Jan. 6, 1882.] 



KNOWLEDGE • 



213 



either. — Zabes. When did we promise to insert authentic abnormal 

 mental phenomena ? We promised to insert accounts of scientific 

 experiments relatinjr to mental matters. Tlie story yon relate, 

 "told you by a reliable person," can hardly be so described. It 

 is, in fact, one of those which we considered likely to reach us 

 too freely if wc opened the columns of Knowledge to accounts 

 of spiritual manifestations. — H. Woolley. Wo are inclined to 

 agree with tou, perhaps because it would save us much trouble 

 to exclude "such letters as you refer to. — Amos Hinton. Because 

 fresh cold air continually replaces that which had been in contact 

 with the body, which in a calm would be warmed. — A 

 CE0SSI.EY. The nebular hyjjothesis of Laplace is seldom correctly 

 explained. An intcrcstinsf account of it is given in Nichol's 

 "Architecture of the Heavens." — G. H. Mapleton. Printing the 

 star-maps on a separate loose sheet involves extra expense, and 

 this is a rather important consideration in a journal so cheap as 

 ours. — A. T. C. Absolutely impossible to find room for your 

 solar puzzle. But it is certain that if you had got up while the 

 phenomena were in progress, and looked tlirough the holes, 

 at the sun, you would have seen some object, near or far 

 off, obscuring his disc. — Osw.\ld D.^wsox. You require our 

 correspondents to be somewhat too precise. They know what they 

 mean, pretty well, when they speak of the relative position of the 

 sexes (to take one of your examples) ; why insist that they should 

 define when, where, and how, in precise detail, thej- mean the 

 sexes to be compared. — A correspondent, who gives us no name, 

 asks us to explain the electro-magnetic theory of light. We know 

 of no such theory. The writer who says the undulatory theorj' is 

 fast being swallowed up piecemeal by the electro-magnetic 

 knows very little about the matter. The evidence for the undu- 

 latory theory is simply overwhelming. — W. E. Blythe. Thanks 

 for abstracts, which shall appear. — Fred. Denier, Milwaukee. 

 Thanks for encouraging words. — Harri.s J. J. Brum, and J. P. 

 GiLMoUR. Thanks ; one sees the silver side, the other the 

 golden : but it is the same shield. — J. Calvert. Your advice 

 to the emiHcnt professor, coupled with that which you are good 

 enough to give us, brings to the mind, somehow, the instructive 

 lines ; — 



Teach not a parent's parent to extract 



The embryo juices of an egg by suction ; 

 The good old lady can the feat enact 



Quite irrespective of your kind instruction. 

 A. J. Maas notes that he receives Knowledge regularly every 

 Sunday in Switzerland, so that booksellers who supply it in 

 England on Tuesday or Wednesday might presumably do better. 

 — Edwin Wooton. Fear we cannot in any way advance youi- 

 scheme. Personally we are not in love with the society system 

 of science work. Most scientific societies seem, somehow, to act 

 as nurseries of disputes and diflScnlties. — Raven. Whether the 

 account you refer to is reconcilable or not mth the theorj- of 

 evolution is a question not open for discussion in these columns. 

 The account, whether right or wrong, is extra-scientific. — F. S. C. 

 Your original polygon was an octagon. The polygon which your 

 later communication requires could be readily drawn if any angle 

 could be trisected, othcnvise not. Consider the trouble taken by 

 Euclid in Book IV. to show how polygons whose sides subtend 

 particular angles may be described, and yon will see that we 

 cannot give as part of a solution such a direction as this -. " The 

 apex of angle being at centre of circle, inscribe a polygon which 

 shall have three of its sides between sides of angle, commencing 

 the polygon at one of the sides," wnthout showing first how this 

 is to be done. Your other communications thankfully received. — 

 H. C. (i.) The accepted theory of light is that it arises from an 

 undulatory motion in an ethereal medium occupying all space. 

 (ii.) Cold water is heavier than warm, (iii.) We have heard of 

 no new theory respecting the formation of the coal-measures. 

 (iv.) I.H.S. stands for Jesus hominum salvator. — Philadelphvs. 

 The writer of the article in question in no sense infringed our 

 rule. He puts it as a scientific view that faith in di-eams as 

 supernatural visitations is one among many survivals of rude 

 primitive philosophies. He indicates also pretty clearly his own 

 telief that the phenomena of dreams are all readily interpre- 

 table without any appeal to the supernatural. This is unques- 

 tionably the attitude of science in the matter. I, at any rate, 

 should be very much surprised to hear that any man of science 

 \iewed the matter differently. Well, now, you quote certain 

 statements which do not seem reconcilable with these views. 

