28 



SCIENCE 



[Vol. IV., No. 74. 



ture of the language are given. The missionaries 

 have succeeded in improving the material condition 

 of the Fuegians, and have induced some of them 

 to adopt agricultural, pastoral, and other industrial 

 pursuits. 



— In the current volume of the Proceedings of the 

 American academy, Mr. Arthur Searle publishes an 

 elaborate and exhaustive reduction of all the acces- 

 sible observations of the zodiacal light. The paper 

 gives the position of the axis of the cone, and the 

 apparent boundaries of the light, as determined by 

 nearly six hundred and fifty different observations by 

 Jones, Heis, Lewis, and others ; and tables appended 

 give monthly means and other data which summarize 

 the results in a very complete manner. 



Mr. Searle does not indulge in much theoretical dis- 

 cussion as to the nature of the zodiacal light, but he 

 points out tbat the apparent slight deviation of the 

 axis of the cone from the ecliptic is most probably 

 due to the effect of atmospberic absorption, and calls 

 attention to the necessity of more refined methods of 

 observation. He says, — 



" If atmospheric absorption has the importance here assigned 

 to it in the study of the zodiacal light, we cannot expect to de- 

 termine the true position of the light on any occasion by the 

 simple methods heretofore in use. "We must either discover 

 exactly what an observer means by the boundary, and to what 

 extent this boundary will be displaced by given changes of 

 brightness, or we must resort to direct photometric observa- 

 tions. The last course will probably be preferable." 



He suggests a modification of the method employed 

 by Wolf in tracing out the nebulosity about the 

 Pleiades, — a method which consisted essentially in 

 watching the visibility of the threads of a reticle, 

 which disappeared whenever the telescope was di- 

 rected against unilluminated sky. 



In this connection he mentions the interesting fact 

 that the Milky Way appears to be about two magni- 

 tudes brighter than the mean brightness of the sky ; 

 which would mean, of course, that a square degree 

 of the Milky Way gives between five and six times as 

 much light as an average square degree of the rest of 

 the sky. 



His only remark as to the theoretical explana- 

 tion of the zodiacal light is the following : — 



" I have merely to remark, witb regard to the ordinary mete- 

 oric theory, that it gains greatly in simplicity if we dispense 

 with all the imaginary meteoric bodies, or rings, with which it 

 has usually been connected, and retain merely the conception of 

 meteoric dust diffused throughout the solar system. It may be 

 shown mathematically, if we regard the meteoric particles as 

 solids reflecting light irregularly, that an appearance like the 

 zodiacal cone, with an indefinite vertex, would result. On this 

 subject the work of Geelmuyden may be consulted." 



We suppose that by ' diffused throughout the solar 

 system,' he means diffused mainly in the plane of the 

 ecliptic. Indeed, it could be shown, that, if we started 

 with an indiscriminate spherical distribution of mete- 

 oric dust around the sun, the disturbing action of the 

 planets would ultimately convert it into an approxi- 

 mately discoidal distribution in a plane coincident 

 with the mean plane of their orbits. At any rate, it 

 is not easy to see how an indiscriminate distribution 

 should lead to any thing but a glow-cone with a verti- 

 cal axis. 



There can be no question that Mr. Searle has done 

 an important service to science in collecting and edit- 

 ing in so excellent a manner the hitherto scattered 

 observations relating to his subject. 



— Dr. Ernst Haeckel of Jena has been elected a 

 member of the Linnean society for his studies of 

 sponges, Medusae, etc. ; also Dr. Alexander Kowalev- 

 sky of Odessa, for his zoological researches, and Dr. 

 S. Schwendener of Berlin, for his studies in crypto- 

 gamic botany. 



— The twelfth part of Edwards's ' Butterflies of 

 North America' is almost entirely devoted to the 

 polymorphic and wide-spread Lycaena pseudargiolus, 

 two plates with over sixty figures being devoted to it. 

 Such wealth of illustration is exceedingly rare and 

 correspondingly valuable, particularly with the more 

 fleeting and less known early stages. Nineteen col- 

 ored drawings of the larva alone are given; and in 

 execution the illustrations have never been surpassed 

 in the most expensive and careful iconographs. The 

 next number will complete the second series, and we 

 are glad the author shows no sign of discontinuing 

 his costly undertaking. 



— The slight tendency to lateral cutting possessed 

 by rivers, on account of the earth's rotation, and 

 known sometimes as 'von Baer's law,' has had its 

 efficiency denied about as often as it has been granted, 

 by those who have written on the matter ; and, when 

 granted, it has been too often admitted only for 

 streams following meridional directions. 



Mr. G. K. Gilbert contributes a new element to the 

 discussion of 'the sufficiency of terrestrial rotation 

 for the deflection of streams,' in a paper read to the 

 National academy of sciences in April, and recently 

 published in the American journal of science. Tak- 

 ing Ferrel' s measure of the deflective force that comes 

 from the earth's rotation, Mr. Gilbert shows, by a 

 remarkably simple consideration, that its value is 

 not so much in throwing the whole stream against 

 its right bank, as in selecting the swifter threads of 

 the current, and carrying them against the bank ; 

 and, further, that this action will have especially well 

 marked development in meandering streams, where 

 it will aid the cutting on the meanders of right-hand 

 convexity, and diminish it on those of left-hand con- 

 vexity. For the Mississippi, the selective tendency 

 thus determined toward the right bank is nearly 

 nine per cent greater than toward the left ; but it is 

 not stated that the valley form has been noticeably 

 affected by this preference. On Long Island, how- 

 ever, the form of the valleys is clearly controlled by 

 the earth's turning, as was first suggested by Mr. Elias 

 Lewis some years ago, and recently confirmed by 

 Mr. I. C. Eussell. 



The article by Mr. Gilbert advances the question 

 not only by properly applying the law to rivers flow- 

 ing in any direction, but further by giving it a more 

 delicate analysis than it has yet received, with the 

 conclusion that in certain favorable cases the form 

 of a valley may be decidedly influenced by this hidden 

 control. While the result is of interest to physical- 

 geographers, the method of analysis has a wider 



