May 19, 1893.] 



SCIENCE. 



277 



directly as the number of sun-spots visible. Now, it there were 

 an intimate connection between the two classes of ijhenomena, 

 the appearance of an area of great solar disturbance at the eastern 

 limb, as is occasionally the case at the time of a minimum, should 

 give very marked auroral displays, whereas it is quite certain 

 that the coincidence is not so marked at these times (where the 

 element of " chance " is reduced) as at the time of a maximum ; 

 is this not so? 



Auroras are, or are not, an effect of sun-spots on the sun's 

 eastern limb. I spent fourteen months in Hudson's Strait, and, 

 to my knowledge, during the auroral season from 50 to 75 per 

 cent of our clear nights (and clear nights were a peculiarity of 

 the latitude in winter) had auroral displays. Assuming two such 

 solar areas as required constantly on the sun, and representing 

 the term "eastern limb"' by twenty- four hours, we hare a vastly 

 larger number of auroras unaccounted for than this theory ac- 

 counts for. 



Quoting from Dr. Veeder's letter to Science, April 28, he says : 

 "When, however, this area was at the eastern limb, from Jan. 

 7-11, although it had not yet developed spots, and was the seat of 

 brilliant faculae only, . . . great magnetic storuis "were "in 

 progress and auroras . . . reported in high latitudes." 



I never saw, nor do I expect to see, the eastern or western 

 limb of the sun when faculse are visible to ordinary powers, when 

 they were not more distinctly "brilliant" there than elsewhere. 

 If this condition can be taken as a fulfilment of this theory, it is 

 evident that the theory is beyond argument. 



This quotation furnishes the required instance " in which an 

 aurora appeared in the absence of ivell-defined solar conditions," 

 for, according to the evidence supplied, "a great magnetic storm " 

 was in progress from Jau. 7-11, whereas I feel certain that Dr. 

 Veeder cannot claim that an area represented by five days' solar 

 rotation (Jan. 7-11) could possess (in fact, bis words show it did 

 not possess) well-defined solar conditions of the nature required. 



Sun-spots ' have been a special object of study at this observa- 

 tory since its institution. It is safe to say that soaielhing is 

 known of their nature and origin, but that it is as nothing to that 

 which remains to be investigated. It is possible to allow fanci- 

 ful attributes to this little-known agency, which will account for 

 any theory we may be pleased to conceive, but, treated in accord- 

 ance with any known dynamical law, there seems to be no way 

 of accounting for the peculiar action of this force, which is not 

 equally applicable to its jjosition at the western limb. It seems 

 evident, from the nature of a sun-spot's formation, that the force 

 employed is exerted in a vertical direction ; it would be reasonable 

 to expect that the resulting maximum effect should lie evident, 

 if at all, in the same direction; not horizontally, as this theory re- 

 quires. 



Assuming the solar force to be an "electro-magnetic" one, any 

 resulting auroral development should bear a fixed relation to the 

 line joining the source of energy with the earth's centre and the 

 plane of rotation of the earth. If this is a fact, it is quite evident 

 that points widely differing in longitude on the earth's surface 

 will experience similar effects, as the earth's diurnal motion brings 

 them successively under this influence, after a time-interval 

 almost infinitely less than that represented by the difference of 

 longitude of the two points considered. No one will surely claim 

 that this is even approximately the case. 



Again, " cosmical dust and debris " is not conclusively present 

 in the "zodiacal light." Even accounting for the origin of the 

 zodiacal light in this way, it is observationally evident that the 

 rest of interplanetary space is not so filled, for this light is only 

 visible as an appendage to the sun, in certain fixed directions; 

 elsewhere the absence of the light proves that this " dust and 

 debris " is not symmetrically disposed about the sun. Admitting, 

 for the sake of argument, that interplanetary space was filled with 

 (his dust and debris, the lapsed aaons of planetary existence with 

 liie countless orbital revolutions of the planets themselves must 

 have swept out, as the masses of the planets must have aggregated 

 to themselves, the last vestige of such dust and debris, leaving 

 vast intervals without this assumed conducting material. 



