SEPTEMBER 28, 1899] 
THE ROVAL PHOTOGRAPHIC SOCIETY’S 
EX AIBITION. 
HE forty-fourth annual exhibition of the Royal Photographic 
Society was opened to the public last Monday at the 
Gallery of the Royal Society of Painters in Water Colours, 5 
Pall Mall East. As is usual, by far the greater number of the 
exhibits claim‘attention on account of their pictorial interest ; 
but the technical and scientific section is considerably larger 
than it has been at the recent exhibitions. No doubt next year 
there will be a still further increase in the importance of this 
section, as the Society will then have at their disposal the larger 
accommodation available at the New Gallery in Regent Street. 
The judges in this Section, Captain Abney, Mr. T. Bolas 
and Mr. Chapman Jones, have selected three of the exhibits as 
showing progress of sufficient importance to merit the special 
distinction of receiving the Society’s medal Taking these as 
they stand in the catalogue, the first is awarded for copies of an 
etching, a mezzotint, a silver print, an engraving, a lithograph, 
a pen and ink drawing and a pencil drawing, by Mr. J. Hort 
Player, by what he calls the ‘‘absorption” process. The 
method is to place the picture or document that is to be copied 
face uppermost, to lay upon it a piece of ‘‘ bromide paper ” with 
its sensitive surface in close contact with the picture, and then 
to expose with the bromide paper towards the light, so that the 
light passes through the sensitive surface before it comes in con- 
tact with the picture being copied. On development this fur- 
nishes a negative from which prints are obtained as usual. 
The great advantage of the process is that the picture or docu- 
ment need not be transparent, or if it is on ordinary paper 
there may be other writing or drawing on the reverse side. 
Those who examine these specimens of Mr. Player's will 
be surprised at the wonderful perfection to which he has 
brought the process, and its universal applicability is proved 
by the great variety in the character of the originals that he has | 
worked from, 
Another medal is awarded for a cross-lined screen for use in the 
making of half-tone photo-typographic blocks, by Messrs. J. E. 
Johnson and Co. It has two hundred lines to the inch over its 
whole area of thirteen by sixteen inches, the especial feature of 
the screen being the great regularity of the ruling and the free- 
dom from blemishes in so large a plate. Two still larger ruled 
screens are also shown by the same firm, of 133 and 150 lines to 
the inch respectively. 
Mr. E. Sanger Shepherd receives a medal for his ‘‘ tri- 
chromatic light filters.” The three-colour printing methods 
that have been brought to such perfection depend upon the fact 
that the phenomena of colour vision can be explained on the 
assumption of three colour sensations. By photographing separ- 
ately the light that affects each of these, and superposing the 
prints from the negatives, each being printed in its corresponding 
colour, the same sensation of colour will be produced by the 
resulting composite print as by the original. In order to photo- 
graph separately the colours that correspond to each sensation 
it is necessary to stop the light that is not wanted by means of a 
suitably coloured screen, which is generally placed against the 
lens. But these colour screens have also to compensate for the 
differences between the sensitiveness of the plate used for the 
different colours and their visual intensity. Heretofore we 
believe the colour screens have been prepared by the method of 
trial and error, and though astonishingly good results have 
sometimes been produced, we may well expect greater certainty 
and more definite success by the use of screens that have been 
adjusted by definite methods of measurement as these of Mr. 
Sanger Shepherd’s have been. 
Cadett ‘‘rapid spectrum plate” and tested by the colour 
sensitometer recently devised by Captain Abney. The exact 
tints are obtained by the superposition in each case of films 
variously dyed. 
Among the cameras shown, the ‘‘ Gambier-Bolton” hand 
camera by Messrs. Watson and Sons is worthy of especial 
attention, as embodying the requirements found by Mr. Bolton 
in his large experience in photographing animals, The camera 
is for 5 x 4 inch plates, and is by no means a compact apparatus 
suitable for carrying about for obtaining snap-shots. It is 
designed for lenses of much greater focal length than usual that 
the image may be large, and as the lenses must be rapid, they 
must be large and consequently heavy. The camera has many 
conveniences adapting it to the special work it is constructed 
for. The same exhibitors show the ‘*Kromaz” colour ap- 
paratus. This is somewhat analogous to Ives’ well-known 
NO. 1561, VOL. 60] 
The screens are adjusted to the | 
WATURE 
539 
‘*Kromscop,” its only merit presumably being that it is cheaper. 
