Jan-. 27, 1SS2.] 



KNOWLEDGE ♦ 



281 



to insert boih. Probably it was among some which were lost ont 

 of a larg-e envelope which burst open dnrinjr postal transit. — M. H. C, 

 Fred Rollet, E. Luxmoke, il. B. E., and others. Thanks about the 

 /.oetrope corrections. We propose to discuss shortly the principles of 

 magic wheels, A-c.— Ues.\. Query on Logic should bo sent to a paper 

 dealing specially with such subjects ; the others inserted. — A. E. S. 

 Daylight sseiH.f only to change unequally in the morning and evening. 

 If we took true solar noon instead of mean noon, the increase would 

 be found uniform. — Conti.nextai. Sh.\i>e. Depends on the eyesight, 

 and no one has yet determined the average eye power for discerning 

 shades.— G. W. Nii-EX. How very carefully you make your articles 

 too long for any use. A coltunn of arithmetical curiosities would 

 be pleasant enough, but four pages wotild be too much. — W. Gibson. 

 Letter on sun heat crowded out.— A. J. M.^ktin. It is absolutely 

 necessary that all ''copy" should be in the printers' hands by first 

 post on Monday. The greater part should reach them on Friday. 

 We are far from being able to promise that letters or tiueries 

 received before Saturday will appear in the next number. To say the 

 truth the correspondence has gio^vn so as to interfere most unduly 

 w it h the conduct of the paper general ly. If our paper were high-priced 

 enough to command the serWces of six sub-editors (besides chess, 

 whist, and mathematical editors) , wit h a sixteen-page correspondence 

 supplement weekly, we might give due attention to the progress of the 

 more important depaitments. But it is not. The worst of it is 

 that so many correspondents send ns really valuable matter, that we 

 must go through the multitudinous heap of matter not valuable, 

 received weekly. Jl everyone who proposes to >vrite to us were to 

 ask first whether he really has something which he ought to say, 

 or whether a question he is going to ask might not quite 

 readily bo ansivered if he took a little trouble for himself, if, 

 then, having decided to write, he would put his communication 

 in the fewest words, and aftenvards strike ont all the extraneous 

 matter which the inexperienced pen will throw in, it would save 

 us a world of really trying labour. Even then, judging from what 

 reaches us, two out of three communications might well have 

 reached the writer's waste-paper basket as ours. Kindly read 

 ag-ain what F.R.A.S., says about wiping the object-glass of your 

 telescope. — H. T. Edmoxds.W. B. Rfs.sELi:., Ac. Every ono who has 

 studied natural history at all knows that the distinctions you 

 mention exist between the Batrachians and the animals now classed 

 as the only Reptiles. The question how they are classified is one 

 thing, the question why they are so classified is another. Te my- 

 self, all such (juestions seem to me not only unimportant, but often 

 mischievous — the student is led to think more of form and phrase 

 than of substance ; he is content to learn the long names which 

 have been adopted in classification, and to attend yery little to the 

 observed facts of nature. One may begin to suspect a man's 

 leal for science (as well as his common sense) when he is 

 anxious to display his familiarity with scientific terminology. — 

 Woori. Many thanks for rectangles, A-c. We had taken yotir first 

 letter as only private in regard to name. — Only a Woman. The 

 toad diJEculties tolerably obvious. As to the other question, the 

 upper weight would be brought to the ground by the effect of the 

 impulse communicated to it. There being no friction, and the 

 weights being equally balanced, there is nothing to destroy the 

 momentum once imparted nntil the weight reaches the ground. 

 The worm actually causes the anar'mic condition, being a blood- 

 sucker. — Ubsa Major. Would you kindly put your questions into 

 compact query form? One is suitable for the Mathematical Column, 

 . the other for the general queries. — J. O. M. So many magic square 

 communications have reached us that " we know not what to do " 

 with them. Each requires careful study, and would occupy a large 

 amount of space ; they interest but a small proportion of our 

 readers. We must now cease to deal with them. — A. Howard. 

 No space at present. — J. F. Russell. See answer above 

 about Electro-Magnetic Theory of Light. — 0. Dawson. We 

 must not perplex correspondents by being too particular. — 

 C. G. R. The plan has been thought of ; but the trouble 

 is that opportunities for observing are so few, and all the 

 part proprietors of an amateur observatory would want to use it 

 when observing conditions were favourable. — A. T. E. No reply to 

 query 49, page 101, has been received. After all, a i|uarter of a 

 man's weight (say he weighed 160 lb.) is not much to lift, and the 

 conditions are of course more favourable after a long breath has 

 been drawn, as you find in lifting a dead weight. This, and a 

 lively imagination, will explain the phenomenon, I think. — I. G. O. 

