620 
s newer than these volcanic series, thus solving a question of 
considerable interest. From this it follows that the boulders of 
granite found in the basement conglomerate of the volcanic 
series are not derived from the granite of the district, but must 
have come from some other area. 
Two papers were sent in by Dr. W. Mackie. The first dealt 
with the conditions under which manganese dioxide has been 
precipitated in the Elgin sandstone. The second gave the 
results of a series of determinations of the soluble chlorides and 
sulphates in the same sandstone, made with a view to test the 
theory that from such an examination it is possible to determine 
the character of the waters of the basin of deposit of sedi- 
mentary rocks. The result was of a negative character, and the 
author believes it is not safe to infer that the soluble salts of a 
deposit represent the salts of the original waters of the basin of 
deposition, 
English geology occupied a very small part of the time of the 
Section. Mr. Horace B. Woodward sent an interesting note 
relating to the Eocenes. A section on a new railway between 
Axminster and Lyme Regis shows a good. example of Bagshot 
strata near Combe Pyne Hill which serves to connect the beds 
of that age at Bournemouth with the deposit at Bovey Tracey in 
Devon. This last is now admitted to be of Bagshot age. It used to 
be called Miocene, but Mr. Starkie Gardner has long contended 
that it is equivalent to the Bournemouth Series. 
A paper on the fossil flora of the Cumberland Coalfield was 
read by Mr. E. A. Newell Arber, who described plants from 
both the Whitehaven sandstone and the Coal-measures. 
Mr. P. F. Kendall dealt with the Vale of Eden. He believed 
that he could show from the relative position of the Permian 
breccias or Brockrams that a movement of the Pennine faults 
had taken place in Permian times. 
There was one paper relating to Wales. It was by Mr. 
W. G. Fernsides, who described some new faunas which he had 
obtained at Pen Morfa, near Tremadoc. He described a zone 
with species of high Lingula Flag type 30 feet below the Lower 
Tremadoc. Some 30 feet above the horizon of Ramsay’s Lower 
Tremadoc fossils, he had found a continuous zone of Dictyonema, 
and had mapped its outcrop for more than five miles. Finally, 
some 400 feet above the Dictyonema, he had found a 
Shineton fauna with a number of Swedish forms and some new 
species. 
Passing now to papers dealing with localities outside the 
British Isles, we may mention a paper by Dr. R. H. Traquair 
on fishes of the Lower Devonian roofing slate of Gemiinden in 
Germany. They belong to the class with mailed bodies and are 
there associated with a fauna thoroughly marine in character, a 
point of considerable interest. The author showed some 
beautiful photographs of the fishes and of starfishes, crinoids, 
trilobites, corals, &c., from the slates. 
Indian geology was dealt with in an interesting note by Prof. 
II. G. Seeley. He said that hitherto there has been no evidence 
of Cretaceous strata in the Salt Range of the north of India, but 
he was now able to bring forward an account of a series of 
species found by Mr. E. G. Fraser on the shoulder of Sekasar. 
They are of the type or age of the Upper Greensand. 
Two papers dealt with Victoria, Australia. Mr. James 
Surling gave some notes on a new geological map of the 
colony, and Dr. Smith Woodward sent an account of some 
observations on a new Lower Carboniferous fish-fauna from the 
Broken River. Attention was first drawn to these Broken 
River fossils some twelve years ago, and the late Sir Frederick 
M’Coy described them as a mixture of Devonian and Carbon- 
iferous forms. This Dr. Woodward now shows to have been a 
mistake ; he considers them typically and essentially Carbon- 
iferous. Dr. Traquair said that he had seen the collection and 
could corroborate all the statements in the paper. Palzeon- 
tologists might now congratulate themselves that the myth 
which alleged the existence of fishes of Lower and Upper 
Devonian and Lower Carboniferous types in the same bed had 
been exploded. 
With regard to America, the only contribution was a paper 
by Dr. H. Woodward on the Middle Cambrian Trilobites of 
Mount Stephen, British Columbia. 
