426 



KNOWLEDGE. 



November, 1911. 



Irequently happens that a darU-ground ilkiiiiinator. i.e.. a 

 condenser primarily devised for ordinary microscopic observa- 

 tion in a darU field, is available for ultra-microscopic observation : 

 indeed, in many cases both kinds of observation are made con- 

 currently. The examination of a preparation of saliva 

 furnishes an instance of this. With our concentric condenser 

 (after Dr. Jentzsch of our Scientific Department) one can see 

 in this medium a few organisms moving across the field in 

 snake-like fashion, and others of a rod-like shape, whilst in 

 addition to these there are to be seen bright discs surrounded 

 by one or several bright rings and e.xecuting quivering move- 

 ments. The latter come into view by an ultra-microscopic 

 process, whilst the others are seen under simple dark-ground 

 illumination, though sometimes their trans\erse dimensions 

 are of the ultra-microscopic order. 



It is to be hoped that in future, makers as well as users of 

 these optical instruments will endeavour to prevent a contin- 

 uance of the misunderstanding at present existing, by employing 

 the correct term, especially when referring to dark-ground 

 illuniinatiun of micro-organisms. ]•'. Ll-IT/. 



TH1-: NKW .ASTRUNUMV. 

 Tu the Edtturs uf " Knowledge." 



Sliss. — I was delighted to see your able statement of the 

 facts confirming Professor Bickerton's theory in your August 

 issue, and still further pleased to read his remarkable articles, 

 on the story of Nova Persei, and on double and wonder stars. 



I ha\'e always lo\-ed astronom\', and for thirt>' \ears I ha\e 

 been a Fellow of the Royal Astronomical Societx', and during 

 all that time nothing has interested me so uuicli as this 

 beautiful theory of the third body. 



At Professor Bickerton's lecture at the Roval Colonial 

 Institute. I heard Mr. Knobel. who has lieen twice President 

 of the Royal Astronomical Society, express his opinion so 

 strongly. that I was delighted. He said: " It has been an extreme 

 pleasure to me to listen to Professor Bickerton's eloquent 

 address. I have given some attention to astronomy mxself. 

 and I can saw that the basis of Professor Bickerton's theory 

 is such, that it nmst command, not only the attention and 

 consideration, but I tliiiik. the assent of the niajoril>- of 

 astronomers." 



Since this lecture as I have gradually realized how iar- 

 reaching is the scope of the principle of the third body, w ith 

 its power to capture, its explosive energy, and its capacity to 

 sort its atoms, I have come to believe that this generalization 

 marks an epoch in astronomy. I heard Professor Bickerton 

 debate the subject, at the British Astronomical Association, 

 and was struck with the ease with which he confuted the 

 objections of able astronomers. Hence I felt assured that 

 the theory had come to stay, and subsequently his letters in 

 TIic Times confirmed this impression. I have read and re- 

 read his book, " The Birth of Worlds and Systems " published 

 in ■■ Harper's Library of Living Thought." Its study convinces 

 me that the theory of Professor Bickerton's, is the only one 

 that corresponds with the facts of observational astronomy. 

 With regard to novae, the question so ably discussed in the 

 September number of " Knowledge," I have personally 

 compared the light-curve, and series of spectrograms of Nova 

 Persei, with the complex deductions made from the dynamical 

 study of the third body, and they fit perfectly. I believe that 

 the Southern .Astronomers are right when they say that. " had 

 the idea been used from its inception, merely as a working 

 hypothesis to guide celestial observations, astronomy would 

 have been years ago where it is now." The Government of 

 New Zealand has shown its deep interest in basic science, 

 and deserves the gratitude of the learned societies, in sending 

 Professor Bickerton to explain his New Astronomy to the 

 scientific world. J. McCARTin'. I'.'r.A.S. 



TO FIND .\P1'R( JXIM.NTI'.L'i SIDICKF.VL TIiMIC. 



Tu the Hditors uf " Kxowli:dge." 

 Si us. — The state of the sky at a particular hour may be 

 approximately ascertained by the use of the simple equation 



*Note. — Line I - Setles is t'assiupeia's Cliair ; line 5 — .^rgo rises 



Tanantis is 



l\.A. = h-h2m -(-.T. where h is the hour counting from 

 midnight, and m the number of the month. 



This will gi\e the R.A. of the zenith, or Sidereal Time on 

 the 7th of the month, within a few minutes. By the daily 

 allowance of four uiinutes the R.A. on any other day of the 

 month may be determined. Thus, on the 22nd of the month 

 the R..\. w'ill -^h + 2m + 6. 