 But science has nothing whatever t6 do with those state- 

 ments. They are entirely extra-scientific. You might as well 

 ([uotc other statements, found in company with those you 

 mention, to show that an account here of scientific views respect- 

 ing floatation must be regarded as a breach of our rule that 

 dogmatic religion should not be attacked in these columns. Or a 

 Brahmin might as reassonably object to the views about distracted 



attention under head, " Mind Troubles," that they seem to him 

 inconsistent with correct views about the Xirvana. Can you not 

 see that the supernatural has no i)lace in arguments relating to 

 the natural ? .\s to the inconsistency you indicate, we may or 

 may not, Mr. Clodd might or might not, agree with you. What 

 can it matter one way or another, when we positively decline to 

 have such questions discussed hero ? In reply to your other ques- 

 tion, Whitaker's Almanack decidedly overrates the prolificness 

 of Bradford folk. It should be not 83-1 but 3S1 per thousanil.— 

 F. St.\nley. Newton's estimate of terrestrial compression was 

 based on an incorrect hypothesis as to density at different levels 

 below the surface. Joyce is not an authority, any way. The 

 true compression is about l-300th, or polar radius about 13i 

 miles less than equatorial. — A. J. Makti.v. Rightly understood, 

 what we said was an answer to your question. The focal image 

 of a planet is examined by the eye-piece (which is really a micro- 

 scope), and cannot be examined with an eye-piece of more than a 

 certain power, because its imperfections are such — no matter 

 how excellent the object-glass — as to preclude more than a cer- 

 tain degree of magnifj-ing. By receiving the image on a screen, 

 eveu were the screen perfect, we do not diminish its imperfections, 

 and we lose light. Therefore, wo cannot use a microscope in the 

 ordinary way with any advantage. In fact, if an eye-piece is 

 used to throw the rays on the screen, the image so formed can 

 be best uiagnified by simply increasing the screen's distance from 

 the eye-piece. We are then magnifying without any of the 

 optical disadvantages which would result from using a micro- 

 scope. But we find no increase of distinctness in this way after 

 a certain convenient distance has been reached — only loss of 

 light and such increase of all imperi'ections that the image 

 becomes confused and indistinct. — Paugol. Thanks; but at 

 present no space. — Excelsior. If you only knew how much 

 labour we should save by doing what you ask ! But then many 

 would say it was pure selfishness. 



^otx6 on Srt anU ^nrnre. 



A New Variety of Glass. — A Vienna chemist has recently 

 discovered a new variety of glass. It does not contain any sUica, 

 boric acid, potash, soda, lime, or lead, and is likely to attract the 

 attention of all professional persons on account of its pecuUar 

 composition. Externally it is exactly similar to glass, but its lustre 

 is higher and it has a greater refraction, of equal hardness, per- 

 fectly white, clear, transparent, can be ground and polished, com- 

 pletely insoluble in water, neutral, and it is only attacked by 

 hydrochloric or nitric acid, and is not affected by hydrofluoric acid. 

 It is easily fusible in the flame of a candle, and can be made of any 

 colour. Its most important property is that it can be readily fused 

 on to zinc, brass, and iron. Is can also be used for the glazing of 

 articles of glass and porcelain. As hydrofluoric acid has no effect 

 on the new glass, it is likely to find emplojinent for many technical 

 purposes. — Wiener Oevjcrbe Zeitung. 



An Electric Buoy'. — A daily contemporary states that experi- 

 ments are being made in the Lower Bay, New York, with a new 

 electric buoy, the invention of Mr. Bigler, of Newbnrg. Mr. Bigier, 

 it appears, owns the patent of the old Courtney Whi.'stle Buoy, the 

 principle of which he combines with an intermittent light, the same 

 power which blows the whistle being used to generate the electricity 

 that furnishes the light. The rise and fall of the waves compresses 

 the air inside the buoy. When this pressure has reached a certain 

 point, it works a dynamo machine and burner furnished by the 

 Edison Electric Light Company. This machine is supposed to gene- 

 rate enough electricity to show an intermittent light. When the 

 pressure ie exhausted by the action of the machine, which makes 

 about 300 revolutions per minute, the light goes out until the pres- 

 sure is renewed by the motion of the waves. The more violent the 

 waves the more powerful the light, nji to a certain point. Thus the 

 light is at its brightest during a hurricane. — Scientific American. 



The Winter Flight of the Swallows. — The swallow is one of 

 the best known, and, therefore, most interesting, of migratory 

 birds. Excepting when kept in confinement, this bird knows 

 neither the extreme of hot nor cold weather. As soon as the cold 

 weather approaches, he migrates with his family to a warmer 

 climate, and again to the northward when the temperature of its 

 second home becomes inconvenient to its sensitive existence. In 

 England, as a general fact, the swallow does not arrive until the 

 second week in April, and takes his departure about the middle of 

 September. Before the time of their flight, they assemble in vast 

 numbers in a comfortable locality, and are seen chattering very 

 eagerly, as if holding a huge convention for the settlement of affairs 

 before starting on their long journey. Although starting off 



