J26 



♦ KNOWLEDGE • 



[KKa 10, 1882. 



(boptinnprs") type-writer recently bronf;)it ont in America. — E. 8. 

 Dr. Ball (whom wr have invited to write for uii on ttio irah- 

 jerl, and who hns kindly dono fo) in <|nitp ri^tit ; the enerjfy 

 of a Ixxly in rfti»inK tidnl wnves vnricB directly IIB tli'o 

 mnsa, and inversely a.i the rnbo iif th" dixtnnec ; thnt in why 

 the hinnr tide errecdn thnt mined by the Hnn (which, wero the 

 mtio thnt of the inverno Rqnnre, would ho the (freator). W. I'. 

 Thank* ; wo hnvo toncliod on the point in our nrticlo on " Fnlln- 

 cien," now in type.— EnMitvp Hint. Ilofore we ro to the expense 

 of engraving yonr diiigmm, we mnst Imvc snme idc.i of the nature 

 of the relations you propose to doni witli. As it utands, it looka 

 like " n lionst." We p'vp it without a nprnre, nnd in our own words, 

 in the Mathcmnticnl Column ; but we should not cnre to nttack it 

 nnlesa we saw onr way to some nseful rrsnll.— H. A. Htllkv. Ik-I 

 ng rest, ftft^^r mapic squares, before wo begin on magic circles. — 

 W. 11. Many thanks ; your alRebraiciil solntion very neat. — A. N. 

 SoMEB.xcALES. Thanks; but the projection not likely to interest many, 

 and Bpnco rnns short. The polar aspert of the heavens appears.— 

 A. T. C. When we wrote "any rectanslo," we meant, as nsu.il. that 

 the solution mnst be applicable to any nclaufjleof whatever dimen- 

 sions, not that you might take a rectangle of any particular dimen- 

 sions which seemed most convenient. The question related to 

 I.H.S., pat on tombstones now, not to the ancient inscription in 

 Oreok letter.'!, I.H.S.— C. J. C. May shortly describe a very simple 

 instniment, by which the place of Venus "in the day-time may be 

 found.— E. D. a. Quite nnabie to find place for what you rightly 

 describe as a flood of notes. Broun-Seqnard was the name of tho 

 physiologist yon refer to j but ho did not ^vrite tho .article ; ho was 

 qnoted in it among other authorities. I wrote the article myself. 

 Tho difficulty about recommending liooks is that tho practice 

 is open to abuse. — J. WniTr.KV. Depends what size field 

 you require. It is impossible to answer questions so vagiic.— R. 

 Stavely. Thanks. But yon get tho vrrong cqnation to escribed 

 circle. Tlie negative sign under the first radical is incorrect.— 

 W. G. RoLFE. Astronomers are not at issue with geologists as to 

 the earth's interior volcanic ashes carried by winds. In my article 

 on OArth-bom meteors, I have shown how meteors .sent beyond the 

 earth's control would still travel on paths intersecting the earth's 

 orbit.- A. M. K. T. Ton are quite right. I have written repeatedly 

 to show that the only danger was for the comet, which, in such 

 »B encounter, would be like the " coo " of tho elder Stephenson. 

 —A. Jellitax. Never heard of any astronomer so named, bnt 

 Prof. Pntchard may bo writing about the stars.— R. E. J. Tlint is 

 just what I did take into account. If facing a windmill, the 

 left arm alua<js goes down, it follows that if the windmill face's tho 

 north, and yon, facing it, look sontlnvards, the eastern ann goes 

 down. On the other hand, if you look northwards in facing it, the 

 western arm docs down. Why the left arm should be made to 

 go down and the right arm up, instead of the revcrs'o holding, I do 

 not know.— rniT.0. Brackets are far too useful to be limited to 

 the use to whicli Whately put tliem.— G. B. Thanks, but first set 

 of hogs sufficiently attended to.— A. Gactiert. The Chinaman said 

 he was a member of a class of trained computers, and not one of 

 the most skilful.— G. M. T. Bates. It seems as though, since 

 there are -162 combinations of six girls, and each set of 

 five out of the six .appears six times — viz., with each 

 t Vi% remaining six of the eleven, there must be one-sixth 

 of 462 sets fulfilling the conditions, or seventy-seven. — G. JI. If 

 yon wait till I prophesy, you will liave to wait more than fifteen 

 years.— Winter. The time of Venus's brillianev is to bo calculated 

 not taken from the " Nautical Alm.anack." Vou have not got the 

 answer quite right to the watch question. The watch loses five 

 mmutes in a day of twenty-four hours, and the interval from noon 

 at one place, to noon at a place IT due west of it, is more than one 

 day.— J.C.L., G.F.H., Geo. Brown, Araitciiexs, C.T.B, and others. 

 Thanks for notes on the quicksilver matter.— Insomnolexs. Yonr 

 night-wntching calculation of the sun's restraining force on 

 earth, measured by tensions of snn-attaclicd wires, is ex- 

 cellent. Wish we could find room for it. There is no doubt 

 now on the general subject of liglit. Sound ceases to be 

 perceptible when the vibrations are very rapid, and a very wide 

 gulf separates the most rajiidly vibrating 6ound-w.aves from the 

 most slowly vibrating light-waves. The waves are also different in 

 kind. To s.ay tnitli, one might almost as well ask, Wlir, since water- 

 waves rock ships, do not sound-waves also rock them ? aa your 

 question. Why, since vibrations of a certain velocity produce sound, 

 light-waves are not also heard ?— HE.sK-ETn. A theodolite would not 

 help yon much fo End a star or planet from the R.A. and Doc. in 

 the Nanlirnl Almanac. Yon can calculate bv spherical trigo- 

 nometry the altitude nnd azimuth for a giVen epoch ; but 

 a fresh calculation would bo w.antcd after the epoch was 

 past. Tho best way is to use an equatoriallv-raounted tele- 

 scope. Of course, if the object is conspicuous, you can 

 mark dowu its place in a star chart, and then readily iden- 



tify it in tho constellation wherein it is. — S<tKNTi« Amici-s. 

