14 



♦ KNOWLEDGE ♦ 



[Jolt 4, 1884. 



"A LADY " has received^ many letters relating to the 

 rational dress ia that form wliioh cannot be distinguisl\ed 

 from ordinary dress, but is as light, or almost as light, as 

 the more obtrusive divided skirt. We believe that pat- 

 terns will before long be provided for those who care to 

 obtain them ; wheu ready they will be advertised in these 

 columns. 



THE FACE OF THE SKY. 



FnoM JuLV 4 TO July 18. 

 By F.R.A.S. 



THE sun continues to provide daily work for the observer, and 

 should be examined with the telescope whenever the sky is 

 clear. The aspect of the night sky will be found delineated in 

 TUap YII. of " The Stars in their Seasons," twilight, however, 

 still persisting all night long. Mercury is a morning star to-day, 

 but comes into superior conjunction with the sun at 5 a.m. on the 

 13th, upon which, of course, he becomes au evening star. Venus 

 will be in inferior conjunction with the sun at 2 a.m. on the 12th. 

 Every effort should be made by the student to obsen-e her in the 

 telescope at and about this time, as she presents one of the most 

 exquisite and all-repaying spectacles that it is possible to conceive, 

 shining as a hair-like semi-circular thread of silver in the glare of 

 sunlight. Moreover, under really favourable atmospheric circum- 

 stances, and a sutEciently-constricted telescopic field, the observer 

 may hope to see the dark body of the jilanet embraced by this 

 wonderful silver hair of light, like " the old moon in the new moon's 

 arms." At noon on July 11th Venus will bo approximately -t" 51', 

 or about 10 diameters of the sun, south or below his centre. This 

 juay help the beginner to fish her up with a telescope not mounted 

 equatorially. Xo other planets are visible at present. Three occul- 

 tations of stars by the moon occur during the fourteen days 

 covered by these notes. The first happens on the night of 

 the 11th, and is one of the fourth mag. star 9 Aquarii, which 

 will disappear at the moon's bright limb at llh. 18m., at an angle 

 of 07° from her vertex. It will re-api>ear at her dark limb at 

 12h. 29m. p.m. at a vertical angle of 271'°. On July 15, the fourth 

 mag. star o Piscium will disappear at the bright limb of the 

 moon at 12h. 53m. p.m., at an angle from the vertex of 60°. It 

 ■will re-appear at 51m. after 1 the next morning, at an angle of 264' 

 from her vertex. Lastly, on the IGth, rather more than half-an- 

 hour before the moon rises, she will have occulted 31 Arietis, a star 

 of the sixth magnitude. Later, at llh. 55m. p.m., this star will re- 

 appear at the moon's dark limb at a vertical angle of 246'. When 

 our notes begin, the moon is in Libra ; but at two o'clock this after- 

 noon she leaves it for the narrow northern strip of Scorpio. She 

 takes until one o'clock to-morrow morning to cross this, and then 

 enters Ophiuchus. This she quits at 10 p.m., on the 6th, for Sagit- 

 tarius. Her passage through Sagittarius occupies until 11 a.m. on 

 the 9th, at which hour she passes into Capricornus, the boundary 

 between which and Aquarius she crosses at 5 a.m. on the 10th. 

 About 3 a.m. on the 13th, she leaves Aquarius for Pisces, and 

 ■continues to travel through that large and straggling constellation 

 until she enters Aries, at 5 a.m., on the 16th. At 8 p.m., on the 

 17th, she moves into Taurus, which she is still traversing when 

 tiese notes terminate. 



The "Researches on Astronomical Spectrum Photography" of 

 the late lamented Professor Henry Draper have just been repub- 

 lished, with au introduction and description of the apparatus by 

 Professor C. A. Young, and measurements and description of the 

 plates by Professor E. C. Pickering, together with reprints of Dr. 

 Draper's various papers on the subject. Apart from its enduring 

 importance as a record of a mass of valuable physical facts, and as 

 containing a history of the infancy and youth of Stellar spectral 

 research, this posthumous volume of the great American physicist 

 possesses a high degree of interest, as showing what an enormous 

 amount of scientific work of the highest value could be performed 

 by an absolutely unsubsidised obser\-er. Professor Draper would 

 have felt that he was inflicting as much degradation on science as 

 he would have brought upon himself personally had he gone whining 

 to Congress for " endowment." Like our own Faraday, though, he 

 "had no time to get rich;" and his name will assuredly live in 

 honour when those of the men whose idea of science is narrowed 

 to that of their own pecuniary advancement will have long sunk 

 into oblivion. 



