Nov. 24, 1882.] 



• KNOWLEDGE 



423 



gnstorrs Uj Coriespontjnitg. 



Hnrrs to Corkbsponde 



thtfo 

 uMicer to pricate inquiries. 3. Correfpondentt fhoiild temte nn _ 



paper, and put draftings on a separate leoj". 4. i'l/cA letter should have a tif'e, ttvd 

 in replying to a letter, r^erence should be mttde to its number, the page on lehich it 



E. S. Thoese. I quite agree with you. Xo man wlio has 

 «Ter walked past that Kew wall should fail to do all that 

 in him lies to get it replaced br a railing. I do not 

 live in a house overlooking the srronnds, but if a subscription is 

 opened to raise the necessarr sum, I will gladly put down mv name 

 for £10. But Sir J. Hooker would infallibly resign if Goveirament 

 agreed to such a change, and what would old England do then, 

 poor thing? — F. S. L. The question related to a garden-walk, and 

 though a circle is, as you say, one of the limiting forms of the 

 ellipse, a circular walk would not therefore be regarded as an 

 elliptical one. — W. H. Tatloe. Thanks; but medals are apter 

 rewards for prize pigs than for men. — J. Spiee.s. I should only be 

 too glad to have an excuse for visiting old Ayr, where I passed a 

 very happy half-year. — Poor Student should note what sort of 

 work he wants the spectroscope to do. For some very simple 

 work, a slit and a prism, with a blackened tube or so, would 

 serve very well ; for other work something more elaborate must be 

 made. — W. S. P.uitt. That light theory of comet's tails is not 

 only foiled by multiple tails, bat by curved tails, thwart streaks, 

 and other phenomena. But it will not do anyhow. It has been 

 tried many times, and never woiJd fit a single case. — Gradatim. 

 I write away from my books (lecturing at Newcastle), but you viill 

 find in De Morgan's " Budget of Paradoxes," \/2 to 110 digits. 

 There are two digits which appear only S times, and digit 7 

 appears no less than 18 times. But you can try this experiment : 

 Take out a list of digits at random, by opening a book of logarithms 

 and bringing down a pencil point at random in the open page, 

 marking down in your list the digit nearest to the point marked. 

 You will find nearly always among the digits thus taken out, one or 

 two which get the lead in numbers and keep it, one or two which 

 fall behind and keep behind. It is because there are so many digits 

 that the chances are one or other will be, as it were, lucky in the 

 <lrawing, and one or other unlucky. Of course, the mathematical 

 question is dealt with by comparing, for n trials, the sum of all 

 the co-efficients in the expansion of 



in which the power of amj one of the terms falls short of m-^10 in 

 a given degree at least, with the sum of all the remaining co- 

 efficients. — W. S. BB.4DLEY. About the comet, shortly ; but wo 

 (students of science generally, I mean, not " we " editorially) know 

 much less about comets than" we should like to. On the other point 

 — the bet was an idle one ; but he might have safely wagered his 

 £50 that no one could convince him the moon was not "perfectly 

 stationary, and never moves from place to place."— "Taranaki."' 

 The evolute of a circle is a point — the circle's centre. The evolute 

 of a straight line is either of the points at infinity in direction per- 

 pendicular to the line. — H. De.vxys. I must "ask " Mephisto." 

 — An Invalid. We should certainly recommend you to have a 

 tire ; but we are not medical. — I.vqisitive. I forget what par- 

 ticular defeat of the Spaniards is referred to by Browning in 

 the poem you mention. — K. h. McGrath. Let us consider the 

 point logically, if your wrath, which really seems blinding, will 

 permit yon. You say, '• Kerdic was a pirate," and " Eollo was 

 a pirate ; " you count me out your ten murderers and eleven 

 imbeciles, cite Richard Sans-peur and William the Conqueror 

 himself as of illegitimate birth, and William of Lunebcrg, George 

 III., and a third, as subject during parts of their lives to attacks of 

 mental aberration. Then you ask mo if I " dare to deny that the 

 parable related to them." I dare say not, if you dare say so much. 

 But either yon are right in all your statements, or yon are not. If 

 you are not right, yon should hold your peace ; and if you are right, 

 I cannot be far wrong. As to your strongly-expressed wrath, I can 

 cmly say, God keep you in your present mind, for you treat your 

 friends ill. "Call yon (/la*' backing of yonr friends?" If so, I 

 would rather not be "one of them.— F. Foot. It is quite true that 

 tho obliiiuity of th« Ecliptic has changed since the days of the 

 first astronomers. This is due to the di.^turbing actions of the 

 planets by which the path of the earth has been changed ; in 

 other words, the position of the Ecliptic itself has been changed, 

 not tho axial pose of tho earth in space. — D. Ma.vweli.. Is 

 not that rather what one would expect, than the reverse? Tho 

 result in Tyndall's experiment is what one would not expect ; but 

 where tho close packing of the particles is done away with, as in 



your experiment, one would expect its effects to be corrected too. 

