642 



NA TURE 



[October 24, 1907 



forences. His influence on the research done by his 

 jnipils at Manchester is easily traced, and all of them 

 would acknovvledg^e the inspiration and encourage- 

 ment of many a half-hour's chat with the professor, 

 perambulating- the corridor to and fro in a thoroughly 

 characteristic manner. 



Some months ago Prof. Schuster announced his in- 

 tention of vacating the chair of physics to allow more 

 leisure for the literary work and theoretical research 

 to which he has recently devoted himself more par- 

 licularly. To the satisfaction of his colleagues at 

 Manchester, it has been decided, however, that his 

 connection with the college shall not cease, but that 

 he will continue to direct some of the research, and 

 Ihe council has therefore appointed him " honorary 

 professor." His place as Langworthy professor and 

 director of the laboratory has been' filled bv the 

 appointment of Prof. E. Rutherford, F.R.S., of'Mont- 

 real, who arrived in Manchester a short time ago and 

 organised some researches, though not nominally in 

 charge of the laboratories until the commencement of 

 the October session. Prof. Schuster at present is 

 engaged in the study of the permeability of iron at 

 high temperatures under high pressures, especially 

 with a view to discover the effect of high pressures in 

 clianging the temperature, between 800° and 900° C, 

 when the metal suddenly loses most of its magnetism. 

 Pressures up to 1000 atmospheres are contemplated. 

 .A second problem under investigation is the effect on 

 the rate of decomposition of radio-active substances 

 of extremely high pressures, such as are met with 

 deep down in the earth's crust. In both these 

 problems the design of the high-pressure portion of 

 the apparatus has been due to Dr. Petavel, and for 

 tlie latter purpose Mr. Cook, the university 

 inechanician, has succeeded in constructing a com- 

 bined pump and ram, in which pressures up to 37,000 

 pounds per square inch can be maintained without 

 perceptible leak over long periods. The effect on 

 radium of pressures up to 2000 atmospheres has been 

 studied, and an account of the experiments will be 

 ready shortly. 



The accompanying photograph of Prof. Schuster in 

 the laboratory was taken specially by Mr. Warwick 

 Brookes. J. A. Harker. 



A ^EW METHOD OF COLOUR PHOTO- 

 GRAPHY. 

 T^HE latest method of colour photographv is dis- 

 ■■• tinguished as the " Warner-Powrie "' process, 

 and is well illustrated at the first exhibition of the 

 Society of Colour Photographers, which will close on 

 October 26. It will presumably be some little time 

 before the plates are generally obtainable, but so far 

 as can be judged from the e.xamples shown and the 

 details of their preparation, it is a process that will 

 offer special advantages. Mr. Powrie has been work- 

 ing at the subject for many years, and has succeeded 

 in producing a triple-coloured lined screen with better 

 and finer lines than has been possible by previous 

 methods, and without either gap or overlap. He dis- 

 cards ruling in favour of a very ingenious method 

 of printing that does away with all need for the 

 troublespme registration that becomes almost impos- 

 sible with fine lines. The glass is coated with a 

 bichromatcd colloid, exposed under a black-lined 

 screen that has spaces half the width of the lines, 

 and developed in warm water. This leaves the 

 colloid in lines with spaces of bare glass twice as 

 wide as the lines. By immersion in a solution of a 

 green dye the lines are stained, and bv the application 

 of formalin or chrome alum the collo'id is made quite 

 NO. I9S2, VOL. 76] 



insoluble and the dye fixed. The plate is coated 

 again, exposed under the same black-lined screen, 

 the only precaution being that the green lines already 

 made shall be covered with the black lines of the 

 overlying screen. After exposure and development 

 the plate is immersed in a solution of a red dye 

 to stain the second set of lines, and again treated 

 with a hardening agent. The plate is coated once 

 more, and this time exposed alone with its back to 

 the light, so that the red and green lines already made 

 serve to protect the coating from light action. So 

 after development all the remaining spaces are exactly 

 filled with colloid, and this is then dyed blue. The 

 prepared plate is coated with a suitable photographic 

 emulsion, and can be used in a similar way to the 

 " autochrome " plates of Messrs. Lumiere, which we 

 have already described. The chief difference between 

 the two apparent by mere inspection is that the 

 colours are in lines instead of as a random grain. 

 But the lines can be made so fine that they are in- 

 visible to a normal eye without assistance. 



It is obvious that the " autochrome " and the 

 " Warner-Powrie " plates, and any plates in which 

 the surface is apportioned to three colours for colour 

 reproduction, must absorb about two-thirds of the 

 light that would pass through them if the colours 

 were not there. A simple colour, such as red, is 

 produced by a silver deposit that covers the green and 

 blue colours that are in the area that is required to 

 be red, and this area is therefore one-third red and 

 two-thirds black. A print on a " bleaching-out " 

 paper (as the " Uto ") would give its colours mixed 

 with a double area of black, and therefore be use- 

 lessly dark. It is difficult, if possible, to obviate this 

 with a random distribution of the colours, but Mr. 

 Powrie, with his plates, overcomes the difficulty by 

 separating the plate and the paper with a thin sheet 

 of celluloid or glass, and by two mirrors on opposite 

 sides of the printing frame gets oblique light in two 

 directions, as well as direct light at right angles to 

 the surface, and so causes each coloured line in the 

 plate to give a line on the printing paper three 

 times its width. In this way, each colour — red, green 

 and .blue — produces its effect over the whole surface 

 of the paper, the colour patches are continuous (free 

 from black), and what should be white parts are com- 

 pletelv bleached instead of being: coloured like the 

 original. In the same way, but using ordinary 

 plates, and red, green and blue light separately for 

 the exposures, a separate negative can be obtained of 

 each of the three colours, with a continuous image on 

 each, and these can be used for any method of three- 

 colour printing. A single exposure on a single plate 

 will thus give all that is necessary for the preparation 

 of the three colour records which hitherto have been 

 obtained by separate and generally consecutive expo- 

 sures on the original. C. J. 



MR. HOWARD S.AUNDERS. 



IT is with unfeigned regret that we record the 

 death of Mr. Howard .Saunders, after a long and 

 painful illness. Mr. Saunders was born in London 

 in 1835, and was therefore seventy-two at the time of 

 his death. He was educated privately — to a great 

 extent at Dr. Gavin Smith's school at Rottingdean, 

 near Brighton, where he is said to have developed 

 that taste for ornithology by ineans of which he 

 attained eminence in later years. Immediately after 

 leaving school he entered on a business career, and 

 at the age of twenty joined a mercantile house at 

 Callao. Five years were spent by him in Chili and 

 Peru, where archaeological studies appear to have 



I 



