Oct. I, 1874] 



NATURE 



443 



each magnitude. Notwitlistanding the difficulties which are 

 incident to this method, due to inevitable errors of observation 

 and comparison, Littiow believed that a sufficient degree of 

 uniformity was demonstrated to justify faith in the general theory 

 that there is a considerable degree of uniformity in the distances 

 of the fixed stars within his investigation, and that there is 

 . vvanant for applying his formulas — the results of his research — 

 to regions outside of his limits. Discussing the numbers in 

 Argelander's catalogue assorted by units as far as the eighth 

 magnitude, he obtains the fraction 0423 for the ratio of 

 brilliancy between stars of two successive magnitudes ; assorted 

 by half units, the fraction is (including SA) o'43l. Each compu- 

 tation gives the distance of a star of the eighth magnitude as iS, 

 that of a star of average first magnitude being taken as a unit. 

 The discordances between the results given by the empirical 

 values of the formula and those from the enumeration of the 

 catalogue are large, amounting to 39 per cent, for stars of the 

 fourth, and 44 per cent, for stars of the ninth magnitude. 



The recent completion of our Argentine Uranometry deter- 

 mines the actual magnitudes for all stars easily visible to the 

 naked eye throughout the heavens. Prof. Gould thinks it im- 

 probable that the error of individual magnitudes exceeds the 

 tenth of a unit. Prof. Heis has revised and extended Argelander's 

 work to the nearest third of a unit for all stars visible in Central 

 Em'Ope with the naked eye, his lowest limit being b\. The 

 Argentine work furnishes similar data with respect to the stars 

 in the southern hemisphere. Prof. Gould has carefully studied 

 the results of Liltrow's enumeration, is convinced of the accuracy 

 of his computations, and accepts his formula as the best obtain- 

 able. Prof. Gould has extended a similar comparison to all the 

 stars in the heavens of the sixth magnitude, using the numbers 

 and magnitudes furnished by the uranometries, and obtains the 

 value of the constant as o'482. The accordance of this with 

 observations may be judged from the following table : — 



NUMBER OF FIXED ST.\RS. 



Miigni." 



40S 



632 



i.=S9 



— _ ... _ 20,582 



— — ... — 35,601 



— _ ... _ 61,582 



The columns under " Argelander " give the numbers obtained 

 respectively by enumeration and by the formula thence deduced, 

 from the Durclnuttstaung, and, of course, apply only to the 

 northern hemisphere. The columns under " Uranometries" are 

 deduced from lleis's Atlas Calcstis for the northern sky and 

 from the Argentine Uranometry ior the southern. Under the 

 " Whole Sky " the first contains the sum of northern and southern 

 stars from the columns immediately preceding ; the second the 

 numbers computed on the hypothesis of uniform distribution in 

 space and equal brilliancy. Comparing these numbers with 

 those obtained from the Diirchmustcntng, the latter must of 

 course be doubled. 



The carefully determined numbers of bright stars from the 

 Uranometry afford no greater support to the hypothesis than 

 those obtained from the Dmxhmnslcning. While a general 

 similarity between the numbers of count and of theory is apparent, 

 the accordance is sufficient to warrant deductions which are not 

 essentially vague. Still the approximate accordance, as far as 

 it goes, may furnish us with a constant magnitude ratio for crude 

 estimates in cosmical inquiries . 



If we assume, according to hypothesis, an equal number of 

 stars in each hemisphere, there are altogether not less than 

 15,300 stars as bright as the seventh magnitude. But since the 

 count indicates an excess of bright stars in the northern sky, 

 there may be a thousand more, as given by the formula. The 

 numbers of the Dwilimusleniiii; imply the existence of over 

 200,000 stars as bright as the ninth magnitude, though the 

 magnitudes of faint stars in that work seem given on the aver.age 

 a little loo bright. The average distance of ninth magnitude 

 stars seems to exceed 25. The manifest agglomeration of faint 



stars in the Milky Way shows the inapplicability of the hypo- 

 thesis to stars fainter than a certain magnitude. The limit of 

 applicability is probably considerably beyond stars of the seventh 

 magnitude or distances twelve times the average of first magni- 

 tude stars. There is no contradiction in all this to the well- 

 known fact of accumulation of brighter stars in certain regions. 



