March 24, 1882.] 



♦ KNOWLEDGE ♦ 



459 



Slnsilurrsf to Corrrsponlifnts. 



• • All eommuntcatiotu for the Editor requirinff eartjf iitteHtion tkould reach the 

 OMee on or be/ore the Saturdat/ preceding the current ieeue of Kxowlrdob, the 

 itereeeing circulation o/ ichich compels u* to go to prete eartg in the tceeh. 



HlIfTS TO CoBBBSPOXDBSTS. — 1. -Vo qneftione aiking for ecieiitijic information 

 can be anevered through the pout, '^. Letters tent to the Editor for eorreepondente 

 cannot be forvarded ; nor etin the namee or addrestee qf eorreepondente be gicen in 

 -4 . Jitmer to pricate inquiriee. 3. -Vo queries or replies savouring qf the nature qf 

 advertisements can be inserted. 4. Leltirs, queries, and replies are inserted, unless 

 conirani to Rule 3, free of charge. 5. Correspondents should lerite on one side 

 i tnlf of the paper, atut put drawings on a separate leqf. 6. Each Utter, query, 

 rtflf should have a title, and in replying to letters or queries, rife ^- >-> 



should be 

 o» J* to the number qf letter or querg, the page on which 'it appears, and its title. 



' W. S. Jackson, C. R., and others. Seventeen rorrespnn- 

 deiits already have " raved " against masric squares. We therefore 

 I must not insert anything more about them foragood while. Mr. Miles, 

 ' however, will willingly, I doubt not, say where Poignard's method 

 lirst appeared. — Three Chroxos. Surely you are the ones to 

 'answer what you call the ■'mm watch query." — T.\k.\x.\ki. The 

 I horizon sinks as we ri?e above the eai'th's surface ; but the dip is 

 ' vcrv slight, even for a considerable height. The eye cannot detect 

 it readily, even from a height of four or five miles. — A. P. M. Your 

 I letter about weather forecasts is long, but we will try to find space 

 'for it. — E. S. Kennedy. Sayce's writings on Assyrian literature 

 {contain a good deal about the star- worship of the Assyrians. Pub- 

 ilished, I think, by Bagster. — E. Kelly. You will not find that 

 jXewcomb attributes the acceleration of the moon to the tidal 

 |wave. He says that a part of the acceleration is explained by 

 (the effects of the tidal wave in retarding the earth's rotation. — 

 jClemext W. Jewitt. Cannot identify the year when " two comets 

 came in (some time about 1858)." — J. Thkistax calls attention to the 

 ifact that the barometer, after being abnormally high for several 

 (weeks, fell rapidly on February 25th, yet there were no explosions 

 ■ in coal-mines, as predicted by Mr. E. C. Eapier. — Scrit.\tok. Let 

 IP be the length of a perpendicular let fall from one angle of 

 ja tetrahedron to opposite /ace, and let p be the length of perpen- 

 dicular from an angle to opposite side of any face including the 

 angle, and let s be length of a side. Then we know that 



and 



= \A-i4^3; 



-V^'-f= 



Jv/8 = 5v/6 = sv'l 



= 3V--3 



and the centre of the tetrahedron lies on each of the perpendiculars 



p 

 from the angles on opposite faces, at a distance — from eacbface, of 



|v § from any face. 



If s = 16, then this distance 



Wl 



Uaceenzie, M.D. Considering how much it is the doctor's 

 interest to discountenance vaccination, supposing it to be really 

 protective (as every one knows it is), you can hardly expect me to 

 believe that doctors advance statements opposed to the truth in 

 this matter, when they advocate vaccination. An epidemic of 

 Bmall-pox would be a fortune to mercenary medical men, protected 

 themselves by vaccination. The paltry vaccination fees are 



nothing by comparison with the fees they could fairly 

 vtiim in the times before vaccination. If small -pox were 

 rife in any city where yon or I dwelt, should we not at 

 mce be vaccinated, and should we not then feel as safe as if 

 there were no such epidemic ? Frankly, I should consider myself 

 pnblic offender if I admitted one line here in favour of the views 

 laintained by the .Society for the Preservation of Small-pox. As 

 for what yon say about Whist, doubtless many wonld prefer to have 

 the space now allotted to Whist given to some other subject ; all are 

 not Whist players. But the omission of several subjects which all 

 lo not like might readily lead to the omission of Knowledge alto- 

 jetiier. Every onr must not expect Knowledge to be filled with 



those subjects lie may chance to like. I think we give our fair 

 •Wopenny worth of science, without the Whist and the Chess. — 

 toSAN E. Gay. Your letter was sent at once to printers, and will 

 Iftpear soon. — A. H. H. My papers on Differential Calculus would 

 pmbably be simpler than you would need. — Donald King. An 

 kl^le on sun spots would be necessary to answer your question ; 

 nU, probably have one shortly. Meantime, any good book on 



onomy would help you. — H. B. Lindsay. Part of your letter 

 lefeiTed to F.R.A.S. May shortly write about space; but your 



irks need not, therefore, be withheld. You know our require- 

 nents as to space. — J. McDowell. Your name entered on list for 

 •fos. 2, 3, and 5. Yon are quite right about our proposal on p. 302 ; 

 ve were but jesting. — F. Ram. To Darwin and Wallace, of course, 

 s due the credit of the recognition of the accepted theory of 



evolution. Spencer's researches are, however, of great importance. 

