536 



NA TURE 



[September 29, T904 



important hydroxy! group, readily form mixed crystals. That 

 a definite law does not hold in such cases is shown by the 

 fact that phenol and hydroquinone, which bear the same 

 relation to each other as phenyl salicylate and salicylhydro- 

 quinone, are not perceptibly isombrphous. The results are 

 of importance as indicating a limitation of the cryoscopic 

 method of determining molecular weights. 



Some e.xperiments which are of importance from the 

 standpoint of the theory of dyeing are described in the 

 Proceedings of the Vienna Academy of Sciences .(No. 15) 

 by Prof. AV. Suida. On exposing several finely 

 divided natural silicates to the action of coal-tar dyes, 

 it was found that those silicates which were of an 

 acid nature, containing free hydroxy! groups, were per- 

 manently dyed by the basic dyes of this series, whilst acid 

 dyes were without action. Similarly, hydrated silicic acid 

 readily absorbs the same colours, whilst silicic anhydride has 

 no affinity for them. When kaolin is used, the different 

 colour-bases combine with it in equivalent proportions, 

 probably to form colour-salts, the original acid in the dye 

 becoming attached to constituents of the clay. Similar 

 results were obtained with potato-starch, and the general 

 conclusion is drawn that the process of dyeing with basic 

 colours is far more chemical than physical in its nature. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in October : — 

 Oct. I. 7h. Mercury at greatest elongation, 17° 54' W. 



5- 7h. 45m. to 9h. 7ni. Transit of Jupiter's Sat. III. 

 7. I5h. Moon in conjunction with Mercury. Mercury 



1° i' N. 

 12. iih. om. to I2h. 24m. Transit of Jupiter's Sat. III. 

 15. Venus. Illuminated portion of disc = 0'897, of 

 Mars = o'956. 



18. iih. om. Jupiter in opposition to the Sun. 



19. I4h. 13m. to I5h. 42m. Transit of Jupiter's Sat. III. 

 19-21. Epoch of October meteors (Radiant 92°+ 15°). 



loh. 8m 

 6h. 57m. 

 loh. om. 

 Jupiter 

 6h. 37m. 



Minimum of Algol (0 Persei), 



Minimum of Algol (B Persei). 



Moon in conjunction with Jupiter. 



° 34' N. 



Jupiter's Sat. IV. in superior geocentric 

 conjunction. 

 26. l6h. 48m. to I7h. 25m. Moon occults 7 Tauri (mag 

 3-9). 



Explanation of the Martian a.nd Lunar Canals. — Prof. 

 W. H. Pickering, writing to No. 7, vol. xii., of Popular 

 AsTronomy, offers an explanation of the formation and 

 variation of the Martian canals which is based on their 

 analogy to the similar features seen on the lunar surface. 

 Whilst accepting the vegetal origin so ably supported by 

 Mr. Lowell, Prof. Pickering finds the theorv of artificial 

 pumping suggested by that observer difficult to realise. 



Instead of this, he supposes' that the lunar canals, and 

 hence, by analogy, those observed on Mars, are simplv 

 lines of volcanic action on the surface where the crust is 

 weakened, and therefore is easily cracked by the internal 

 stresses put upon it by the action of the heated interior. 



This theory is supported by his observations that the 

 canals, and also the lakes from which they appear to radiate, 

 are dotted by small craterlets and are so symmetrically 

 arranged about the craterlets as to suggest a causal relation 

 between the two phenomena. Analogous formations are 

 common in terrestrial volcanic districts ; for example, in the 

 2000 mile stretch of volcanoes which occurs in the Andes. 



This theory does not require the transference of water 

 and carbon dioxide along the canals, but supposes that thev 

 issue directly from the interior along the whole length of 

 each fissure, and in conjunction with sunlight promote the 

 growth of vegetation. Owing to the rarity of the atmo- 

 sphere, Prof. Pickering suggests that the vapours would 

 not ascend on their emergence, but w-ould quietiv roll down 

 the slopes of the craterlets, or " lakes," and canals, thereby 



NO. 1822, VOL. 70I 



sufficiently irrigating the immediate vicinity to produce the 

 vegetation. 



