SCIENTIFIC SUMMARY. 
393 
arts, promises to bear good fruit in the shape of an unusually admirable 
show of attractive and artistic specimens. The managers have done well 
also in grouping the separate collections contributed from different countries 
together, preserving their distinctiveness, and yet securing that amount of 
unity which is essential to comparing the relative degrees of progress made 
by foreign and British professors. By this means also a broader and simpler 
effect is obtained generally, and the student or observer is very much less 
wearied and confused in passing through so large, so greatly varied, and so 
important a collection. Those who visited the last international exhibition 
will understand the superiority of the Dublin arrangement to that of the 
Commissioners of 1862. The same spirit of order will be recogmized in the 
classification of the various branches and departments of photography. It 
is evident that earnestness and singleness of purpose are at the root of efforts 
so judiciously and meritoriously conducted. 
Neiv Method of Printing. — A method of printing photographs on ivory 
and wood, first suggested in “ The Art Student,” and since then taken up 
experimentally and conducted to a satisfactory result, appeared recently in 
the pages of the Photogra])hic Neivs. Mr. G. W. Simpson, the editor of the 
above serial, thus describes the process : — ■ 
“We have used a collodion made from a somewhat powdery pyroxyline, 
satimated with nitrate of silver, and containing about four grains of nitrate 
of silver to each ounce. A tablet of ivory prepared for miniature-painting 
is coated with this collodion, and exposed under a negative. It prints some- 
what more slowly than paper, tends to produce a more vigorous image, and 
requires very little over-printing, especially if submitted to a bath of dilute 
acetic acid before toning and fixing ; for we find that with Wotldytype prints 
the image is much less reduced during toning and fixing if it have been 
submitted to the bath of acetic acid and water first. By remaining in this 
solution five or ten minutes, the uranium salt is dissolved out of the film, 
and the print may now be submitted to the action of a toning and fixing 
bath, consisting of gold and sulpho-cyanide of ammonium, such as we have 
before described ; or it may be toned in a bath of chloride of gold and 
acetate of soda, and then fixed in a solution of sulpho-cyanide of ammonium, 
one part in ten of water. We have tried both plans, and with ivory have 
obtained the best results by using tha acetate bath. A thorough rinsing 
completes the operation. 
“When the picture is completed and dried, it possesses, of course, a sim- 
face of collodion. This, to some colourists, would not be regarded as an 
objection, the collodion surface being a very pleasant one on which to colour ; 
but for those who desire the peculiar surface of the ivory itself, the collodion 
may be easily removed. A few drops of ether are poured on the surface, 
and the film removed with a tuft of cotton wool ; the surface is finally rinsed 
with ether to remove the final traces of the collodion, and the picture is 
finished. It will be found that, notwithstanding the removal of the coUodion, 
the image is not impaired, but remains vigorously impressed on the surface 
of the ivory itself. If the film of collodion were thick and of a horny cha- 
racter, the tone of the picture on the ivory will be a little redder than before 
the removal of the film ; but with a porous, permeable collodion, the toning 
action appears to pass completely through to the ivory itself. 