 — Carpenter. If you really want to know its weight, put it in the 

 scales; it you set the query as a "sum," perhaps you will explain 

 what you mean by saying " the surface of the wet part was 209--14 

 inches." — Ixcredilots. Probably, table turned by pushing ; 

 depends how it went. — Q. E. D. Hog puzzle right. — W. H. Hewett. 

 The conditions seem equally favourable. — Spencer Byder. I should 

 imagine that you might more readily infer the existence of a God 

 fx'om your own personal sense of his works, than by the rather 

 roundabout way yon suggest. Does the most beautiful painting of 

 a landscape, or the most perfect description of the glories of the 

 heavens, give you so good an idea of the existence of a God as the 

 landscape itself in one case, or the star-lit vault of heaven in the 

 other? — J. A. C. Ollard. Yes; but suppose 20,000 copies of sup- 

 plement were printed, " containing letters only or chiefly," and only 

 1 .000 were sold ; how theni' On the reason of animals question, 

 what yon " believe " and " do not believe," might not interest 

 all our readers. — Finite Space. Neither can I imagine space 

 limited : nor can any one ; nor can any one imagine infinite space. — 

 C. J. TooTELL. Thanks for picture of sun-spots, but by time it 

 would appear they wonld not be there. Your method of focussing, 

 where rackwork is not very delicate, is, I know from experience, 

 excellent. (It is to let the eyepiece te not fully screwed "home," 

 and then adjusting roughly by means of rackwork, to get exact 

 adjustment by turning the eyeglass.) Only it is not safe to have 

 the eyeglass but half screwed in ; for if you have many adjust- 

 ments, and a preponderance chance to be by screwing outwards, 

 the eyeglass may fall out. — G. T. M. Both your suggestions are 

 already under consideration. Thanks. — M. V. M. Thanks ; but too 

 long, and scarcely suitable otherwise. — H. W. We do not want 

 metaphysics, melancholy though you think the future of science is 

 to be without it. — SiRirs. Veiy doubtful at present about that 

 companion. Spectroscopic evidence shows Sirius to be probably in 

 an earlier stage of sun-life than our own sun. — Jawge. Dental 



6 1—1 7—7 



formula : incisors, -pr ; canines, :; — r; molars, = — i = 44, — means 

 ' (j 1 — 1 ( — 7 



that the teeth are arranged in the two jaws, Jawge, thus : — 



MMMMMMMCIIIIIICMMMMMMM 



MMMMMMMCIIIIIICMMMMMMM 



where SI stands for a molar, C for a canine, and I for an incisor 

 tooth. — Thomas Smith, Jun. Describing a man's character from 

 his bumps is not phrenolog}-. Study what Gall and Spurzeim 

 really taught, and yon will see what it is that science rejects. — 

 Ishtah. AUruiiin, derived from alter, "another," means the con- 

 sideration of the interests of others before our own, just as egoism 

 from etjo, I, means the consideration first of our own interests. — - 

 G. T. W. M. There is a small book by Abbott, head-master of 

 St. Paul's School, on the " Queen's English." I forget publisher's 

 name and price. — J. H. Cobbett. You are too exacting. Parallax 

 allows only a top to the earth, and you ruthlessly ask for a model. 

 You might as well ask for soundings of the bottomless pit. — W. B. 

 Thank you for reminding me ; yes, the ratio of circumference of 

 circle to radius is, as you say, fixed ; but in the solution of the rod- 

 tossing problem this constant ratio comes in with a factor which is 

 not constant. — E. L. R. Yes ; ice-pai-ticlescan and do cause parhelia 

 (not perihelia, as the Gazette prints it). — G. A. K. The historical 

 value of the play called Shakespeare's Henry VI. is very small. 

 Shakespeare wrote but a small proportion of it. As you say, 

 the Bear |and Ragged Staff were not taken by the Nevilles 

 before their alliance with the Warwick family to which the crest 

 belongs. — W. Sumner. The rotation of thu earth has been regarded 

 as appreciably uniform. It is not quite so, but the variation is very 

 slight. The question is, however, too complicated to be discussed 

 here. It wants an article to itself. 



i^tttrrsi Jxfrnfarli. 



W. S. Jackson, K. Huskisson, I. H. Vulliamy, R. Tollit, Praxis, 

 K. L. P., J. Murray, Metamorphosis, Pertinax ('Tis true, 'tis pity). 

 Cosmopolitan, Anxious One, W. John Grey, J. U., Jlongredian, 

 Semper Paratus (so i.-5 W. P. B.), Jupiter Tnnans (save ns), M. 

 Purvis, J. Harmens, F. M. Rogers, Pollaky, H. F. C, J. H. 

 Marvin, P. Tindale, M. Morrison, K. P. M., R. Lecky, Circle-sqnarer, 

 Triangular, Queer Querist, M. Rambures, S. S. T., Rev. M. M., 

 Castrensis, Ad ardua tendo (Respice finem), C. Collins, Anti- 

 humbug, Simplex, Verge, H. Jowett, K. Prothero. 



Poxd's Eitbact is a certain core for Rhenmatisin and Oout. 

 Pond's Extract is a certain cure for Hemorrhoids, 



Pond's Extract is a certain cure for Neuralgic pains. 

 Pond's Extract will heal Bums and Wounds. 

 Pond's Extract will cure Sprains and Bruises. 



Sold by all Chenuste, Get the genuine.' 



[Advt. 



