A VALUABLE WORK ON MINERALOGY BY THOMSON. 
173 
MR. JOHNSON iOF QUEEN’S, 
READ A SHORT ACCOUNT OF 
SOME MATHEMATICAL RESEAR- 
CHES HE HAD LATELY PUR- 
SUED ON OPTICAL IMAGES.-He was 
led to this remarkable result, that, according to 
the mathematical theory, the image of astraight 
line placed vertically in water, and also 
horizontally, are each the loci of equations of 
high dimensions and great complexity, and 
should be curves of high orders, but to the 
eye they are straight lines ; a very accurate 
construction of the curves, however, shewed 
that certain portions of them (which properly 
represent the image) will approach so near 
to straight lines as to be such to the eye. 
Drawings of these curves were exhibited. 
MR. POWELL GAVE A COMMUNE 
CATION ON THE DISPERSION OF 
LIGH r. — In continuation of former papers, 
in which he illustrated the subject by dia- 
grams of the several spectra formed by prisms 
of water, oil of turpentine, flint glass, oil of 
cassia, oil of aniseed, andsulphuret of carbon, 
shewing their comparative refiactive and dis- 
persive powers. 
DR. BUCKLAND READ A FUR- 
THER STATEMENT RELATIVE TO 
'J HE LUMINOUS APPEARANCE ON 
THE FLOWERS OF THECENO 1 HERA 
MENTIONED AT THE LASTMEEtI 
ING.— It wasj distinctly stated that the 
luminous appearance continued uninterrupt- 
edly for a considerable length of time ; it did 
not appear to resemble any electric effect: 
and the opinion which seemed most probable 
was, that the plant, like many known instan- 
ces, has a power of absorbing light, and 
giving it out under peculiar circumstances. 
DR. DAUBENY EXHIBITED SOME 
SPECIMENS OF SAND AND CLAY 
FOUND IN THE BOTTOM OF THE 
CAVERNS.— In limestone, at Michell’s 
town, near Cork. The sand covered the 
feottom of the cave to an unknown depth, and 
was itself covered with a crust of stalagmite. 
The sand must have been washed in through 
a very narrow entrance; and there is no 
existing stream capable of so introducing it. 
No bones or other remains were found in it. 
Dr. Buckland also explained the occur- 
rence of such sand, &c. by diluvial action, 
and proceeded to remark a curious circum- 
stance connected with these caverns. There 
has never been an instance in which any 
deposits have taken place at the bottoms of 
caves, except such as are composed of recent 
remains, and the mud, sand, &c. of the sur- 
face; debris and fossil remains of older for- 
mations never occur in them. The only 
instance known of any older remains in 
caverns, is that of the caves at Palermo, 
belonging to the latertertiary period, and 
containing shells, &c. of that formation per- 
forated by pholades, though now raised 300 
feet above the sea. 
Dr. Buckland also observed that the origin 
of caves in limestone had during many years 
occupied his attention, and has always been 
considered by him one of the most difficult 
problems in geology. To a certain degree 
they have in many cases been the effects of 
mechanical violence producing lateral move- 
ments, and tearing asunder portions of solid 
rocks, during the elevation, or subsidence, of 
the strata in which they occur. In cases of 
this kind, the fractures are usually rectilinear, 
and partake of the nature of a slip or fault, 
never filled up. But the lateral enlarge- 
ments and tubular communications that pro* 
ceed in various directions from the main aper- 
tures, and the vaulted anddorae-shaped expan- 
sions that occur at irregular intervals along 
the minor winding passages, cannot be refer- 
red to mechanical violence ; and an adequate 
cause of their origin may possibly be found 
in the influence of acid vapours, (probably 
carbonic acid,) rising through fractures 
adjacent to these corroded portions of the 
limestone. 
Caverns in solid limestone could not have 
been produced, like cells and cavities of 
various size in beds of porous lava, by air 
included in the viscid substance of the strata, 
before or daring the progress of consolidation, 
because they are most abundant in limestones 
of the most compact character, and in which 
no other trace of cellular structure is to be 
found. Moreover, the interior of caverns 
usually presents an irregular carious surface, 
similar to that which is produced on a mass 
of limestone submitted to the action of an 
acid. 
If these supposed acids were mixed with 
water, the lime thus dissolved would have 
been removed in a state of solution, and the 
sides of the caves would be found studded 
with the less soluble contents of the strata, 
such as siliceous concretions, and fragments 
of orgainic remains, standing in relief, as we 
often see them around the interior of these 
carious vaultings. 
The organic remains in these strata, parti- 
cularly the corals, are often disposed in such 
a manner as to shew that considerable time 
elapsed during the deposition of the succes- 
sive beds of limestone in which they are enve- 
loped ; no accumulations of gas in connected 
cavernous expansions passing from one 
stratum into anotlier could have taken place 
in beds of limestone thus deposited at succes- 
sive intervals. 
Dr. Daubeny expressed a doubt as to 
whether all caverns could be accounted for 
by aqueous corrosion alone, and conceived 
that the large vaulted chambers into which 
many of them suddenly expand, may have 
been originally produced by an evolution of 
gaseous matter, whilst the rock itself was in a 
softened condition. 
OUTLINES OF MINERALOGY, GE- 
OLOGY, AND MINERAL ANA- 
LYSIS. 
By J'homas Thomson, M. D., F. R. S., &c. 
2 vols. Londov, l836. 
There is not any more important result 
which has emanated from the discovery of 
the atomic theory than the demonstration that 
the mineral kingdom consists, not of a multi- 
tude of heterogeneous bodies, heaped toge- 
