146 
NATURE 
[ Dec. 2, 1869 
The simplest method of all was the employment of a series of 
different angles suited to the altitude of the object ; but as this 
has some inconveniences Mr. Simms suggested the employment 
of an adjustable prism, as, for example, adjustable tilting of the 
field-glass ,of the eye-piece. This method, though simple, intro- 
duced undesirable optical effects. It appeared necessary, there- 
fore, that the correction should Le effected outside the eye-piece ; 
and the best method seemed to be the combination of a con- 
yexo-concavye and a convexo-plane lens, the convexity of the 
latter fitting into the concavity of the former, and admitting of 
being rotated within it, so as to vary the corrective effect accord- 
ing to the state of the air or the position of the object observed. 
Mr. Cayley, F.R.S., afterwards noticed that the desired effect 
could be secured by combination of two prisms, in one of which 
there is a convex, and in the other a concave cylindrical surface 
of the same curvature ; when these cylindrical surfaces are made 
to rotate on each other, the opposite faces of the combination 
can assume any relative position between parallelism and an in- 
clination equal to the sum of the refracting angles of the com- 
ponent prisms. Both contrivances are described in Brewster's 
Optics ; and it is satisfactory to consider that the troublesome 
effect of atmospheric chromatic dispersion can be corrected 
effectually by contrivances so well known.—The Astronomer- 
Royal then invited the attention of the meeting to a proposition 
which had been made by the American observers, that the 
passage of Venus over the solar chromosphere should be ob- 
served by spectroscopists during the transit of 1874, for the pur- 
pose of determining the solar parallax. Mr. Huggins described 
the methods of observation available for the purpose. Mr. 
Proctor expressed doubts .as to the accuracy of the suggested 
method, remarking that the phenomenon, to be observed to the 
best advantage, would require other stations than those selected 
for observing internal contacts, and that the effect of parallax, 
by causing Venus to cross different parts of the chromosphere, as 
seen from different stations, would be a fatal objection, since we 
have no reason for believing that the chromosphere is uniformly 
deep. He remarked also that we are not merely ignorant of the 
exact point at which Venus will cross the sun’s limb, but of the 
angle at which her path will be inclined to the limb, Mr. Stone 
intimated his belief that we should find a number of difficulties 
cropping up around the new method, which might render obser- 
vations as unsatisfactory as those made in 1769 upon the internal 
contact.—After some remarks by the Chairman upon the advan- 
tages of applying photography to the coming transits, a paper by 
Mr. Alexander Herschel, on the November meteors, was read to 
the meeting. Mr. Herschel shows that there is evidence of a 
triplicity in the meteoric stream, since in 1868 three distinct 
maxima were observed in England, America, and China. In 
1867 and 1866 also, three maxima were observed, but they were 
not separated by so wide an interval.—Mr. Proctor then read a 
paper on the application of photography to the transit of 1874. 
The paper was illustrated by a chart exhibiting the passage of 
the earth through the shadow-cone of Venus, and showing along 
what lines stations should be placed, at any time, so that the 
relative displacement of Venus might be along a radial line of 
the sun’s disk. By so selecting stations (or times) he remarked, 
the whole question would become simply one of parallax, no 
appreciable error would come in through misplacement of the 
fiducial cross-lines, and so photography would do the best work 
it was capable of, for determining the sun’s distance. In reply to 
Mr. Proctor’s comments on the importance of the coming transits, 
Mr. Stone pointed out the close correspondence of the results he 
has deduced from the observations in 1769., with the various 
other determinations of the sun’s distance, and expressed his 
doubts whether any important improvement can be made in 1874 
and 1882,.—Mr. Birt then read a paper on the spots which are 
visible on the floor of the lunar crater Plato, of which he exhi- 
bited an interesting drawing.—Mr. Browning read a paper on 
the changes of colour which the equatorial belt of Jupiter has 
recently exhibited ; and indicated the importance of a careful 
series of observations directed to the determination of any 
periodicity which may exist in these changes. —In describing the 
American photographs of the eclipse of last August, Mr. De la 
Rue remarked that they confirm the evidence already afforded by 
his own observations in 1860, and those of Major Tennant in 
1868, that the corona, in part at least, is a solar phenomenon.— 
The meeting closed with an announcement on the part of the 
Chairman, that a medal had been struck at the Imperial Mint,of 
France in honour of Hind, Goldschmidt, and Luther, on the 
occasion of the discovery of the hundredth planetoid in 1868. 
