J. P, EARWAKER? 
oie 
