PROCEEDINGS OF SOCIETIES. 193 
as micrometers for the microscope, intending eventually to 
bring the subject before this Society. I employ for the pur- 
pose an apparatus of my own, which has been described in 
the ‘ Photographic Journal,’ as adapted to the production of 
micro-photographs generally. I think that the method of 
printing these scales, recommended in the paper just read, 
will not give sufficiently fine results for the purpose proposed, 
namely, the construction of a photographed scale whereby 
the distance of some part of a slide may be measured from a 
fixed point. I very much prefer wet collodion for these 
minute lines, and reduce the scale from a large one by two 
operations—one in the camera, to obtain a negative, and 
another in the apparatus just mentioned, using a microscopic 
object-glass as the reducing lens. The beautifully perfect 
minute pictures which have already been produced on wet col- 
-lodion prove that we can thus get all we want in sharpness and 
distinctness. With regard to this plan for the production of di- 
vided scales by photography, I am disposed to think that it has 
many advantages. One very important one is that any error 
in the large scale will be reduced in direct proportion to the 
reduction of the whole. Thus, an original error of, say, the 
50th of an inch, reduced 100 times, becomes the 50,000th of 
aninch. For use on the stage, however, these photographed 
scales, whether as finders or micrometers, would not be good 
under high powers, inasmuch as the silver deposit would be 
so much magnified as to separate its particles. Measuring by 
the stage micrometer is scarcely possible except with a low 
power, but is perfectly easy when the divided scale is placed 
in the eyepiece, in which position this objection to a photo- 
graph would scarcely apply. 
Mr. Jackson remarked that if the squares were only the 
100th of an inch on the side, it might be difficult to print 
the figures with sufficient distinctness from a negative of the 
same size by contact ; and suggested that a negative of three 
or four inches square should first be taken, and the finders 
should be reduced to the exact size and printed on wet collo- 
dion by means of a small fixed camera, much in the same 
manner as he had adopted for printing the microscopic por- 
traits. He also recommended that the figures should be 
written in what has been termed Egyptian type, that is, with 
the up strokes and down of the same thickness ; and he ex- 
hibited the photograph of a card, taken in the above manner, 
in which such letters were quite plain when reduced to 
1000th of an inch in height. 
“On the Miliolitide of the East Indian Seas,” by W. K. 
Parker, Esq. (‘Trans.,’ p. 53.) 
