Feu. 10, 1882.J 



KNO\VLEDGE • 



327 



regarded as intended to explain away miracles. We eipect fairer 

 treatment than tliie, however, from our readers, whatever their 

 religions views may be. The word "Simian," when referring fo 

 the s|wcies, always has a capital. As for "extraordinary," does it 

 mean extra-ordinary in yonr sense — that is, exceptionally ordinary ? 

 Always thought it meant something outside of what is ordinan,-. — 

 \V. Greenwood. If the air in bladder is much compressed, there 

 will be a slight excess of weight ; otherwise none, unless weighed in 

 vacuo. — F. CoWLKV. Yon are right in saying that we do not 

 see a star where it actually is, if the star is in motion, 

 though, owing to the much more rapid motion of light 

 than of any celestial orb, we always see a st.ar very near (appa- 

 rently) to its true place. But you aro quite mistaken in sup- 

 posing that owing to the earth's rotation, the star's tme place 

 might be in the southern celestial hemisphere when we see the star 

 in our northern skies. The earth's rotation has notliing to do with 

 the matter — atUast nothing in the way imagined. Compare the 

 earth to a twirling globe in a room, against which a number of small 

 shot are shot from a distance. The globe may have made several 

 twirls while the shot were travelling, and the side turned towards 

 the gun when it was fired may be on the opposite side when 

 the shot arrives, but the shot will reach the s^ide which is at 

 the moment of .arrival towards the gun ; and, in like manner, 

 rays from a star reach that side of earth which is towards 

 the star, so that rays coming from a star really in the southern 

 celestial hemisphere cannot possibly reach a part of the earth turned 

 towards the northern celestial hemisphere. In other words, wher- 

 ever a star's rays reach the earth (that is, wherever the observer 

 maybe), they will seem to come from the direction in which the star 

 lies, apart from the .slight corrections due to aberration, &c. The 

 suggestion that expensive telescopes and microscopes might be let out 

 on the three years' system seems worth considering. — F. F. Read 

 article by " Fellow of Astronomical Society," in No. 10. — B. Riley. 

 Your method of computing the moon's distance from the force of 

 gravity, as calculated for the moon, combined mth moon's known 

 period, is simply working Newton's problem backwards. It is indi- 

 cated at p. 21-2 of my Treatise on the Moon. — 1'. A. The lecturer was 

 quiteright, so far as a.^tronomy teaches. I have for several years given a 

 lecture bearing the same title and treating the .^lubjoct in the same way. 

 Hatter may be infinite, but it does not follow th.at each sun in space 

 can draw to himself an infinite quantity. — Vice-Apmieal, F. A., &c. 

 Thanks. The efficacy of oil as a sea-calmer has been warmly advo- 

 cated by Mr. W. Chambers, in C}wmbers' Journal. Believe the matter 

 rtill remains in donbt. Have not room for the long extracts sent 

 both by F. A. and VicE-AnMiRAL. — J. J. Your method already 

 considered in the earlier numbers of Knowlepce. — Farmer Will. 

 Sorry to hear you say you have a " fossilised mind," but your belief 

 in Noah is scarcely of scientific importance. Permit me to quote one 

 aentonre of your letter : — " Before Noah's time we read that there 

 ■■•^s a certain tree" the taste of whose fruit brought trouble. "In 

 )>ing knowledge we eat of that fruit." Will adverse critics, if 

 !i there are, remember? — J. II. TI. I can answer from my own 

 ..i,.servati(m that all the objects you mention can be seen with the 

 smaller apertures, powers, &c. Probably the faintness of green or 

 blue stars m.ay be due to the quality of j'our glass. The diffraction 

 rings not being complete circles does not indicate very serious defect. 

 Wish your letter were a little more compact, or your queries put 

 separately, in proper query form. — B.M., F.R.C.S. You write under 

 evident misapprehension as to space at our command. But thanks all 

 the'same. Surely the Osborne sca-ser]ient case did not occur so many 

 as "eight or nine years" ago. Which questions would better suit 

 the Lancet. We do not at all want medical questions; but unless 

 yon call the quicksilver question medical, nonesuch have appeared, 

 — Arthur Twobt. Light from each point in the small triangular 

 space gives circular image of stin, and these overlapping, combine 

 into a single circnlar image, in which the triangularity of small 

 aperture is lost. — A. J. Mabtix. It was a slip of the pen on the 

 part of " Five of Clubs," which he corrected in the next number. — 

 E. J. Wilson. Do not know any better work on trigonometry than 

 Todhunter's. — J. A. Ceawlev. Thanks for quotation from Tacitus, 

 showing that Tiberius was of the same mind as author of " Brain 

 Troubles " : " Politusqne eludere medicomm artes atque cos 

 qui post tricesimum £ctatis annum ad internoscenda corporl 

 suo utilia vel noxia alieni consilii indigerent." — E. D. G. 

 1 Thanks for numerous replies and notes. If Knowledge 

 1 could liut be expanded weekly to 48 pp. or so ! Replies not 

 I mentioning number of quen,- are useless to us. — J. 11. Garfit. 