Geological Society, November 24.—Prof. T. H. Huxley, 
LL.D., F.R.S., President, in the chair.—Robert Armold Barker, 
M.D., Civil Medical Officer, Cachar, Bengal, was elected a 
Fellow of the Society.—The following communications were 
read :—(1), On the Dinosauria of the Trias, with observations on 
the Classification of the Dinosauria,” by Prof. Huxley, LL.D., 
F.R.S., President. The author commenced by referring to the 
bibliographical history of the Dinosauria, which were first recog- 
nised as a distinct group by Hermann von Meyer in 1830. He 
then indicated the general characters of the group, which he 
proposed to divide into three families, viz. :— 
I. The MEGALOSAURIDA, with the genera 7eratosaurus, Paleo- 
saurus, Megalosaurus, Potkilopleuron, Lelaps, and probably 
Luskelosaurus ; 
II. The SCELIDOSAURID#, with the genera Thecodontosaurus, 
Lhyleosaurus, Pholacanthus, and Acanthopholis ; and 
Ill. The IGUANODONTID&, with the genera Cefiosaurus, 
Iguanodon, Hypsilophodon, Hadrosaurus, and probably Ste- 
nopelys. 
Compsognathus was said to have many points of affinity with the 
Dinosauria, especially in the ornithic character of its hind limbs, 
but at the same time to differ from them in several important 
particulars. Hence the author proposed to regard Compsognathus 
as the representative of a group (Compsognatha) equivalent to the 
true Dinosauria, and forming, with them, an order to which he 
gave the name of ORNITHOSCELIDA. ‘The author then treated 
of the relations of the Ornithoscelida to other Reptiles. He in- 
dicated certain peculiarities in the structure of the vertebrae which 
serve to characterise four great groups of Reptiles, and showed 
that his Ornithoscelida belong to a group in which, as in existing 
Crocodiles, the thoracic vertebrae have distinct capitular and 
tubercular processes springing from the arch of the vertebra. 
This group was said to include also the Crocodilia, the Anomo- 
dontia, and the Pterosauria, to the second of which the author 
was inclined to approximate the Ornithoscelida. Asa near ally of 
these reptiles, the author cited the Permian Parasaurus, the 
structure of which he discussed, and stated that it seemed to be a 
terrestrial reptile, leading back to some older and less specialised 
reptilian form. With regard to the relation of the Omithoscelida 
to birds, the author stated that he knew of no character by which 
the structure of birds as a class differs from that of reptiles which 
is not foreshadowed in the Ornithoscelida, and he briefly discussed 
the question of the relationship of Pterodactyles to birds. He 
did not consider that the majority of the Dinosauria stood so 
habitually upon their hind feet as to account for the resemblance of 
their hind limbs to those of birds, by simple similarity of function. 
‘The author then proceeded to notice the Dinosauria of the Trias, 
commencing with an historical account of our knowledge of the 
oceurrence of such reptilian forms in beds of that age. He 
identified the following Triassic reptilian-forms as belonging to 
the Dinosauria:— 7erat:saurus, Platwosaur us, and Zanclodon from 
the German trias ; Zhecodontosaurus and Paleosaurus from the 
Bristol conglomerate (the second of these genera he restricted to 
P. cylindyodon of Riley and Stutchbury, their P. A/atyodon being 
referred to Thecodontosaurus); Cladyodon from Warwickshire ; 
Deuterosaurus from the Ural; Avhistredon from Central In- 
dia; Clepsysaurus and Bathygnathus from North America ; 
and probably the South African Pristerosaurus.—Sir Roderick 
Murchison, who had taken the chair, inquired as to the lowest 
formation in which the bird-like character of Dinosaurians 
was apparent, and was informed that it was to be recog- 
nised as low as the Trias, if not lower.—Mr. Seeley insisted on 
the necessity for defining the common plan both of the Rep- 
tilia and of the ordinal groups before they could be treated of in 
classification. He had come to somewhat different conclusions 
as to the grouping and classification of Saurians from those adop- 
ted by the President. This would be evident, in so far as 
concerned Pterodactyles, from a work on Ornithosauria which he 
had just completed, and which would be published in a few days. 
—Mr. Etheridge stated that the dolomitic conglomerate, in which 
the Thecodont remains occurred near Bristol, was distinctly at the 
base of the Keuper of the Bristol area, being beneath the sand- 
stones and marls which underlie the Rheetic series. There were 
no Permian beds in the area. He regarded the conglomerates as 
probably equivalent to the Muschelkalk. It was only at one 
point near Clifton that the Thecodont remains had been found.— 
Prof. Huxley was pleased to find that there was such a diversity 
of opinion between Mr. Seeley and himself, as it was by discus- 
sion of opposite views that the truth was to be attained. He 
