122 



KNOWLEDGE . 



[Aug. 8, 1884. 



A TEST has been made of balancing a straightedge three feet long 

 and weighing thirteen pounds on a human hair. It was placed on 

 another straightedge, and the hair introduced between the two 

 faces near the centre. The upper one was moved on the hair as a 

 roller until the ]>roper point was reached, when it remained 

 balanced perfectly, so that light could be plainly seen the entire 

 length of the straightedge between the two surfaces, except where 

 the hair separated them at the middle of their length. — Sciejilific 

 American. 



Feom the annual report of the Metropolitan Board of Works for 

 1883 it appears that the staff of the London Fire Brigade consists 

 of 670 men. The number of firemen employed on the several 

 watches kept up throughout the metropolis is at present 108 by 

 day, and 253 by night, making a total of 361 in every 24 hours ; 

 the remaining men are available for general work at fires. The 

 number of calls for fires, or supposed fires, received during the 

 year was 2,630. Of these 337 were false alarms, 149 proved to be 

 only chimney alarms, and 2,144 were calls for lircs, of which 184 

 resulted in serious damage, and 1,96U in slight damage. The fires 

 of 1883, compared with those of 1882, show an increase of 218; 

 and, compared with the average of the last ten years, an increase 

 of 446. 



Use of Disinfectants in Paris. — Experiments in the disinfecting 

 of rooms have been carried on in a Paris hospital, and many have 

 witnessed the experiments conducted by Drs. Pasteur and Dujardin- 

 Beanmetz. At present two systems are under discussion — the use 

 of the liquid sulphurous anhydride and the simple burning of sul- 

 phur. At first the sulphur would not bum, and the acid, though it 

 told on the litmus test-papers, did not kill the microbes which 

 M. Pasteur had left in the room. Now, however, by pouring a 

 little alcohol over the sulphur, it has been made to burn very 

 successfully, and by using a larger quantity of the disinfectant, 

 whether in a liquid or a solid state, the microbes were killed. 

 Both the rooms measured 98 cubic metres, and 2 kilos, of snlphur 

 had to be burnt before the living organisms left in the room were 

 destroyed. This is about the same amount which long experience 

 in England has proved to be necessary. 



" Let Knowledge grow from more to more." — Alfbed Tennyson. 



Only a small proportion of Letters received can possibly he in* 

 serted. Correspondents mvst not le offended, there/ore, should their 

 letters not appear. 



All Editorial communications should he addressed to the Editor of 

 Knowledge; all Business communications to t?ie Publishers, at the 

 Office, 74, Oreat Queen-street, W.C. If this is not attended to 



DELAYS arise FOR WHICH THE EDITOR IS NOT RESPONSIBLE. 



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

 payable to Messes. Wyman & Sons. 



The Editor is not responsible for the opinions of correspondents. 



No COMMUNICATIONS ARE ANSWERED BY POST, EYSN TBOUGB BTAHFU) 



AND DIRECTED ENVELOPE BE ENCLOSED. 



VENUS IN A THKEE-INCH TELESCOPE. 



[1356] — I should like to ask readers of mj- paper on p. 92, to 

 float a pale wash of Indian ink over the inner (the upright or right- 

 hand) edge of Venus as shown in the woodcut (Fig. 1.) on that 

 page, so as to cause it to melt, as it were, into the surrounding sky. 

 The engraver has removed the shading from it, and erroneously 

 left it too sharp and bright. 



A Fellow of the Koyal Astronomical Society. 



MIND AND BK.UN. 



, [1357] — Your very fair critique on Biichner's " Force and 

 Matter" contains one remark on which you ■will, perhaps, permit 

 me to say a word — viz., that it is inconceivable " that thought, &c., 

 i^' motion in matter." To me this seems to follow clearly ; for if 

 it is proved that no motion of brain-matter, no thought, is a truth — 

 and Haeckel, Hurohke, Vogt, and other eminent scientists clearly 

 say BO — it appears to me very conceivable and reasonable to say 

 that thought is a mode of motion of the molecules of the brain. 

 The more perfect the brain the more complicated these move- 



ments, the deeper the thoughts, seems to follow as a matter of 

 logic. 



From the simple movements of attraction and repulsion, the 

 loves and hates of matter, it is conceivable to me to trace the 

 gradual development of thought movements pari x-assu with the 

 physical development of the human brain in course of evolution 

 through immense periods. F. W. H. 



