TRANSACTIONS OF SECTION A. 519 



seemed common to most colour-blind persons. He took fasting a small dose of 

 santonine — a <:rain and a half dissolved in a small quantity of alcohol, and diluted 

 with water. In less than live minutes the dose took ell'ect ; the white table-cloth ap- 

 peared of delicate bluish-green colour, and all objects were seen as through spectacles 

 of that tint. He went into the garden to use his spectroscope, and could see all the 

 solar rays in unbroken series with scarcely perceptible variation. There was no 

 actual grey band in the green, but this portion of the spectrum appeared normal 

 and splendidly brilliant. Ilis condition, therefore, was not so abnormal as many of 

 bis colour-blind friends. He, however, liad to use a word of caution : he only took 

 a quarter dose, but his condition was so serious that he feared the worst conse- 

 quences, and had to take an emetic of mustard and warm water to give him 

 relief. 



8. On a new method of Printing Pltotographic Negatives, employing Living 

 Leaves in place of Sensitive Paper. By Walter Gardiner, M.A. 



Before coming to the immediate subject of his paper, the author described how 

 prints may be obtained from Protococci, or the free swimming swarmspores of many 

 green Alyfe. It is possible to take advantage of their sensitiveness to light. Into 

 one end of a water-tight box a thin glass plate is securely fitted. The negative to 

 be printed is then placed next the glass, film side nearest. The box is filled with 

 water containing a fairly large quantity of swarmspores, the lid is shut down, and 

 the whole is exposed to diffused light. In the case of a strong and well-developed 

 negative, the swarmspores swim towards the most highly illuminated parts : and 

 there in the greatest numbers : come to rest, and settle down upon the glass, so that 

 after some four or six hours, on pouring out the water and removing the negative, 

 a print in green swarmspores can be obtained. The print is dried, fixed witli 

 albumin, stained, and yamished. 



The author then dwelt upon the well-known fact that the whole of the animal 

 life upon the globe depends directly or indirectly upon the wonderful synthetic 

 formation of proteid and protoplasm which takes place in the living tissue of plants 

 containing chlorophyll, and stated that whatever is the exact chemical nature 

 of this process, this at least is clear, that the first visible product of assimilatory 

 activity is starch. The presence of this starch can be made manifest by treating a 

 decolorised leaf with a solution of iodine. The formation of starch only takes 

 place under the infiuence of light. If a plant be placed in the dark over night and 

 then brought out into the light the next morning (the desired leaves being covered 

 by a sharp and well-developed negative) starch is formed where light is transmitted, 

 and in greatest quantity in the brightest areas. Thus a positive in starch is pro- 

 duced which can be developed by suitable treatment with iodine. (A leaf so 

 developed was handed round to the audience.) The author showed that by suitable 

 washing and treatment with some soluble silver salt, silver iodine may be produced 

 and a permanent print obtained. 



9. A Mode of Photography. By John Hancock. 



A mode of photography in which, by the employment of a camera constructed 

 on principles similar to the anatomical formation of the human eyes, it is possible 

 to combine the two inverted pictures of the right and left retinre into one vertical 

 picture, at a point in the camera coinciding with the point in the brain where the 

 optic nerves from the right and left eye intersect. 



10. A new form of Self-Registering Aclinomcter. By Dr. A. Richardson. 



See p. 540. 



11. The Action of Magnetism on Photographic Plates. 

 By Philip Braham, F.C.S. 



During some investigatit)n3 I was pursuing concerning magnetism, I surmised 

 tiat photographic plates could be acted on by that force, but not having sufficient 



