560 Reviews. [July, 
volume, while this last edition has not only expanded into a goodly 
octavo volume, but the contents have increased in value, as the subject 
has advanced in importance. Those who are interested in the matter 
merely as one of science, cannot do better than consult Mr. Hogg’s 
book, as they will find in it all that they need ; while those professional 
men who desire to use the instrument and become qualified to esti- 
mate its value, will do well carefully to study its contents; for, as 
it is one of the latest, so it is one of the most complete, publications 
in the English language on the subject. Its illustrations, woodcuts, 
and coloured lithographs of the interior of the eye in health and dis- 
ease cannot fail to be of considerable use to the beginner. These 
coloured views are not only more numerous, but also better executed 
than those in the first edition of the work; still we would call the 
author's attention to the magnificent illustrations recently published 
by Liebreich in the ‘ Atlas d’Ophthalmoscopie,’ which as works of art 
have never been exceeded in beauty of execution, as well worthy of 
rivalry, when another edition of his book is called for. We well 
know the difficulty and cost attendant upon the illustrations of such a 
character, but we cannot doubt that artists in England may be found 
who are equal to the task, and the extra outlay would be well repaid 
by the greatly-increased value of pictures which shall equal in deli- 
cacy and beauty the original structures which they represent. 
The pamphlet by Dr. Rosebrugh is a reprint, from a Canadian 
Journal, of a paper read by him in January last before the Canadian 
Institute, in which he describes a new ophthalmoscope he has lately 
invented for obtaining a photograph “ of the posterior internal surface 
of the living eye.” It would be very difficult to convey a clear idea 
of the apparatus without diagrams. It, however, essentially consists 
of a modified ordinary photographing camera, in which the tubes and 
lenses are so arranged, that near their juncture is placed a polished 
plate of glass, with parallel surfaces, inclined at such an angle to the 
tubes that a part of the light enterimg by the illuminating tube is re- 
flected, at right angles to its original direction, into the dilated pupil 
of an eye, from which it isagain reflected upon the back of the camera, 
when, instead of the image being received upon an ordinary ground- 
glass screen of a camera, it falls upon a properly sensitized collodion. 
glass, upon which, by about five seconds’ exposure, a negative picture is 
impressed. This negative is then used in the ordinary way for print- 
ing the positive photographs, 
Though Dr. Rosebrugh does not yet appear to have succeeded in 
photographing the human eye, he states that he has obtained an im- 
pression of the eye of a cat, while the animal was under the influence 
of chloroform, which condition, however, he hardly thinks necessary, 
seeing that its impression can be obtained in so short a space of 
time. 
We welcome with much pleasure this ingenious attempt to still 
further extend the important applications of light painting, which of 
late have received so many new extensions; we can hardly conceive of 
any that can be more valuable than this suggestion, for not only are 
the structures so minute and so delicate, but so varied and so nu- 