[I may be as obtuse as F.W. H. appears to consider that the 

 Reviewer of Biichner's work is, but I confess that I fail to see that 

 because (as is indubitable) no thought occurs — or can occur — without 

 motion of brain matter — ergo — such motion is itself thought. No 

 tune was, or conceivably ever could be, 'played upon an organ without 

 the movement of the keys, bellows, &c., but it would appear an 

 old mode of reasoning to predicate that such movement was the 

 tune itself. — Ed.] 



FLORAL PARASITISM. 



[1358] — During the past spring I have had a fine specimen of 

 Cjrobanche minor make its appearance in a flower-pot containing a 

 double pink geranium, and placed at a window in a sitting-room. 



When It had finished flowering I examined the root. It had 

 firmly engrafted itself on the root of its host, which had made but 

 little growth, and no recent roots at all. 



Is it not unusual for orolanche to establish itself on such a plant 

 as a geranium? Wm. H. Allen. 



[The orobanchacecB are all parasitical on the roots of plants ; bat 

 they mostly attach themselves to wild ones. Yours does seem 

 rather a singular instance. — Ed] 



LETTERS RECEIVED AND SHORT ANSWERS. 



Nigel Doble. — A 4-in. object-glass of 66 in. focus ought to suit 

 your purpose. You understand, of course, that for the eye-pieces 

 of which I gave the details on page 79 to give the magnifying 

 powers set against them, it is imperative that they should be em- 

 ployed with an objective of that focal length. Any alteration in 

 that respect would involve a corresponding alteration in their 

 respective powers of amplification. I neither can nor will recom- 

 mend tradesmen. The firm you mention onl}' sell — they do not 

 make— object-glasses. — A. Roberts. See what you can do with X 

 Ophiuchi. This is a very severe test for an instrument of the size 

 of yours, r in the same constellation is, I am afraid, just beyond 

 your instrumental capabilities. Try too the double- double star t'" 

 and i- Lyrge, and see how many stars you can make out between 

 the two pairs. — G. H. Robertson inquires what is the chemical 

 composition of the substance called *' Essence d'Orient " used in the 

 manufacture of artificial pearls. Can any of our readers inform 

 him ? I suppose he does not mean the powdered bleak or minnow 

 scales with which glass beads are internally coated to imitate 

 pearls? — Anonymous (Bradford). Thanks for the cutting from 

 Le Temps containing M. Cotteau's essay on the Krakatoa eruption. 

 It tells in the picturesque French fashion what has appeared in 

 print in other forms over and over again. — John Branch sends 

 me a letter from "Enquirer" with reference to Spiritualism, 

 which is very much too long for insertion. Some years since, 

 impressed to a certain extent by the blatant assertions of so-called 

 " Spiritualists," I investigated the question thoroughly for my own 

 satisfaction; and am hence in a position to reply to, at all events, 

 some of "Enquirer's" queries. Imprimis, neither furniture nor 

 anything else ever moves unless it is pushed or lifted by human 

 agency. In the next place, the whole of the race of mediums (save 

 a very small percentage, indeed, who are insane) are arrant rascals j 

 who, as I have said before in these columns, ought, one and all, to 

 be prosecuted under 5 Geo. IV., c. 83, s. 4. And lastly, do not let 

 " Enquirer " delude himself with the belief that he will be suffered 

 to conduct any experiments in a scientific (to say nothing of a 

 common-sense) fashion. If the "Spiritualists" forming the 

 " circle," find out that he is sceptical, and likely to detect the vile 

 cheat who trades upon the holiest feelings of our nature by pre- 

 tending to communicate with our loved dead ones, he is told that 

 "his influences are antagonistic," and that he must shift his place 

 in the circle, &c., and so he is wedged in between people who take 

 exceedingly good care that he is in no position to lay hold of the 

 medium himself, that medium's paper tube, or anything else 

 that may be "floating" about in the dark. I declare that I 

 have sat in a sort of dumb wonder at the fatuous and 

 idiotic manner in which believers have gone two-thirds 

 of the way to meet the imposture of the medium, when 

 I have been present at a seance, the indifferently-performed 

 conjuring tricks of such mediums having been received by these 

 nobe-mouches as the veritable acts of beings from another sphere ! 

 I have said before, though, and must here repeat, that I cannot 