Further Observations of the Recent Perseid Shower. 

 — Communications from American observers confirm the 

 comparative richness of the recent display of Perseids. 



At Wilmington (N.C.) Mr. E. S. Martin saw between 

 25 and 30 Perseids per hour between g p.m. and 12 p.m. 

 (local M.T.) on the nights of August 10 and 11, although 

 very few were seen on August 12 and 13, and none on 

 August 14. 



.■\t Barre (N.Y.) Mr. W. Wetherbee saw 154 meteors, of 

 which 116 were Perseids, in less than three hours on the 

 eve of August 11. He remarked that many of the Perseids 

 appeared in pairs the components of w^hich travelled in 

 parallel paths and had equal magnitudes. According to 

 this observer, the radiant has moved westward, and appeared 

 to be near to the star 1 Persei. One extraordinarily bright 

 Perseid appeared in Aquila, and left a trail 10° long which 

 lasted for about four minutes (Popular Astronomy, No. 7, 

 vol. xii.). 



Position of Saturn's Ninth Satellite. — A telegram 

 from Prof. E. C. Pickering, published in No. 3969 of the 

 Astronomischc Nachrichtcii, announces that Prof. Barnard 

 observed Phcebe, Saturn's ninth satellite, on September 

 12-6916 (G.M.T.). The apparent position at that time was 

 as follows : — 



a = 2ih. 12m. 295s., 5= — 17° 25' 55". 



The motion of the satellite was south-west, whilst the 

 magnitude was 16 7. 



Distribution of Nebul.i in Rel.vtion to the Galaxy. — 

 In No. 3969, of the Astronomischc Nachrichien Dr. C. 

 Easton discusses the distribution of the nebula: in regard 

 to the galactic system. 



Commencing with the usually accepted statement that 

 the nebulae not only occur some distance from the Milky 

 Wav, but that they actually tend to congregate about the 

 galactic poles, he confirms this, from observational data, 

 for the northern hemisphere, but questions its truth for the 

 southern hemisphere. He further states that the accepted 

 notion that it is simply the lack of observations which 

 accounts for the apparent scarcity of nebulae in the southern 

 hemisphere is not founded on fact. If it were true, then 

 that part of the northern galactic zone which lies south 

 of the equator should apparently contain fewer nebulae than 

 that part which is above, because it has not been so well 

 observed. The following figures show that although this 

 is true for the faint nebula;, which with the planetary 

 nebula are placed in the category of " green nebulae," in 

 the case of the bright {I.e. " white ") nebulae the inverse is 

 true : — 



Northern Galactic Zone. 



S. of the equator N. of the equator 



■ ■■ 754 '043 



... i::2 71 



Faint nebula? 

 Bright nebula2 



This leads to the conclusion that the nebuI.TS in the 

 southern hemisphere are not arranged in the same manner 

 as those in the northern. 



Several other interesting points are developed by Dr. 

 Easton in his paper, and are supported by the tabulated 

 observational results which he gives. One other important 

 conclusion at which he arrives is that the faint nebula are 

 allied, as regards their phase of development, to the steHar 

 conglomerations of the galaxy and occur in the same 

 regions, whilst the bright (V.i?. " true") nebula? are 

 similarly allied to the sparsely distributed non-galactic stars. 



ASTRONOMY AND COSMICAt PHYSICS AT 

 THE BRITISH ASSOCIATION. 



GREAT vitality was shown in this subsection, and three 

 mornings and one afternoon were hardly sufficient to 

 get through the rather large programme. The meetings 

 were welV attended, and were of particular interest, since 

 many distinguished foreigners were present, several of 

 whom attended at Cambridge in consequence of the meet- 

 ing there of the subcommittee of the International Meteor- 

 ological Committee which was appointed at Southport last 



