36G 



• KNOWLEDGE • 



[FEa 24, 1882. 



iitUintioii to tho oquiluloral triangloN, wliieli load you nwity frnm 

 t nip Molii lion. NoUi only that tho cmtri'ii of thoHi- lire ccntn'H of 

 iirra on IrianKlc'H hulon contaiiiinK |i'u<'li an iin^^li' of tlO ili'i^nn-H. 

 Throu)(h untie A of (riiiiiKlu ilmw, to nii-pt urcH on AH, AC, line 

 I'AQ piuikllol to lino joining; <M3nlri'8 of tlioBo arcs. PQ in the 

 inaxiniiini xtnuVht lino whioli cnn be ko drawn, hot I'll nnd (j() 

 producod uii-ot in It. I'QIl is llio muxiniiini i<c|nilatornl triniiKlo 

 which cnn bo dcHcribcd about A IK'. IIimk-o I'll iiml QR nr<- imnillrl 

 to linos joininf; rrntrcs of Iho nlhor piii™ of iiriy (for oihcriviBP a 

 larjfor cnuiluti'i-nl IriiinRlo could lio drawn, and one Bide of tliiH 

 would 1k' a l()i.:,'ir clioi-d tliun PQ, which in impoiwiblo). llcncc, 

 the trianiflo fiprnn d {,y joining ronlrc» of thoao circular urcK hat) itK 

 sidoH panilld t.. hides of triunglu I'QH, and in thcreforo equilateral. 

 OswAi.n I)\u.Mi.\. Tlinnks. Como in oarly with delinition.^, and 

 you will bo very wilcomo. I quite aRroo with you that nt the 

 boKinniug of :iMy di»cii>.>.ion sound definitions arc very important. 

 Vo8, Professors King and Rownoy woro the opponents of Eozdon 

 Cauadcnso. Twas thny of whom the poet (that good follow 

 Hroutrh) wrote in 18C9:— 



And through tho list.i a cry has flown — 



A daring chullongo for a fight — 

 " Eozoon, bo it known, 



Has structure like the nunimulitc ;" 

 And on bi-uvo Dawson's gauntlet warm 



Is dimly traced in mystic line, 

 "Outline of film aabestiform. 



And chambers all acervniine." 

 But hark ! a loud, defiant shout 



Resounds from Connaught's distant strand : 

 The King of Galway has sot out, 



All niail'd in ophite, pen in hand ; 

 And to the field he hies him straight. 



With gentlo Uowne_v, knight rcnown'd, 

 Whose prowess none will underrate 



On Chemistry's broad fighting-ground, &c. 

 — M. M. The size of the moon'.s image formed at focus of object- 

 glass having -t2 inches foeal Icn<;th, will be about o7-75 inches, as 

 you can readily prove by directing the telescope to moon, removing 

 oye-piecc (and, if necessary, eye-tube also), and receiving tho image 

 on a piece of card or paper. But the magnifying power depends 

 ou the eye-piece, and you cannot say the image will have an 

 apparent diameter of so many inches, but subtending such and such 

 an angle. With a power of 100, for example, the moon's apparent 

 diameter would subtend an angle of about 3,100', or nearly 52°. — 

 Eloa reciuiros information as to management of gold fish in glass 

 globe, average duration of their lives, &c. Captive balloons (this 

 refers to a different subject, let me explain) might certainly be 

 sent up with minimum thermometers, to determine temperature 

 of upper regions of air. — Simplex. Quite so: but now if you 

 would compare some of the symbols. Is'early every stenographer 

 knows Pitman's; I use it myself, though not for reporting. 

 Could yon not give us ocular demonstration of the supe- 

 riority of Bell's system.— Sir T. W. Letter sent at once 

 to publishers.— C. Lloyd E. Pardon me, but I was thinking 

 of another correspondent. Your evidence about the poker is 

 balanced by an eipially wide experience the other way. But why 

 should 1 bo prejudiced against tho poker-across-fire theory ? If a 

 theory so remarkable could be established by the rough kind of 

 evidence you adduce, it would be a delightful subject for Know- 

 LKUGE. As it is, it only illustrates what men can believe, and 

 Herbert Spencer has already used it in that way. — R. C. Your 

 difficulty is a natural one. Yet notice that every part of an 

 ellipse is concave towards centre, or towards either focus, despite 

 the increase and diminution of more distance. If you draw the 

 moon's path to scale, you will see that it is concave towards the 

 sun all the time. Describe two concentric circles rather loss than 

 a quarter of an inch apart (''H inch), and baring radii of 92 and 

 92i inches respectively, and divide their circuit into twenty-fivo 

 equal parts. Then tho moon's path would be represented by a curve 

 passing from the outermost to the innermost, and then to the outer- 

 most again, and so on, the successive contacts occurring at the suc- 

 cessive divisions along the outer and inner circles alternately. — Tita. 