' " Sun-Spot3 : Their Maximum and Minimum Periods and Zones of Great- 

 est Frequency." Eead before the Royal Astronomical Society, April 13, 1882. 



I should be pleased, and I think it would be a matter of more 

 than personal interest, if Dr. Veeder has the time, in what I know 

 to be a very busy life (setting the "limit" I have suggested), if 

 he would, from out the fund of information in his possession, see 

 how far the element of "chance" enters into this question, not 

 admitting too much of the suppositional when sun-spots fail at 

 the required period by the substitution of "faculse," and at the 

 same time show a comparison of coincidences through a semi- 

 period, at least, of solar activity. W. A. Ashe. 



The Quebec Observatory, May 6. 



BOOK-REVIEWS. 



The Earth's History. An Introduction to Modern Geology. By 

 R. D. Roberts. New York, Chas. Scribner's Sons. 1893. 

 Maps and illustrations. 370 p. 12°. $1.50. 



This volume is one of a series now being published in England 

 by Murrray and in this country by the Scribners, as an outcome 

 of the popular University Extension movement. The prospectus 

 states that " the aim of these manuals is to educate rather than 

 inform. In their preparation, details will be avoided except when 

 they illustrate the working of general laws and the development 

 of general principles ; while the historical evolution of both the 

 literary and scientific subjects as well as their philosophical sig- 

 nificance will be kept in view." 



The author of the present volume has been successful in car- 

 rying out this plan, for without being detailed he presents the 

 broader aspects of the science in a familiar and pleasing manner. 

 In the chapter on the "Agents of Destruction," he refers par- 

 ticulai-ly to the Grand Canon region, where the phenomena of 

 denudation are shown on such a magnificent scale. This is fol- 

 lowed by chapters on the extent of the destructive operations in 

 Nature, and these, in turn, by other chapters on the construction 

 of land. The constructive agents are grouped under the three 

 heads of deposition, movements of the crust, and addition by ex- 

 trusion from the interior. There are interesting accounts of 

 shallow-water deposition, of calcareous deposits, such as coral 

 reefs, and of deep-sea deposits. The author does not commit 

 himself in regard to the origin of atolls, referring to Darwin's 

 theory of subsidence, but not discussing others that have been 

 advanced. An interesting account is given of the formation of 

 Monte Nuovo in 1538 and of the destruction of Krakatoa in 1883. 



The last part is devoted to the ' ' Evolution of Land Areas," and 

 we have here the application to geological phenomena of the 

 principles enunciated in the first parts. Two chapters deal with 

 the evolution of the British Islands. Altogether the volume gives 

 an excellent exposition of geological phenomena and must serve 

 as a useful compend to all who desire a knowledge of the princi- 

 ples without having to wade through a mass of details concern- 

 ing the subject. For these details other volumes must be con- 

 sulted. Joseph F. James. . 



Washington, D. C, May 3. 



Public Health Problems. By John P. J. Sykes. The Contem- 

 porary Science Series. New York, Charles Scribner's Sons. 

 8°. 



The multiiDlication of books relating to public health may per- 

 haps in itself be encouraging, but the fact that the quality in no 

 way keeps pace with the quantity is quite the reverse. The book 

 before us covers a wide field — from " heredity " to "dwelling- 

 houses" — but conveys, whether rightly or wrongly, the impres- 

 sion of being in the main the result of a "cram." The chapter 

 on heredity, for example, opens with this remarkable statement, 

 " The Darwinian theory of natural selection has given promi- 

 nence to two schools of evolutionists, the one attributing evolu- 

 tion solely to selection, and the other, whilst not denying the ef- 

 fects of selection, valuing — perhaps over-valuing — theeffectsof 

 heredity " (p. 8). If the reader be fairly conversant with modem 

 biological literature and be in a somewhat cynical mood he will 

 at least derive some amusement from the rest of that chapter. 



It is perhaps unfair to single out the chapter on heredity for 

 especial criticism since the subject is rather remote from the 

 author's main theme. We regret, however, to be obliged to point 



