196 



NA TURE 



[December 31, 1891 



forward ; and, in consequence, the writer of " Colour 

 Blindness and Colour Perception " regrets that he has 

 to condemn his test. Probably the test will survive the 

 condemnation. Already, according to the figures of Dr. 

 Joy Jeffries, of Boston, some 180,000 persons have by 

 its means been tested expeditiously and effectively. The 

 mention of the American authority on the subject 

 emphasizes the fact that the name of one whose labours 

 in physiology and optics place him in the front rank of 

 English physicists is omitted from the list of English 

 authorities on the subject. Brewster, Herschel, Tyndall, 

 Maxwell, Pole, Abney, Rayleigh, Galton, Nettleship, 

 Bickerton, Frost, and Hogg are recognized as having 

 added to our " knowledge of colour blindness and the 

 dangers arising from the defect." The name of Dr. 

 Brudenell Carter does not appear in the list ! The 

 omission is so glaring when the well-known character of 

 Dr. Carter's contributions to the lore of colour blindness 

 is considered, that there must be some reason for it. 

 Doubtless it is because Dr. Carter has been guilty of the 

 heinous crime of championing the theories of Young and 

 Helmholtz that Mr. Green refuses to recognize him as a 

 contributor to our knowledge of the subject under dis- 

 cussion. Dr. Carter once said, in the course of one of the 

 Cantor Lectures : " I read somewhere, and have vainly 

 endeavoured to find again, a denunciation of the 

 'fallacies of the Young-Helmholtz theory.'" We re- 

 commend "Colour Blindness and Colour Perception" 

 to his attention. The so-called fallacies he will there 

 find completely exposed and shattered in a manner 

 most refreshing, and perfectly satisfactory — at least to 

 Mr. Green. 



Careful study of Mr. Green's work forces upon one the 

 conclusion that the theories of Young and Helmholtz are 

 ''fallacies" for the simple reason that he has failed to 

 understand them aright. Holmgren's tests are no tests 

 because their principle is opposed to the unscientific 

 elaborations of Mr. Green, 



An extension of the field of research, together with an 

 honest attempt to understand the " fallacies " of Young 

 and Helmholtz, will, we are certain, induce Mr. Green to 

 remove from his book many of its errors and absurdities. 



■ A METEOROLOGICAL GUIDE-BOOK. 

 Instructions Meteorologiques. Par A. Angot. Troisieme 



Edition. (Paris : Gauthier-Villars et Fils, 1891.) 

 T^HE " Instructions Metdorologiques," which is the 

 -L official guide-book for meteorological observers 

 in France, has long been known as a model work of its 

 kind, distinguished by great clearness and sufficiency of 

 detail, while avoiding prohxity. The third edition, lately 

 published, has been revised and extended by M. Angot, 

 whose name is a sufficient guarantee that it maintains the 

 high standard of the original work. 



The subject-matter of the present edition has been 

 increased by nearly one-half. One of the chief additions 

 is the description of some of the simpler self-recording 

 instruments, which, it is stated, are coming into general 

 use at the minor French observatories— viz. the sun- 

 shine recorder, the recording aneroid, an autographic 

 thermometer on the Bourdon principle constructed by 

 NO. I 157, VOL. 45] 



MM. Richard Fr^res, and an autographic hair-hygro- 

 meter. The section on cloud observation has been 

 recast in accordance with the classification proposed 

 by MM. Hildebrandsson and Abercromby, and, under 

 the heading of " Phcnomenes Optiques," halos and the 

 aurora borealis are described. The more common ap- 

 pearance of lunar and solar coronas, though mentioned, 

 is not specially noticed in this section. In a book in- 

 tended for the instruction of beginners, we think it would 

 have been well to point out the distinction of coronas and 

 halos, since, in our experience, the latter are not infre- 

 quently recorded by inexperienced observers, when the 

 former have been the phenomena really observed. 



Another subject, treated of for the first time in this 

 edition, is the computation of elevations from the baro- 

 metric readings, and also from those of the hypso- 

 metrical thermometer, the use of which is described at 

 length. In the appendix are given tables for facilitat- 

 ing the reduction of the observations of both classes of 

 instruments. 



The patterns of the various instruments, thermometer- 

 shelters, &c., approved by the author of the " Instruc- 

 tions," differ in many respects from those generally 

 preferred by English observers, and in such matters 

 there will, of course, be differences of opinion. The 

 French thermometer-screen, represented on pp. 32 and 

 33, affords, in our opinion, a better exposure than the 

 Stevenson screen adopted by the Meteorological Societies 

 of England and Scotland, but seems hardly to protect 

 the instruments sufficiently in stormy weather ; while the 

 simpler form represented on p. 35 seems quite inadequate 

 in the latter respect, and the method of suspending the 

 maximum and minimum thermometers somewhat flimsy 

 and insecure. 



In the text of the work we find little or nothing to 

 which we could take exception, but we think one or two 

 of the figures are open to improvement. The close 

 proximity of the wet and dry bulb thermometers repre- 

 sented in Fig. 16 is hardly compatible with accurate 

 registration of the humidity of the air ; and surely the 

 wind-vane represented on p. 73, on the slope of a roof at 

 some indefinite distance below the ridge, is scarcely in an 

 ideally good position, and such as should be put before 

 learners as a standard model for imitation. We would 

 also suggest that, in future editions, a simple forrri of 

 nephescope, such as Marid Davy's, should be described, 

 together with directions for observing the movement of 

 the clouds. It has long been a matter of surprise that a 

 class of observations so important in themselves and so 

 easily made has been so generally ignored by the writers 

 of such manuals as the present. 



OUR BOOK SHELF. 

 Chambers's Encyclopcedia. New Edition, Vol. VIII. 

 (London and Edinburgh : W. and R. Chambers, 1891.) 

 We are glad to welcome a fresh instalment of this 

 admirable edition of Chambers's well-known Encyclo- 

 paedia. It deals with the subjects indicated by 

 words extending from " Peasant " to " Roumelia." Sub- 

 jects of scientific interest have, as usual, been intrusted 

 to writers who know how to present concisely and clearly 

 the latest results of research. A clear account of the 

 phonograph is given by Mr. Thomas A. Edison ; and 



