2 
TRANSACTIONS OF THE SECTIONS. 23 
and exerts its influence beyond them—and that the luminous phenomena are exhi- 
bited under two modifications, the vibratory or permanent, and the undulatory or 
transient state. This theory leads to the conclusion that the undulations within the 
substance of material bodies communicate their vibrations to the ethereal medium 
without them, and thence to the same medium within the eye. If the undulations 
be such as to produce red, red is seen by the eye, and so for other colours. Now, 
as we have films eminently sensitive to the action of reflected light, and capable 
occasionally of being coloured by such light, it is clearly within the laws of physical 
science to suppose that the several portions of the excited film may retain within 
themselves, in the vibratory and permanent state, the varying undulations of the 
coloured objects whose images they receive. A picture with the colours as in 
nature would be the result, instead of the mere black and white mezzotint at 
present obtained. The desiderata are—a sensitive silver compound capable ot 
yeceiving and transmitting the undulations, and energetic reflexions from the 
objects themselves. 
hortly before the meeting he happened to obtain unusual traces of colour in 
photographie portraits. The chief difference in manipulation was a slight excess of 
the iodizer in the collodion, and the addition of acetic acid and acetate of soda to 
the bath, And in order more fully to test the effect of the cadmium and bromo- 
iodizers, he increased the quantity until natural colours ceased to be strengthened. 
The final proportion of iodizing solutions gave the portrait which was exhibited. 
The general warm colours of the forehead and face, and the tone of the coat were 
fairly represented in the portrait. 
Remarks on the Complementary Spectrum, By J, Surtu. 
The author endeavoured to explain, on the principle adopted by him in his chro- 
matrope experiments, the well-known fact that the spectrum of a hole in the win- 
dow-shutter, when received on a screen, has the violet end above and the red below, 
but when looked at through the prism, the red appears above and the violet below. 
On the Motion of Camphor, &c. towards the Light. 
By Cuantxs Tomtinson, King’s College, London. 
Books on chemistry from the time of Chaptal (1788) to the present, recognize 
the fact that salts in crystallizing move towards the light; that camphor, water, 
alcohol, &c. form deposits on the most illuminated side of the bottles that contain 
them. The history of the subject includes the names of Petit, Chaptal, Dorthes, 
Draper, &c. Chaptal’s experiments were made with saline solutions, and he found 
that crystalline deposits could be determined to any point by admitting the light to 
that point, or prevented by shutting out the light. Dr. Draper, who named these 
phenomena perihelion motions, found that in the case of camphor deposits were 
sometimes made nearest the sun, and at other times furthest from him, the latter 
being termed aphelion motions; that reflected light and coloured light produced 
aphelion movements ; that the deposits are not produced in the dark, or by artificial 
light, and that rings and disks of tinfoil prevent the formation of deposits. He 
supposed electricity to be concerned in the production of these phenomena. 
Mir Tomlinson shows that neither light nor electricity has anything to do with 
these effects, but that they are the simple results of cooling. By treating the 
vapour of camphor, &c. as dew, all the effects follow; and Chaptal’s results are 
obtained in full sunshine without any shutting out of the light, but simply by 
preventing radiation by means of transparent screens. When a bottle containing 
camphor, &e. is exposed to light, the illuminated side is generally the colder, and 
hence the deposit on this side; but when the sun is shining on the bottle, the 
furthest side is the colder, and there the deposit takes place. Bottles of camphor 
kept in the dark, 7. e. in a cupboard or drawer, are equally warm all round, and 
hence no deposit is formed; but if such a bottle be cooled on one side by means of 
a piece of filtering-paper dipped in ether, a deposit is instantly formed. If a bottle 
of camphor be plunged into water at 100° no deposit is formed, because it is equally 
hot all round. If a number of bottles be covered with opake substances and 
exposed to the sun, or to a heated cannon-ball, deposits are formed or not according 