' Let Knowledge grow from more to more." — Alfred Tekxtsor. 



Only a small proportion of Letters received can possibly be in- 

 serted. Correspondents must not le offended, therefore, shouid their 

 letters not appear. 



All Editorial communications should le addressed to the Editor of 

 Knowledge ; all Business communications to the Publishers, at the 

 Office, 74, Qreat Queen-street, TT.C. If this is not attended to 



DELAYS ARISE FOR WHICH THE EDITOR IS NOT RESPONSIBLE. 



All Remittances, Cheques, and Post Office Orders should be made 

 payable to Messrs. Wtuan & Sons. 



The Editor is not respomille for the opinions of corresponden'.s. 



No COMMUNICATIONS ABE ANSWERED BY POST, EVEN THOUGH 8TAHPBD 

 AND DIRECTED ENVELOPE BE E^'CLOS£D, 



LARGE CELLS FOR ELECTRO DEPOSITION. 



[1322] — Mr. Slingo's last paper on "Electro-plating," in which 

 he refers to the expense of rectangular baths made of pottery, re- 

 minds me of my own experience in the early days of electrotyping 

 (about 1845-6). I made two large tanks for depositing copper 4ft. 

 long, 2 1 ft. wide, and 2 J ft. deep. They were of common deal, put 

 together in the usual way, by dove-tailing; but were double. 

 The outer tank was about 1 in. thick ; the inner tank was made of 

 1 in. wood, with outside dimensions i in. less all round than the 

 inside dimensions of the outer trough. On the bottom of the out- 

 side tank were a few small blocks about 1 in. square and i in. thick. 

 Thus, when the inner or lining tank was put in its place, resting on 

 these blocks there was a space on all sides and the bottom of J in. 

 thickness between the inner and outer tank. To keep the lining 

 accurately in the middle, I put temporary strips i in. thick down 

 each side. 



This being arranged, I poured melted pitch into the i-inch space, 

 only in sufficient quantity, at nrst, to flow over the bottom and rise 

 a few inches above the sides, as I anticipated a floating up of the 

 whole of the inner case if all the liquid were added at once. On 

 the following day, after this first pouring had cooled and solidified, 

 I poured more, suSicient to fill the ^-inch space completely, and 

 then left the whole to solidify. Then followed a curious illustra- 

 tion of the viscosity of the apparently solid pitch. The inner case 

 gradually rose day by day, threatening to wreck the whole arrange- 

 ment. I filled it "with water, and it gradually sunk until it rested 

 on the cheek blocks, where it remained when subsequently filled 

 with the copper solution. 



The second compound trough was similarly treated, and both were 

 used by myself for two years without leakage, and long afterwards 

 by my successor. The copper solution soaks through the porous 

 wood of the inner lining, but is effectually resisted by the sur- 

 rounding wall of pitch. I do not recommend this for silver solu- 

 tions ; the cyanides are alkaline, and will act upon the pitch, and 

 thus, in course of time, the solution will become polluted by a solu- 

 tion of the pitch. This does not happen to the acid copper solution. 

 Now that paraffin wax is obtainable for 6d. per pound, I recommend 

 it as a substitute for the pitch, and have no doubt that cells thus 

 constructed will be found available for all kinds of solutions that 

 are used cold. W. Mattiec Williams. 



COLOUK-LANGCAGE. 



[1323]— The construction which Mr. Titchener (question 1320) 

 puts on my sentence is justified by the wording, but so general a 

 statement must be interpreted by the spirit and context, rather than 

 solely by the letter. 



For it is not pretended that uncivilised folk can so discriminate 

 between the subtle gradations of colour as to have words for every 

 shade, but it is none the less certain that where terms are invented 

 for colours, the concrete precedes the abstract. 



Mr. Titchener's question gives me the desired occasion to call 

 attention to my friend Mr. Grant Allen's delightful book on the 

 "Colour Sense" (Triibner & Co.), and especially to the last 

 chapter " On the Growth of the Colour- Vocabulary," from which 

 the following is quoted : — 



" The earliest names must be names of things, or of visible and 



