Dec., 1889. 
REPORTS OF SOCIETIES. 
289 
attached to one part where the change from marine to freshwater 
species was well seen. Collections of fossil and other shells were 
shown at the close. 
OXFORD NATURAL HISTORY SOCIETY.—Tuesday, October 
22nd, 1889. First meeting of the session. The President in the chair. 
Forty-two present. After the formal business, Professor Sydney 
H. Vines, D.Sc., F.R.S., gave a lecture on “ The Nutrition of Plants.” 
He spoke chiefly of green plants, and showed how the food of plants 
was much simpler than the food of animals. G-reen plants derived 
their food from two sources—from the soil, which furnished their 
mineral food, and from the air, which gave gaseous food (carbon 
di-oxide). Animals were solely dependent on plants for their food, 
either directly or indirectly. He then pointed out how important 
“ leaf-green ” or chlorophyll is. It is the sole agent for absorbing car¬ 
bonic acid, the gaseous food of plants. Thus, it both feeds the plant 
and purifies the air. No other substance in a plant, nor anywhere 
else, can do it just in that way, and if there were no chlorophyll, 
there could be no organic life. And the lecturer rather seemed to 
think that the whole world might be said to depend upon chlorophyll 
for existence.—Tuesday, November 5th. Rev. J. W. B. Bell in the 
chair. The treasurer produced the statement of accounts with regard 
to the recent annual meeting of the Midland Union of Natural History 
Societies at Oxford, and was able to show the satisfactory result of a 
balance of £3 13s. 4d. remaining in his hands after the payment of all 
expenses. After the election of several new members and the proposal 
of others for election at the next meeting, Sir John Conroy gave a 
lecture on the “ Causes of Colour.” The lecturer confined his remarks 
to physical causes, excluding physiological, dealing only with pigment 
colours. Pointing out that the wave motions of what we agree to call 
ether produce in us the sensation of colour, the lecturer proceeded to 
illustrate Newton’s doctrine of the composite colour of white light by 
throwing on a screen a beam from the oxyliydrogen lantern, and then 
refracting it through a carbon bisulphide prism on a white background 
to show the complete spectrum. Afterwards, letting the refracted ray 
fall upon backgrounds of red and green, he showed how certain rays 
only were reflected from each, and from a black ground none ; finally, 
passing along the spectrum a stick of red sealing wax, which, at first 
invisible at the violet end, and only becoming slowly distinguishable 
in its progress, finally glowed like molten metal on reaching the red 
end. Then, passing sheets of coloured glass before the ray, he showed 
that this reflection was due to the absorption of certain rays, and the 
free passage of others through the variously coloured glasses, from 
which the conclusion resulted that the colours of natural bodies must 
vary with the colour of the light incident upon them. This conclusion 
was further illustrated by exhibiting under different coloured light, 
yellow, red, and green, produced by the burning of sodium, lithium, 
and thallium, a red disc fixed on a grey background, which, under 
the varied light, appeared in each instance of a widely varied colour. 
The lecture closed with a striking experiment whereby a piece of 
gaudily-coloured wall paper in blues, reds, and greens, when illuminated 
by sodium light, showed its pattern in sober harmonies of greys and 
browns, an effect traced to the reflection of the sodium rays from the 
white background on which the pattern was stamped through the 
gaudy colours of its surface. No discussion followed, but a hearty 
vote of thanks was accorded to the lecturer. The Rev. J. W. B. Bell 