 Will try to find space shortly both for letter and extract ; meantime, 

 lot mo note that you seem to me to bo quite right. There seems to 

 be as much scientific accuracy in tho account as in tho blind man's 

 statement that rod was like the sound of a trumpet, or in the 

 association most of us have had as children (and, perhaps, still 

 have) between the days of the week anil particular colours. For 

 instance, with me Sunday is yellow, Mondav rich red, Tucsdav 

 olive green, Wednesday bright green. Thursday dark grey, Friday 

 orange, and Saturday light grey. The months have .-ilso their 

 colours. — J. Rak. If you had dmnced to read my accounts of 

 Arctic travel, you would know 1 did not need to be informed of 

 what you kindly (ell mo. It will be time enough when tho 



Poll! ia reached to loam how long the oxplorerH will have to 

 Hi ay there. You «ee, I give you nnollier opjiortunity for 

 contradiction, which seems your Htnmg suit; but you ah'iuld 

 try to make out what you arc contradicting. — B. We have 

 not used an instrument haring a vernier divided as you descrilw; 

 but it Hocms obvious that it would serve to divide to one- 

 half the arc to which tho older form of vernier will divide. Thus, 

 when you have the vernier divided into OOths of 59', you take tho 

 division nearest to one on the limb, and so got the reading true to 

 a second of arc. Now with tho vernier divided into GOths of IW, 

 you can either take tho division nearest to one on the limb, or 

 noting that two divisions on the vernier are appreciably equidistant 

 from the divisions (alternate) on the limb, you regard the bisection 

 of tho space between those two divisions on the vernier aa 

 coincident with the division midway between the two on the 

 limb. You read this just as easily as yon would if tho 

 hisection woro marked on tho vernier. Uenco it is as though 

 the vernier were divided into 120th8 of US', enabling yon 

 to read to half seconds of arc, instead of to seconds only. — 

 Etai'h. No truth in the report, but thanks. — A Subsckibeb. Odd* 

 in favour, as you say. It seemed too obvious to need correcting. 

 East and west in star maps right. Yon look down at earth, up at 

 sky. Uenco tho difference. Evidence about pink tinge of oahes, in 

 fire gone out in sun would be interesting. — Why ? oh, why will not 

 " A Subscriber " follow rule, and give number and page of letters ? 

 — Farmkk Will. Your queries will not go under any heading wo 

 can invent. If you do not tliink them worth heading, can you think 

 them worth inserting ? You say, in the midst of your queries, that 

 if the doctrine of evolution is true, the doctrine of fate is also true. 

 What is the dotftrine of fate ? Why not say, as you may with equal 

 reason, that supposing trees and animals really grow, and are not 

 changed from state to state by special acts of creation or change, the 

 doctrine of fate must be accepted ? — T. A. " I do not know how it is, 

 but at present 1 like my hypothesis the best, it seems to my poor judg- 

 ment the nearest the truth." Most of us feel that way. But, as you 

 very truly say. Who can thoroughly understand these things ? If 

 we had not so much to insert about things we can to some degree 

 understand, wo might take up these inconceivablos. — Hakbd was 

 dazed three days " by Magnetism ? Astroism ? Divine Effluence ? " 

 We do not know ; but infer, it was on one of those days that he sent 

 us advertisement of " The Magnetic Pilgrim" who " tarries top of 

 IJunyan Street." — Jonx T. Page. The practice of collecting auto- 

 graphs is not childish, far from it : nor is a toothache a joy for ever, 

 very much the reverse. — Hox. Sec, Civtl, and M. Engixeeb's 

 Society. Mr. Love's paper was marked for insertion, but crowded 

 out by press of matter requiring more immediate attention, — and 

 more concisely written. — J. Kirkmax, M.A. Questions now 

 answered. But would it not have been an inaccuracy to have, in 

 first act of Harold, a reference to " Arcturus dancing so 

 brightly, almost through the nucleus of Donati's comet in 

 1858 ? " not that Arcturus danced, or seemed to dance, at 

 that time — to my eyes any way. — • T. J. H. Matter too 

 complex to be adequately treated in short notes, and no 

 room for long ones. — Hygeia. Fear the ill-effects of tight-lacing 

 and high heels are as well known to the tight-lacers and high-heelers 

 as to the rest of the world. Articles on the subject would be thrown 

 away on those, and are not needed by these. — Alpha. There is no 

 reason for supposing that there has been, within the last few 

 centuries, any perceptible change in our northern climate; but, if 

 there had been, the displacement of the Polo Star by precession has 

 nothing to do with it. The inclination of tho earth's axis to the 

 jilane of her path does not vary in any such way as to aSect 

 climate. — Axti-Kreopihgist. I do not think any flesh-caters so 

 ignorant as not to know of the wide range of food materials open to 

 vegetarians. I am not myself a vegetarian, but at a time (three 

 years ago) when I did a great deal of mental and bodily work 

 (rowing every morning two hours at my hardest, and often in heavy 

 rain) I used frequently, for several days in succession, to take no food 

 but fruits and vegetables — not on principle, but from sheer careless- 

 ness : and I cannot say I ever felt the least failing of strength. I never 

 had better health. My tastes, however, are of the carnivorous kind, 

 or rather, they are for our customary mixed diet. An Abernethy 

 biscuit and a bnnch of grapes will servo mo for a dinner, on occasion, 

 very well ; but I do not " hanker" for such food. 1 mention this, 

 not as of any interest in itself, but to show that if fruit and vege- 

 tables agreed with mo so well, it w.as not because I liked them (so 

 that the evidence in their favour is so much the stronger). — A. H. E. 

 Nos. 2 and 3 are not out of print. They might be picked up, 

 perhaps, after a little inquiry ; but 1 know of no place where they 

 could bo obtained. A few copies remain of Part I., in which aro 

 those numbers, and a limited number havo been kept for our 

 volumes. It would be useless to reprint them, as many others of 

 the earlier numbers aro nearly sold out too ; so that if reprints 

 wore ordered at all, at least eight uumbers would havo to be ro- 