With regard to the belief that the number of stars of any 

 given magnitude dimmishes with their distance from the Milky 

 Way, Prof. Gould says that in the clear atmosphere of Cor- 

 doba the existence of a bright stream of stars was very notice- 

 able, including Canopus, Sirius, and Aldebaran, with the most 

 brilliant ones in Carma, Columba, Canis Major, the Pleiades, 

 &c., and skirting the Milky Way on its preceding side. On the 

 opposite side of the galaxy the same was tnie, the bright stars 

 fringing it in a stream that leaves it at Alpha and Beta Centauri, 

 comprises the constellation Lupus and a great part of Scorpio, 

 and extends onward through Opliiucus toward Lyra. Thus a 

 great circle or zone of bright stars seems to gird the sky, inter- 

 sectmg with the Milky Way at the Southern Cross, but far more 

 conspicuous on the other. The northern intersection of this zone 

 Prof. Gould finds in Cassiopeia, which is diametrically opposite 

 to the Southern Cross. The right ascension of the northern node 

 is oh. 50 m. ; the southern 12 h. 50 m. ; the declination about 

 60°, and vei-y near the points where the great circle of the 

 Milky Way has its maximum decUnation. The inclination of 

 this stream of stars to the IMilky Way is about 25° ; the Pleiades 

 occupying a point just midway between the nodes. Prof. Gould 

 after making this discovery found that it had been partially an- 

 ticipated by Sir John Ilerschel, so far as the recognition of a 

 portion of the zone was concerned. The two classes of con- 

 siderations — the approximate method furnished by the hypo- 

 thesis of an equable distribution of stars, and the existence 

 of a well-marked zone of very bright stars as much in- 

 clined to the Milky Way as the equator is to the ecliptic, may 

 assist in determining the position of our sun with reference to 

 its own cluster, that of the cluster itself, and the scale of dis- 

 tances between its constituent stars. 



Prof. Wright read two papers on cognate subjects, one On the 

 usi: of Natural Twin Crystals of Quartz in the construction of 

 Polarixopes, and On the nature of the Zodiacal Light ami the 

 distribution of matter which occasions it. — Prof. Wright gave 

 reasons for doubting whether the hypothesis of bodies rotating 

 around the sun in all directions, and within the orbit of the earth, 

 will account for the zodiacal light. The observed form of the 

 zodiacal light is consistent with the supposition that the reflecting 

 bodies move in long orbits — i.e., orbits of great eccentricity. 



Small Brains in Tertiaiy Mammals. — Prof. Marsh compares 

 the mammals of the Eocene, Miocene, and Pliocene, with the 

 result that in the case of the animals observed, Dinoceras and 

 Brontotherium, a veiy distinct and remarkable development of 

 brain from the lower to the higher formations. 



Summer Dormancy of Butterfly Lankv, by Prof. C. V. Riley, 

 of St. Louis. — In this paper the author, referring to Mr. S. PI. 

 Scudder's paper in the American Naturalist for Sept. 1S73, gave 

 the results of his observations on the larvce of Phyciodes nycteis, 

 some of which appear to remain in a dormant state through the 

 summer and succeeding winter. 



The Disintegration of /blocks, by Prof. T. Steiry Hunt, of 

 Boston. — This subject the speaker had noticed briefly in a com- 

 munication to the Association last year on the geology of the 

 Blue Ridge. The change of the rocks in question is a chemical 

 one, which is the most obvious in the case of crj'stalline rocks ; 

 the feldspar loses its alkalies and part of its silver, being changed 

 into clay, and the hornblende its lime and magnesia, retaining 

 its iron and peroxide. From this results a softening and decay, 

 to greater or less depths, of the strata, so that while they still 

 retain their arrangement, and are seen to be traversed by veins 

 of quartz and metallic ores, the strata are often so much changed 

 to depths of one hundred feet or more from the surface as to be 

 readily removed by the action of the water. 



Fog Signals and Transmission of Sound, by Prof. Joseph 

 Henry, of Washington. — Prof. Henry does not exactly accept 

 the deductions recently made by Prof. Tyndall, having himself 

 obser\'ed a large number of similar phenomena, and attributing 

 them to refraction, not absoiption, of sound by wind and other 

 causes. Prof. Henry found Tyndall's explanation, that a mixed 

 atmosphere absorbed sound, inadequate to explain the facts. The 

 practical interference, and therefore the practical absorption, 

 must be very inconsiderable compared with the volume of sound. 

 In the c.rse of the syren, such is the intensity of the sound that 

 it would cause sand to dance on a stretched membrane at a dis- 