N.B. — For greater accuracy in January and February the 

 dates should be the 6th and 21st, and in March, May and July 

 the .Sth and 23rd. 



E.xaiuple: .\t noon on November 2'Hh, st-ven days after 

 tile 22nd; R.A. - 12 + 22 + f->h. 2.Sm.^XVI.2.s'. The correct 

 time, as shown b\' W'liitaker's Aliiuiiuiek is X\'1.20' 1". 



.\g.iiu. if the 1\..\. of .1 particular st.ir or constellation is 

 known, its pci,.,ition in the sky at an>- dale .md hour may be 

 calculated. 



Example: The R..\. of Siriu.-. is \'I.4r. To find the time 

 cif its southing on 15th March, seven d.ivs after the 8th. 



R..\.- VI.41 -h-f 64-5h. 2.Sm. 



.'. h — — 5h. 47m., which signifies ,t hours 47 minutes 

 befcire 24 o'clock or midnight; which will be XIX. 1,1 o'clock, 

 or 7.1 .! p.UL 



.\gaiii, to find the date on which a given meridian will be 

 south .it ;i partli nl.u' hour. 



Example: When will Alt.iir. R.A. XIX. 4(.. be south at 

 O.JO p.ni.:- 



R.A. = XIX.4(i-21h. .i()m. + 2ui4-rih. Kini. 



(The last figure nmst be chosen, so that the \.ilue of 2in will 

 be e\en.l 



.'. 2m-XIX.4(.-XXVII.46= -.S,= +l(i, .'. m = 8. 



The dati' will be .August 26th, four days after the 22nd. By 

 Whit.d;cr. R..\. at noon on .August 26th is X.14; at 0.30 p.m. 

 it is XIX.44. 



In the .ib.sen(e of a Star .Atlas or Map. the following lines 

 ui.iy be useful: — 



Mi;m()KL\ Techmca' 

 shineiii:; the pnsilioii of the prineipal stiir.s in tJie sky. 



Sides. .Andromeda, et PISCFS, et Cetus, .Achernar. 



Perseus. Plei:idesi|ue, .ARIES, Mira, Eridauusque, 



.\in'iga, Orion, T.AURUSque, Lepusque, Columba. 



lum GEMINI, Procyon, et Sirius, atipie Canopus. 



CANCER, et Hydra, .Argo, cui puppim \ela seqiumtur. 



Indicat Ursa Polum coeli, tergunique LEON IS. 



Cauda, Canes, VIRGO, Corvus. Crux, et Centaurus. 



Lrsa. Draco, .Arcturusque, Corona, et LIBR.A. Lupusque. 



litanin, Heracles. Ophiuchus. SC( )RITO, et Ara. 



A'ega. Caput Cygui. Volucerque Tonantis. et ARC US. 



Cepheus, et Cygnus, Pavo, C.APRICCJRNUS, et Indus. 



Pegasus, .Australis qnoque Piscis, AOU.ARIUS, et Grus. 

 These lines, taken in order, give the constellations found in 

 the segments of the sky contained between the R..A. meridians 

 XX1\' and 11, 11 and \\'. ]\' :ind \'I. and so on. 



i'ri:d p. tawa )R. 

 Tin; I'UKKiNji: imii;nomi;non. 



To the Editors of " Knowledge." 

 Sirs, — It is a matter of conunon observation that coloured 

 objects change their aspect in a remarkable manner just after 

 sunset. If, for instance, when twilight has set in, we look 

 about us in a garden containing flowers of various hues, or in 

 a library full of nruiy coloured books, we soon become aware 

 of a striking change which has taken place in the relative 

 brightness of the tints surrounding us. We notice that the 

 blues are much lighter, and the reds nmch darker than when 

 they are seen in ordinary daylight. So marked is this 

 phenomenon at times, that certain blue tints appear almost 

 white, while red tints, on the other hand, become so dark that 

 they might be mistaken for black, if, indeed, they do not 

 entirely pass unnoticed. The cause of this well-known effect, 

 which bears the name of the Bohemian physiologist Purkinje 

 (17S7-1S69), who first described it, generally receives its 

 explanation in the peculiar differential colour sensitiveness of 

 the eve, which loses sight of a red sooner than a green ray. 



stern first ; line 7 — Cauda is the Bear's Tail : line 10 

 .\(juila. 



A'lilucer 