 — S. D. I use Chauvenet's "Astronomy" for the purposes you 

 name. — S. Staxdeixg. Oh ! give us a rest : or write about matters 

 less difficult. Metaphysics is not in our line. Besides, yon spell so 

 erratically, it is hard to know what you mean. — M. D. Uranus 

 goes the right way round ; it presumably rotates the same way as 

 its satellites, but its rotation has never been properly observed. — 

 G. T. Ky^'es. I quite agree with you about the comet; it is very 

 difficult to get engravers to attend to such points closely. It is 

 now not likely that the comet will return anything like so soon as 

 had been thought. The poem is capital, all but the too compli- 

 mentary adjectives applied to Mr. Proctor. — E. J. H. Those figures 

 on p. 34-t ? Which figures ? If you refer to my figures about the 

 Egyptian signalling, they are nearly correct. The depression for a 

 mile is rather less than G in. when correction is made for refraction. 

 Sidereal time is measured from the time when the first point 

 of Aries crosses the meridian. Now, on March 21, if sun at first 

 point of Aries at noon, the sidereal time at apparent noon will be 

 h. m. Os. ; but at mean noon, which is six or seven minutes 

 earlier, sidereal time is some six or seven minutes earlier too, or 

 23 h. 53 m. or 54 m. — Debate. Do not know where you can find 

 any account of the failure of justice through the incorrect findings 

 of juries. — E. Gereish. The quotation will be found at the end of 

 my " Universe of Stars." — J. wants the solution of the following 

 problem ; To describe three circles in a triangle, each circle 

 touching two sides of the triangle and the other two circles. — 

 A. Shepherd. The reflected bow in such pictures is manifestly 

 wrong, but if you draw the angles correctly you vnll find yoiu* 

 smaller reflected bow could not be given. — A. C. It is of little nse 

 to look at Neptune with a 3-in. telescope, though you can see it. 

 The "Nautical Almanack" gives the place, which you can mark 

 down in any good map. — R. C. Tayloe. A sovereign contains 

 113-001 grains of gold and 10-273 grains of alloy.— E. R. Cowley. 

 Those questions, to be properly dealt with, would require all 

 the space in a volume of Knowledge, and much very pro- 

 found reasoning and calculation. — W. B. Phillips. Jupiter has 

 been in Gemini lately. Certainly Venus visible as an evening star, 

 and rather a bright one. — G. Gareatt. Do not know where the 

 results of the observations of Mars in 1877 have been collected. — 

 C. W. G. Thanks.— E. Gschwind. A very noteworthy observa- 

 tion : we should be glad to learn whether any other noticed the 

 passage of a meteor apparently from tail to head of comet at 5.17 

 on the morning of Nov. 8. — F. H. M. wishes to know whether 

 trapped animals are unfit for food, owing to blood-poisoning, re- 

 sulting from their death agonies. — Nil Despeeaxdvm. Want of 

 practice prevents some from winking without blinking. Try again ; 

 only not when ladies are passing. — J. F. You should get Mr. 

 Pearson's book on the tides. — Unit. Consider the equation 

 r' = 2g/i, and I thinkyou will see why kinetic energy = ^mr'. — X. Y. 

 Yes ; we do think it impei-tinent curiosity to inquire into a man's 

 religious belief, while we consider it only just and proper to inquire 

 how he discharges duties for which he is paid (by you and me, 

 among the rest). If men thus paid are hardened against deserved 

 censure, they must be punished in any way by which they can be 

 reached — by ridicule, if that serves. As for courtesy, a man 

 of sense who had found reason fail, would as soon think of 

 extending courtesv to — well, to anv other wilful wrongdoer. 



©ur esabidt Column. 



By " Five op Cldbs." 



PLAY FOURTH HAND. 



THE fourth player's duty is usually but to -win the trick if he 

 can, and as cheaply as he can. The exceptions usually belong 

 to the cases in which the general conduct of the hand involves 

 considerations overruling such rules of detail as we are for the 

 present considering. Thus, the player fourth in hand may bo 

 unable to win a trick except by ruffing, and ruffing may mean 

 giving up all chance of commanding the run of trumps and bringing 

 in a long suit : in that case, he would pass tho trick. Or it may 

 happen that the card of the suit with which he could alone take 

 the trick would obviously be likely to servo as a re-entering card, 

 after trumps were exhausted : in such a case, it the chances were 

 dearly in favour of that power of re-entry being obtainable in no 

 other way, fourth hand should pass the trick. The consideration of 

 such |K>int8 belongs to a later stage of our discussion of Whist 

 principles. We may simply note hero that in all such cases a good 

 general rule to bear in mind is that a certain trick ought not to bo 

 passed, unless there is a great probability of making two by so 

 doing, always remembering, liowevcr, that if the game con only bo 



