REVIEWS. 
177 
publisher has done well in bringing- out a new series. The volume edited 
by Professor Carey Foster was devoted to magnetism and electricity, and 
was modified by him in accordance with the advance of scientific know- 
ledge. The present volume, on Optics, has been entrusted to Mr. T. 0. 
Harding ; but the result in this case has, though good, been by no means so 
successful as in the former instance. The chapter on the eye, the micro- 
scope, and on photographic optics, are to our mind not at all what they 
should be, and give us the idea that the editor has more mathematical 
knowledge than general experience in matters optical and physiological. 
The following remarks, which he has introduced to give novelty to the old 
edition, will certainly be new to ophthalmic surgeons : Since the rays 
of light which produce the sensation of different colours differ in wave- 
length, or, what is the same thing, since the vibrations they excite in the eye 
differ in rapidity, it follows that if the retina, whilst perceiving the exist- 
ence of the vibrations, be unable to appreciate the difference of their rapidity, 
vision will be unimpaired as to form and position, but differences of colour 
will not be perceived. Such a defect on the misorium of the eye is fortu- 
nately rare, hut not unyrecedentedr This is certainly a mild way of stating 
a defect so common, that candidates for situations as railway guards and 
engine-drivers have been so frequently found to display it, that they are 
now invariably put to the test as to their power of discriminating colours. 
Ophthalmologists know that this condition is by no means unfrequent. 
There are other parts of this book to which we object. Nevertheless, the 
volume is a sound one on the whole, and we can recommend it. 
Tommy Try, and what he did in Science, by C. 0. Groom Napier, F.G.S. 
Chapman and Hall, 1869. Tommy seems to have achieved so high a degree 
of scientific knowledge, at an age when most of the commonplace members 
of the British nursery still maintain an affectionate regard for lolly pops, that 
we fear to push his biography beyond the point at which Mr. Napier’s 
narrative commences. At this tender epoch of his existence, he had reached 
his seventh year, but he had already mastered the Linnean system of 
classification of plants, understood the laws of refraction of light, had been 
stung by a dead medusa, had distinguished the species from another, one 
also duly appreciated, and had experimented with mordants on the dyes of 
some cryptogamic algae.” To pursue Tommy further, would really be to 
travel out of the domain of Popular Science ; so Mr. Napier must excuse our 
leaving his young Crichton to other hands than ours, 
Catiset'ies Scientijiques, 1868. Paris : Rothschild, 1869. Is a year-book of 
scientific facts, and, like all such, is interesting and imperfect. 