 1 Fear I can only say the ai-ticle was too long. When any circum- 

 ', stance assures us that an article will not suit, our attention is 

 i naturally turned at once fo "the next article."— J. Bae. Who- 

 t erer reaches the Pole will probably have to winter there. For him 

 ■ there are many tvays. — J. .T. Henderson- wants titles of books on 

 chemical analysis of alcoholic stimulants. — J. W. C. That would 

 he right, if tou have correctiv determined focal length of the two 



glasses. Bat a 2-inch aperture would not readily bear suoli a 

 power.— W. Baxter. Ferguson's tables no longer of any value. 

 Trj- Johnson's book on eclipses. — Graoatim. The paradox comes 

 in before the Pole is reached. The time is finite, but the number 

 of convolutions infinite; how, then, can tho particle bo said to 

 reach the Pole (along what course, I mean) ? Thanks for 

 other matter, but no space except for qnerj'. — It. W. Dr. 

 Brewer's explanations amusing. " Why does sun put out fire? 

 Because the chemical action of sun's mys is detrimental to com- 

 bustion ! Wliy does a poker across a fire revive it ? Because the 

 poker concentrates the heat ! " Just so. This sort of science -teaching 

 might go on for ever. As thus, why do the planets travel in ellipses? 

 Because the tendencies of planetary motion are elliptical. Why do 

 comets bring disaster to nations ? Because of the disastrous ten- 

 dencies of comotic apparitions.— A Stuiiknt No. 1. Vouaskusto 

 reconcile a statement made by Dr. Ball with another made by the 

 Astronomer Royal for Ireland. Dr. Ball says in one lecture, there 

 is no water in the moon ; the Astronomer Royal for Ireland, in 

 another, says tidal waves checked the moon's rotation. But Dr. 

 Ball said in the latter lecture that such waves would exist whether 

 there was water or not in the mosu ; and in the former lecture tho 

 Astronomer Royal for Ireland said that formerly there may have 

 been water in tho moon ; while finally yon are not to sujiposo that 

 Dr. Ball says one thing as Dr. Ball and another as Astronomer 

 Roval for Ireland. This you will have opportunity of rocoprnising 

 shortly in an article which ho has written at our request for Know- 

 leoce. — A STtroENT No. 2. Stimulants certainly not good ; the 

 other matters depend on the health, strength, and constitution of tho 

 student. — B. Your vernier reads mrro closely by being so divided ; 

 .adding the extra divisions is equivalent to bisecting thcdivisionson'.the 

 limb.— G. G. D. Measured from true noon, tho change is equal on 

 either side, but mean noon slightly differs from truenoon. Read any 

 text-book account of equation of time. Fully answered in ordinary 

 explanations of the calendar.— F. II. R. Edinburgh is so often 

 pronounced Edinburg, that custom may be regarded as at least 

 justifying the practice. In Scotland I have seldom heard it, but 

 always Edinbro', among tho less educated often Kmbro'. — W. 

 Wilson. Cannot see how a scientific theory can depend on tho 

 merely verbal questions you raise. I would rather, for my own 

 part, say, " I see the house," than, as you suggest, "I see the 

 vibrating ether ; or, I have received on my consciousness, through 

 the retina, tho optic nerves, and tho brain, an impression by 

 vibrating ether," indicating tho existence of a house, &c.— Gkralo 

 Massey.— The motion of the apsides does not affect the preccssional 

 period. It shortens the interv.al between the epochs when spring, 

 or any other fixed seasonal point, coincides with perihelion or 

 aphelion, but tho spring equinox makes the circuit of the ecliptic lu 

 the period of about 25,870 years mentioned in books on astronomy. 

 —J. A. Dobson mentions that Drew's Geometrical Conies is suffi- 

 cient for a first clas^ in fourth stage at Kensington.— M. II. P. Tho 

 dream theory of your lecturer has no scientific basis. 



ILfttn*^ lUrcibtli. 



T. V. II., A. Ailkcn, Acacv, S. de M.. .1. B. Diml.leby, E. M., 

 J. C. II., F. W. Beckett, J.'R. U., J. J. M., Isaac Isaacs, Cosmos, 

 Charles Gray, X., Amicus, G. A. L., J. A. Miles, Magic Squares, 

 Student, (not A Student), Vega. 



^ottsi on art anil ^ricnrf. 



Ax Electbical Stati-be Alarm.— .\ curious application of elec- 

 tricity is described in La Ltiinicre £lectrique. It consists in a 

 device to prevent military conscripts practising frauds as to their 

 stature by bending their knees. When the youth stands erect 

 against the measuring post, the hind parts of the knees press on 

 electric contacts, causing two bells to ring; the ringing ceases when 

 there is the least bendintr. The sliding bar which furnishes the 

 mea.sure has also a contact^ which is pressed by the head, whereby 

 a third electric bell is affected. For a correct measurement, the 

 three bells should ring simultaneously. This system, tho invention 

 of M. Cozala, is now employed in the Spanish army. 



Capacities op Lungs. — Dr. Nagorsky, having measured tho 

 capacities of lungs of 630 boys and 314 giris in tho schools 

 of, the district of St. Petersburg, now publishes tho results of 

 his investigation in a Russian medical paper, the Hnrr/ron. lie 

 has found that the rapacity of lungs, in relation to the weight of 

 the body, is 65 cubic centimetres for each kilogramme of weight in 

 boys, and 57 cubic centimetres for giris. The law of Quetelet being 

 that, with children below fifteen years of age, the weight of the 

 body is proportionate to the square of the height. Dr. Nagorsky has 