 No longer space for a question not very important in itself. — Ax 

 Octogenarian. Mercury can readily be seen with the naked eye 

 at the time when the " Nautical Almanac " speaks of him as at his 

 greatest elongation, east or west, — before sunrise when the eleva- 

 tion is west, after sunset when it is east, and of course 

 near the sun's place below the horizon. — Accipent. The cor- 

 rection already made. — C. E. H. Your solution correct and neat. — 

 J. RiCK.iRB. Cat story too long for its purport. (Cat troubled 



with her milk brought a peace offering — fruitlessly — to a before- 

 hated kitten for relief.)— R. W. J. Dog story, ditto ; the 

 '• fore and aft chaff " between yourself and friend about the 

 bulldog has no scientific bearing. (Bulldog, having passed two 

 men on his way to a gate, which he found locked, went 

 back after them, and persistently bullied them till they opened 

 it.) — Chevalier. Game sent to Mephisto. — A. T. C. Seriously, 

 do you want me to say it was a miracle? A distant flight 

 of birds crossing the sun's disc, so that you could have 

 seen them in transit from the nail-holes, but not from the 

 opening just above, would account for what you saw. Or, some 

 other light intercepting passing object, at a suitable distance. If 

 you had looked at once through one of the holes you would doubt- 

 less have seen it ; looking otherwise you would probably have missed 

 it. All I know (not having been there) is that no miracle probably 

 occurred, and that therefore as a shadow was thrown there was 

 something which threw it. Your solutions of the three-square 

 problem are neat. It would surprise you very much, I take it, to 

 hear that the number of solutions is infinifc, " if you may cut them 

 as you will." — Simplex. Not knowing BeU's shorthand system, 

 cannot say ; can you describe it briefly ? — A. Thanks about 

 trotting horse ; regret that your question about Induction 

 Coils has remained unanswered. — W. Wilson. It seems to me 

 the ordinary expres.sion " I see the light" is the one which needs 

 correction. Define light, and put the words " I see " before 

 your definition, and see what comes of it. — F. Halle. Scarcely in 

 our line. — M.A., F.S.A. Is there a mathematical demonstration 

 of the divisibility of matter ? — F. L. C, or Z. L. C, or F. C. S., or 

 F. C. L. About sunlight on fire and poker across it in our article 

 on " Fallacies." — C. R. T. Seeing DebiUissima with a 3i inch O.G. 

 would, in my opinion, mean good eyesight. It is impossible to 

 infer the qualities of a telescope from such obsenations. Mr. 

 Sadler counts about a hundred mistakes in the new edition of 

 Smyth's Bedford Catalogue. You do not saj what sort of cata- 

 logue you mean. — T. R. CL.^pn.iM. Thanks. — Subscriber. Your 

 query indistinct. Besides, to " give you all that is known on the 

 subject," would be to give you two or three numbers to yourself. — 

 A. 'r. Wright. Cannot enter into discussion of various shorthand 

 systems ; they are not scientific matters.— J. H. Garfit. Your 

 article on the giraffe reminds us of his neck; obliged to decline it. 



[Here, for the present, we stop. We beg to invite correspondents' 

 attention to the fact that we have been able to go through only 

 about two-thirds of the correspondence which reached us up to 

 Saturday afternoon (Jan. 21), that only about half of those letters, 

 queries, and repUes which we .should have liked to use can find a 

 place in our columns, and perhaps only about half of that can 

 appear next week. Original matter, notices of books, and paragraphs 

 suited to our columns may make way in some degree, but they must 

 not make way altogether,;for correspondence, queries, and replies, for 

 matter in fine, which we insert to oblige correspondents. — Ed.] 



^otcd on 3rt anil ^tienrr. 



" Cold Catchi.vg." — It is noteworthy as a curious yet easily ex- 

 plicable fact, that few persons take cold who are not either self- 

 consciously careful, or fearful of the consequences of exposvire. If 

 the attention be wholly diverted from the existance of danger, by 

 some supreme concentration of thought, as, for example, when 

 escaping from a house on fire or plunging into cold water to save 

 life — the effects of '■ chill ' are seldom experienced. This alone 

 should sen-e to suggest that the influence exerted by cold falls on 

 the nervous system. The immediate effects of a displacement of 

 blood from the surface, and its determination to the internal 

 organs, are not, as was once supposed, sufficient to produce the sort 

 of congestion that issues in inflammation. If it were so, an inflam- 

 matory condition would be the common characteristic of our bodily 

 state. When the vascular system is healthy, and that part of the 

 nervous apparatus by which the calibre of the vessels is controlled 

 performs its proper functions normally, any disturbance of equi- 

 librium in the circulatory system which may have been produced 

 by external cold will be quickly adjusted. It is, therefore, on the 

 state of the nervous system that everything depends, and it is, as 

 we have said, on the nervous system the stress of a ''chill" falls. 

 Consciousness is one element in the production of a cold, and when 

 that is wanting the phenomenon is not very likely to ensue. 

 It is in this way that persons who do not cultivate the fear of cold- 

 catching are not, as a rule, subject to this infliction. This is one 

 reason whv the habit of wrapping-up tends to create a morbid 

 sensibility. The mind by its fear-begetting precautions keeps the 

 nervous system on the alert for impressions of cold, and the centres 

 are, so to say, panic-stricken when only a slight sensation occurs. 