 Querj- why birds scmtch their headii, rather too snggostive of l/ord 

 Dundreary's " Why doth a dog waggle hith tail ? " — CncBCiiMAN. 

 Thnt is just one of the qnostiona wo do not winh asked of the 

 students of science to whom they refer. What they think of tho 

 origin of man is clear. If they think this inconsistent with other 

 views, wo do not wish them to say so ; therefore, we do not wish 

 others to ask them if they think so. — Jah. OBirNnr. When a jx-rnon 

 who has had small-pox, or hag been vaccinated, in again attacked, 

 it is not tho revival of the former disease germs which is in quci- 

 tion, bnt the introduction (in some way) of new germs into the 

 system. Vaccination is supposed to act as a f»erfect protective for 

 about seven years. Germs, however, may lie dormant for years, aj 

 we see in such cases of infection as arc discussed in Tyndall's book on 

 " Dust and Disease." — Ubsa Major. 'ITic rule is — nnml)cr of feet 

 fallen in ( seconds, equals IGl x sqnaro of ( ; so that in G seconds a 

 body falls through G times 30, or 210 feet.— J. .Siiabp. Observations 

 snch as you cite are not of snfficicnt exactness to admit of scientific 

 discussion. It is no proof of spontaneous generation to ask. If snch 

 and such living creatures were not evolvol in the places where 

 thej' are found, whence 'came they. In manj' cases, where tho 

 origin seemed more perplexing than in those you cite, Pasteur and 

 others have traced the complete chain of linked existences. — 

 Gravity. The difference in tho range would not bo so great a* 

 tho parabolic theory would suggest, the resistance of the air 

 greatly affecting the range; hut there would be a decided 

 ilifference of range. If both guns were fired at the same time, 

 then, when the lower projectile had descended to the ground, the 

 upper would have attained as great a horizontal distance, and be 

 still 100 ft. from the ground ; it would not be ilcscending vertically, 

 the range continuing to increase, though more and more slowly,* 

 till this projectile in tnm reached the ground. — A. E. S. Thtl. 

 question was answered on page facing the answer to other A. E. S^ 

 — J. A. S. B. Too big a cpiestion. All perturbations have to bi, 

 considered, besides mathematical relations of a complex kind. — H. 

 R. Welleb. Thanks, but room for only one answer to the ques- 

 tion. — C. E. II. By a sine qui non is signified something witl*-_ 

 ont which a certain course w^ill not be followed ; the words mi 

 "without which not." — 1. .1. .Simpkin. Thanks for the co: 

 tions. The article was too technical for the "remler" and for 

 readers. It was sent to the printers by mistake for another. — Rl 

 W. ,1. W. Many thanks. — Constaxs. Nay, tho poker, if — as 

 — cold, in the first instance will do the reverse of what yon saggesk 

 If finally it gets warm, its warmth has been taken from the fix* 

 which it is supposed to nourish. In the other case, we know wl^ 

 less light readies the eye in full snnlight. Stay in the dark awhile^ 

 with a small mirror in your hand, facing the blind which darkens 

 the room, and while .a friend draws up the blind, look at the pupils 

 of your eyes as seen in the glass, and you will see the reason clear^ 

 enough. Can see no reason why with spring tides the sky should 

 always become overcast ; though, of course, thcro is then a widsr^ 

 water surface for evaporation. — Jonx Saxpers. The points of light 

 are simply the images of .Jupiter itself seen after doable reflect 

 at the front of the glass as well as the back. Children have been 

 snfFocated by cats sleeping over their f.oce, not by cats drawing,; 

 their breath. The secret of such criticism as that in the Manchester 

 f<portinj Chroni'-h is to be fonnd in my condemnation of sporting 

 rascaldom, not in my predictions of unpleas,ant things. It is veiy 

 well known I have predicted only snch things as meteoric showers, 

 &c., which have usually occurred as predicted — unlike what sporting 

 pro]ilicts predict ; praise from sporting prophets would be like the 

 contempt of honest folk. — J. P. Saxdlands. Sorely you are a 

 little unreasonable. Certain readers ask for intermediate forms, 

 saying that if there is descent, such forms should exist. Dr. 

 Wilson describes some. You then s.ay they do not prove descent ; 

 and I reply, naturally, that he wrote in response to those who 

 thought such evidence as Dr. Wilson supplied essential to the de- 

 velopment theory, and not for ono who, like yourself, considered 

 that it proved nothing. Now you s.ay that Kxowi,edgk, being in- 

 tended for those who want information, contributors should write 

 for those who, like you, want information. Are we, then, to answer 

 no questions until we are assured that every reader of K.vowlepcS 

 wants the information asked for by some of them ? It would 

 interest me to know how my article on ** Fallacies about Luck" 

 touched on religious questions. In one sense, everything almost 

 that could bo said hero might lie regarded as touching oni 

 religion. The statement that two and two make four, involTing 

 as it does the inference that two and one make three, might be 

 regarded as verging on a reference to the diverse doctrines held by 

 Trinitarians and Unitarians ; remarks on Itrain Troubles might bei 

 considered to refer, more or less directly, to theological interpreta- 

 tions of " possession by spirits ; " Dr. Carpenter's <li,qcnssion of Food; 

 questions might lie held inconsistent with the Bible narrative of the, 

 baskctsful of fish ; and Mr. Foster's articles on Illusions might be 



