REPORT OF MEETINGS. 
33 
a screen of coloured starch grains before reaching the sensitive 
film. A negative image is first developed ; this is subsequently 
changed to a positive by dissolving the silver salts acted on by the 
light, and then allowing daylight to act on the silver salt that is left. 
The picture is then seen as a transparency, the light passing through 
the colour screen before reaching the eye. The lecturer showed a 
spectrum of the light transmitted by the individual starch grains, 
and indicated that, in his opinion, there was too little overlapping 
in the different kinds of light ; and this was borne out by an auto- 
chrome photograph of the solar spectrum, which showed merely 
three uniform bands of colour separated by darker intervals. The 
colour effects of over — and under — exposure were described, and 
the lecturer suggested how this defect could be remedied by 
increasing the density of the starch screen, and consequently 
increasing the number of blue starch grains. Slides illustrating 
different types of failures were next shown, and remedies were 
suggested, amongst others the binding of the slides with com- 
pensating colour screens to correct defects of colour due to wrong 
exposures. After these some fine autochromes of various subjects 
were shown, some views in the Tyrol and autumn tints on Clifton 
Down being exceptionally good. 
April 1 2th. — Fourth General Meeting. The Chairman raised the 
question, “ Is the snowdrop indigenous to Britain ? ” No mention 
of this flower is made until the middle of the 17th century, but 
as it is only in the West Country that it has the appearance of 
being wild, it is quite possible that few people in those days knew 
of its existence. In North Somerset it grows in such abundance 
and so far from gardens that one is much inclined to conclude that 
there it must be indigenous. Professor Lloyd Morgan brought 
before the members a scheme for the preparation of a raised model 
of the Avon Gorge and the surrounding district. After saying a 
few words on the uses of such a model, and showing maps and 
photographs on the screen. Professor Lloyd Morgan described two 
methods that might be employed to build the model. The first was 
to paste 6-inch ordnance survey maps on cardboard, cut them 
out along the contour lines, and then superpose the cardboards, 
separating each higher level of 100 feet from the one below by an 
inch of plasticine. Another method was to take sections across the 
ordnance map at intervals of an inch, cut out these sections in 
cardboard, stand them in rows an inch apart, and fill up the spaces 
between with plasticine. Dr. Munro Smith showed a series of 
lantern slides made from magnificent photomicrographs to illustrate 
the structure of the cell and different types of cell. 
May 6th. — Fifth General Meeting. Mr. A. M. Tyndall, B.Sc., 
read a paper on “Electric Discharges in the Atmosphere.” The 
lecturer remarked that whatever view was at present taken of the 
nature of electricity, it was still very convenient to regard it as of 
two kinds, positive and negative, always tending to neutralise one 
another. When the tendency becomes great enough to overcome 
