June 26, 1890] 



NATURE 



197 



Yeo's small work fulfils the requirements of a satisfactory 

 book on the subject. It will be found useful for reference by 

 the busy practitioner, and it contains numerous facts, as a 

 rule clearly stated ; and it will perhaps also be found 

 acceptable to the lay public, as, in many parts, the 

 style is more or less popular. The chemistry of food- 

 stuffs is not treated as accurately as it might be. Thus 

 we have " syntonin or muscle fibrin ; myosin, from 

 muscle," placed in separate lines as food-stuffs. In the 

 table (p. 10), "casein" (probably a misprint for ossein) 

 is placed under " gelatigenous substances"; and gelatin 

 is itself considered a "gelatigenous" substance. This, 

 it must be confessed, is a somewhat loose way of de- 

 scribing these substances. 



Dr. Yeo makes the statement (p. i6) that albumen, 

 together with water and salts, is able " alone to support 

 the vital processes," and can " replace in nutrition the 

 fats and carbohydrates." With this statement most 

 physiologists would disagree. Several more instances of 

 somewhat vague statements might be quoted from the 

 work. Milk is considered by all classical writers on the 

 subject a complete or perfect food ; but Dr. Burney 

 Yeo goes further than this, and classes eggs as " the only 

 other complete food afforded by the animal kingdom " 

 (p. 51) : "but when regarded in the light of a complete 

 food, the shell must be taken into account" (p. 69). In a 

 second edition of the work, the physiological and chemical 

 portion wants careful revision. 



In the discussion of the diet in disease. Dr. Yeo is more 

 at home ; and he has set forth the various modes of 

 dietetic treatment of disease in a clear manner. The 

 only fault to be found with this part of the book is that 

 the style is somewhat too diffuse to be of great service to 

 the general practitioner, for whose use the work is 

 evidently chiefly intended. Although we have criticized 

 the loose physiological and chemical statements in Dr. 

 Yeo's work (some of which have been quoted), yet the 

 book will no doubt be found useful by many. 



Fifth and Sixth Annual Reports of the Bureau of Ethno- 

 logy to the Secretary of the Smithsonian Institution. By 

 J. W. Powell, Director. (Washington : Government 

 Printing Office, 1887-88.) 

 These Reports, each of which is presented in a large, 

 well-printed volume, contain the record of much solid 

 and useful work. The first of them — the Report for 

 1883-84— includes an elaborate paper, by Prof. Cyrus 

 Thomas, on burial-mounds of the northern sections of 

 the United States. This is followed by an essay in 

 which Mr. Charles C. Royce tells the story of the official 

 relations of the Cherokee nation of Indians with the 

 Colonial and Federal Governments of North America. 

 In the third paper, Dr. W. Matthews gives an account 

 of what Prof. Powell describes as one of the most illus- 

 trative ceremonies of the Navajo, a tribe formerly widely 

 diffused, and now settled in parts of New Mexico and 

 Arizona. Dr. Clay MacCauley deals with the Seminole 

 Indians of Florida, and Mrs. Tilly E. Stevenson gives a 

 vivid picture of the religious life of the Zuiii child. Of 

 the papers associated with the Report for 1884-85, the 

 first is on the ancient art of the province of Chiriqui, 

 Colombia, by Mr. William H. Holmes. To this excellent 

 paper we have already called attention. It is followed by 

 another, by the same author, on textile art in its relation 

 to the development of form and ornament. Dr.Franz Boas 

 contributes to the volume an instructive and well-arranged 

 paper, in which he sets forth the results of his obser- 

 vation and study of the central Eskimo. Prof. Cyrus 

 Thomas gives some aids to the study of the Maya 

 codices, and Mr. J. Owen Dorsey brings together inter- 

 esting versions of two Osage traditions. These versions 

 are printed in the original language, with an interlinear 

 and a free translation of each, and with explanatory 

 remarks. 



NO. 1078, VOL. 42] 



Light, Heat., and Sound. By Chas. H. Draper, B.A. 



D.Sc. (Lond.). (London : Blackie and Son, 1890.) 

 The syllabus of contents of this little work is that of the 

 elementary stage of the Science and Art Department, 

 some additions being made in the sections on light and 

 Heat in order to bring them up to the standard of the 

 London University matriculation paper. Viewed as an 

 examinational text-book, there is much that is meritorious 

 in the arrangement and general character of the work, 

 the information being conveyed in the disintegrated 

 fashion now so common. We would, however, point out 

 to Dr. Draper that hoar-frost is not frozen dew, but water 

 deposited in the solid form, and that hail is not simply 

 rain-drops frozen as they fall through a cold stratum of 

 air. The questions placed as exercises at the end of the 

 chapters have been selected from papers set at the above 

 examinations, and will serve not only as a test of the 

 student's progress, but as a branch of his mental 

 education worth cultivating. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications, "l 



The Bourdon Gauge. 



Allow me to suggest to such of your readers as are interested 

 in this subject the following experiment. Cut out of cardboard 

 two annular strips, each of somewhat more than a quadrant, the 

 inner radius being say 7 inches, and the outer radius 9 inches. 

 Alongi the middle of each strip — that is, along the circle of 8 

 inches radius — cut the boards half through, so as to render them 

 flexible, and then join the two strips together with gum paper at 

 the inner and outer edges. In this way we obtain a curved tube 

 whose section is a rhombus, and whose curvature is connected 

 with the magnitudes of the angle of the rhombus. The manipu- 

 lation of such a tube gives definiteness to one's ideas, and enables 

 one to recognize that internal pressure, tending to augment the in- 

 cluded volume, and therefore to make the section square, must 

 also cause the curvature of the axis to approach a definite 

 associated value. In this case the deformations are practically 

 by bending, principally, indeed, at the hinges ; and I cannot 

 doubt that in its main features the mechanism of an ordinary 

 Bourdon gauge may be looked at in the same light. 



Rayleigh. 



The Optics of the Lightning Flash. 



In the extract from Mr, Shelford Bidwell's recent lecture on 

 "Lightning" at the London Institution, which appeared in 

 your issue of June 12 (p. 151), I notice the author says that the 

 lightning flash of artists has no existence in nature, and that it 

 is an artistic fiction or symbol. May I venture to trespass on 

 your valuable space to refer to a paper which I had the honour 

 of reading before the Royal Meteorological Society (published in 

 the current Quarterly Journal of the Society) only a few days 

 after the delivery of Mr. Shelford Bidwell's lecture? In this 

 paper I endeavoured to show how the "zigzag" flash so often 

 seen by observers, and frequently depicted by artists, may have 

 its counterpart in nature, quite consistently with the evidence 

 of the photographs of lightning flashes collected by the Royal 

 Meteorological Society. 



I suggested that such an appearance is not the flash itself, but 

 the optically projected image of the flash formed on clouds, not 

 of a smooth surface, but of the rocky cumulus type. The image 

 of the flash takes the angles of the uneven surface and becomes 

 zigzagged. I showed how this might be by casting the photo- 

 graph of a lightning flash — the " streaming " flash — by means 

 of the optical lantern, on model cumulus clouds, made of 

 cotton wool. The "streaming" flash became distorted, and in 

 fact zigzagged, so that it could not have been recognized as the 

 type mentioned. 



" Projection " lightning flashes surely must happen in nature, 

 and might be accounted for in more ways than one. I will 