Instead of taking a complete stereoscopic negative for each of 
the three colours, only two pairs of negatives are taken—one 
through a green screen, and one of the other pair through a red 
and the other through a blue screen. The view shown iscrude, 
and hardly comparable with the exquisite results obtained with 
Ives’ ‘* Kromscop.” 
The Lippmann interference colour process is exemplified by 
three photographs by Mr. Edgar Senior—two views and a 
spectrum of the arc light. These would show to better advan- 
tage if the correct position of the eye were indicated in each 
case. The views are very good specimens of the results ob- 
tainable by this method, but the spectrum is especially worthy 
of commendation. In addition to these there will be found 
upon the tables many little conveniences, some of a distinctly 
novel kind, that will prove of service to those who photograph 
either for scientific purposes or for mere pleasure. A small 
printing frame, with six slides so that the sensitive surface may 
be exposed in six separate strips, is exhibited by Messrs. Marion 
and Co., and is applicable to a great variety of experimental 
purposes; and a frame, by Mr. T. Webster, that opens like a 
book, the negative being entirely removed from the print, so 
that the whole of the print may be examined at any time, 
thoes perhaps not very novel in principle, is likely to prove 
useful. 
But the most remarkable of all the exhibits is not mentioned 
in the catalogue, although examples will be found on the tables. 
These are some plates prepared by General Waterhouse, the 
honorary secretary of the Society, to illustrate the fact that a 
polished surface of metallic silver is sensitive to light, and that 
the resulting latent image may be developed by mercury vapour, 
after the manner of daguerreotype plates, or by the methods of 
so-called physical development, after the manner of wet collodion 
plates. The exposures necessary are long, generally two to 
three hours, to direct sunshine in August. To exclude any 
effect of the stencil plate used as the negative to print from, a 
sheet of mica was placed between it and the silver surface, and 
the silver surfaces experimented with have been electroplated 
copper plates prepared for daguerreotype work, silver foil and 
commercial silvered glass, the surface in each case being 
polished with plate powder. The surfaces of other metals have 
given similar results. Many years ago Moser made similar ex- 
periments, developing the images with the vapour of water and of 
mercury, but (speaking without reference) we think that he did 
not go so far as to develop the images by the deposition upon 
them of silver from a solution. General Waterhouse seems to 
have brought these experiments and practical photography a 
little nearer together, and we shall receive with great interest 
any further results of his investigations. (At 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Dr. A. WILLEY, formerly Balfour Student of the University ot 
Cambridge, has been appointed Lecturer on Biology in Guy's 
Hospital. 
THE inaugural address of the coming session of the City and 
Guilds Central Technical College will be given at the College, 
in Exhibition Road, on Tuesday afternoon next, at three 
o'clock, by Sir Andrew Noble. 
Science makes the following announcement :—The plans for 
building the University of California, submitted by M. Bernard, 
of Paris, have received the first prize in the competition arranged 
by Mrs. Phoebe Hearst. The cost of the buildings is estimated 
at over 15,000,000 dollars. 
IN addition to 300,000 dollars subscribed from various sources 
for an endowment of Brown University, made on condition 
that 2,000,000 dollars be collected, Mr. John D. Rockefeller 
has offered to give 250,000 dollars on condition that 1,000,000 
dollars be obtained before the commencement of next year. 
A PROSPECTUS just received shows that the work of the South 
African School of Mines, Kimberley, is now carried on in suit- 
able premises, which were completed in the beginning of this 
year at a cost of about 9o000/. Of this sum, 2000/. was given 
by the Government of Cape Colony, 2000/. by the De Beers 
Company, and 5000/. was borrowed. The school has been 
established to carry out part of a scheme for the training of 