Most of the Palzeontological papers have already been noticed, 
but an interesting note on the tusks and skull of AZastodon 
angustidens, by Dr. C. W. Andrews, deserves mention, 
Prof. J. Joly brought forward a suggestive paper on the 
viscous fusion of rock-forming minerals, which gave rise to an 
NO. 1720, VOL. 66] 
NATURE 
[OcrozeER 16, 1902 
interesting discussion in which Mr. Teall, Prof. Grenville Cole 
and Dr, Johnston-Lavis took part. or ; 
Prof. J. I’. Blake read a paper on the original form of sedi- 
mentary deposits. He observed that during the continuance 
of constant physical conditions, the seaward boundary of river- 
brought deposits will be a marked line. Such a line has been 
called an escarpment and the edge of the continental plateau, 
but the author believed it to be the limit of terrigenous deposits 
in bulk. He also considered that limestones are most likely to 
form deposits of lenticular shape with the long axis parallel to 
the shore, and when they are found to give place to shales we 
should infer that we are approaching a river or other source of 
sediment. 
In conclusion, we may mention that a series of excursions to 
places of geological interest was arranged by Messrs. G. W. 
Lamplugh, J. St. J. Phillips and H. J. Seymour, and were much 
appreciated by the geologists present at the meeting. 
CARBON AND PLANTS. 
JN a paper recently laid before the Royal Society, dealing with 
the physical processes which regulate the entry of atmo- 
spheric carbon dioxide into the leaves of plants,* the authors 
incidentally described a series of experiments relating to the 
rate of absorption of dilute gaseous carbon dioxide by surfaces 
of solutions of caustic alkali, when air containing definite small 
amounts of this gas is drawn over the liquid. Contrary to what 
might be expected from the perfect absorbing nature of the 
solution, and the known laws of gaseous diffusion, the amount 
of CO, absorbed by unit area of the liquid surface in unit time 
ceases sensibly to increase when a comparatively low velocity of 
the moving air current has been reached. This, however, only 
holds good when the proportion of CO, in the air stream is 
maintained quite constant, any slight variation in the amount at 
once affecting the rate of absorption. On investigation, it was 
found that for dilutions of carbon dioxide lying between 0°6 
part and 6 parts per 10,000 of air, the rate of absorption of the 
carbon dioxide zs stréctly proportional to its partial pressure. 
In determining the rates of gaseous diffusion of atmospheric 
carbon dioxide through multiperforate diaphragms extended 
over chambers containing perfect absorbents, the same relations 
between partial pressure of the gas and its absorption were 
found to hold good; under these conditions the amount of 
carbon dioxide passing through the diaphragm in a given time is 
also directly proportional to the density of that gas in the 
moving stream of air which flows over the outer surface of the - 
diaphragm. 
But this latter case exactly defines the physical conditions 
under which atmospheric carbon dioxide enters the tissue of a 
living leaf, the muluperforate diaphragm being represented by the 
cuticle and epidermis, pierced with numerous stomata, and the 
inner absorbing chamber by the intercellular spaces of the paren- 
chyma, bounded by the chlorophyll-containing cells in which 
the process of photosynthesis goes on (/oc. cét.). 
The authors have now found, by enclosing the living leaves in 
-glass cases through which air containing known proportions of 
CO, is passed, that a living leaf is really able, within certain 
limits, to respond to increased amounts of carbon dioxide in the 
air surrounding it, in such a manner as to indicate an approximate 
proportionality between tke photosynthetic work it can accom- 
plish and the partial pressure the gas exercises in the air 
bathing the leaf surface. 
The following experiment may be selected from several, in 
illustration :— 
Experiment /.—In this case, comparative experiments were 
made on two successive days in August, 1898, with two similar 
leaves, A and B of Helianthus annuus whilst still attached to 
the plant. These were exposed to the strong diffused light of a 
clear northern sky under as nearly as possible identical condi- 
tions, with the exception of the composition of the air drawn - 
through the cases, 
Over leaf A was drawn normal air containing 2°8 parts per 
10,000 of CO,, whilst the air passing over leif B contained 
25°53 parts CO, per 10,000. 
1 Abridged from a paper on “The Influence of Varying Amounts of 
Carbon Dioxide in the Air on the Photosynthetic Process of Leaves and on 
the Mode of Growth of Plants,” by Dr. Horace T. Brown, F.R.S., and 
Mr. F. Escombe. Read before the Royal Society on May 29. 
2 Phil. Trans., B. 1900, vol. exciii. p. 278. 
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