SCIENTIFIC SUMMARY. 
133 
inches high, and is provided with a base six inches square, to insure steadi- 
ness. At the aperture in the centre of the anterior side, a brass collar 
is fitted, through which the tube containing the lenses slides. At the 
opposite side of the camera is a central aperture, 2^ inches square, behind 
which is the ground, or focussing glass, also 2^ inches square, moving 
in grooves, &c., in the ordinary way. The mode of using the instrument 
is thus described : — A table being placed in the sunlight, the shutters 
are closed, and a beam of light admitted the size of the illuminating tube ; 
but this is not absolutely essential if the diffused light is excluded from the 
camera, and the usual focussing cloth used. The camera and tube being in 
their proper positions, a cone of light will issue from the end of the camera- 
tube through the centre of the aperture in the diaphragm, forming a focus 
about half an inch from the outside of it. The cat or rabbit to be experi- 
mented upon (the inventor has not yet applied it to the human eye) is secured 
in a box of the rec|uii?ed size, with the head projecting through an aperture 
prepared so as to retain it in one position. An image — ^very clear and bright 
— of the optic nerve, vessels, &c., can then be obtained by focussing while 
the eyelids of the patient are held apart by an assistant, the pupil of the eye 
to be operated upon having been previously dilated with atropine. The in- 
verted image on the ground-glass, when in focus, gives the optic-nerve 
entrance, distribution of the arteries, the veins, &c., very distinctly and mag- 
nified about four diameters. This is then photographed in the ordinary way, 
the exposure being about five seconds, although this might be considerably 
abbreviated, we should think. In ophthalmic examinations of the interior of 
the eye, artificial fight should be employed ; the best being that from the 
gas argand-burner arranged as a table-lamp, with flexible tube attached. The 
flame should be brought within two or three inches of the entrance of the 
illuminating tube, and the instniment placed on the same horizontal fine. 
A screen to shade the ground-glass and the observer’s eye should be used. 
At the conclusion of his valuable communication, Mr. Kosenburgh said he 
hoped his “ instrument might contribute something towards awakening an 
increased interest in ophthalmoscopic science, as the ophthalmoscope is, with- 
out doubt, as essential in investigating diseases of the eye as the stethescope 
in diagnosing affections of the heart and lungs,” and trusted “ its use would 
aid in banishing from ophthalmic nomenclature the indefinite term ‘ amamnsis,’ 
where, as Walther states, ‘ the patient and the physician are equally blind.’ ” 
Photographing Electric TAglit — The Astronomer Eoyal of Scotland (Pro- 
fessor Piazzi Smyth) in a letter to the British Journal of Photography, of 
August 5th, calls attention to a singular electrical effect produced in a dry 
plate negative of some house-roofs. Every chinmey-top was surmounted in 
the print by white streaks of fight (black in the negative), although nothing 
of the kind was detected either in the scene itself or on the focussing glass. 
The lens employed was a good one, the stop a small one (0‘3 inch), and the 
definition obtained, of course, extremely sharp and clear. The Professor con- 
cludes, after a careful consideration of all sorts of possible and impossible 
causes, that the phenomenon was “ an electrical one, invisible to the eye, but 
abundantly visible or sensible to the photographic camera, and the occasion 
was perfectly agreeable thereto ; for it was at the conclusion of a week of 
unusually hot, calm weather, and the sky had that morning become clouded 
