Feb. 9, 1883.] 



KNOWLEDGE • 



89 





" Let Knowledge grow from more to more." — Alfred Tennyson. 



Xrttrre to tl)r editor. 



Only a small proportion of Letters received can possibly he in- 

 serted. Correspondents must not be offended, therefore, should their 

 letter!, not appear. 



All Kditoriid communications shotild he addressed to the Editor of 

 Knowledge ; all Business communications to the PcBLisnERx, at the 

 Office, 74, Great Queen-street, W.C. If this is not attended to, 



DELAYS AKISE FOR WHICH THE EDITOR IS NOT EESPOXSIBLE. 



All R''miltances, Cheques, and Post Office Orders should he made 

 payable to Mes.srs. Wtman & Sons. 



The Editor is not responsible for the opinions of correspondents. 



No COMMrNICATIONS ARE ANSWERED BY POST, EVEN THOCGH STAMPED 

 AND DIRF-Cn:D ENVELOPE BE ENCLOSED. 



SUN-DIAL OF AHAZ. 



[702] — There is not the lenst necessity for snpposing Hezekiali's 



parhelion to have differed in position from the commonest sort, 



such as my Portsea ones, if wo snppose it rvt the same time of day, 



Ih. 30m., and in December or January. Botli accounts, indeed, 



almost necessitate that verj- time of day ; for they say that the 



shadow (or tlic sun, Isa) was " brought back ten degrees, by which 



it had gone down;" implying, if strictly taken, that this was the 



whole amount it had declined, or that the shadow came back just 



to the meridian. If the "degrees" then were fortieths of a 



quadrant (and forty occurs so constantly in the Old Testament 



as to be the likeliest number by far), the hour must have 



f been half-past one, the same at which our Portsea display 



> became overclouded, and the left-hand mock sun was due 



J, south. Having seen proof that the effects all ceased while the sun 



|kwas higher than about 37°. 1 vaguely inferred that in a low latitude 



Vthey would only be possible early or late in the day. Hut the mid- 



^winter sun at Jerusalem only reaches 35° on the meridian, about 5° 



I less than at Portsea on March 2!', so that foratleasta month before 



( and after midwinter the sign was possible at noon. 



These degrees, equal to nine of our minutes, must he the earliest 

 artificial time-measnres on record, as hours are said to be named by 

 no writer before Daniel, and were at first but three to the quadrant 

 thongh six are made, as now, in the eight dials on the Tower of the 

 Winds at Athens, and the old Greek dials in the British Sluseum. 



E. L. G. 

 [Several correspondents mistakingly suppose that " E. L. G.," in 

 explaining by what simple nafui-al means the shadow might go back, 

 proposed to dispute the occurrence of anything miraculous. It 

 should be obvious from his lirst letter that this is not the case. Of 

 conrse, if the event happened as described it was miraculous, what- 

 ever the explanat ion. Equally of course, many will prefer to believe 

 that -while sneh a phenomenon was witnessed in Hezekiah's time, 

 it was only long after that the story assumed its present form, 

 according to which the going back of the shadow was promised 

 lieforehand. — K. P.] 



WEARING STAYS. 



[703]— As the father of young daughters who, like knowledge, 

 are " growing from more to more," I have followed with great 

 interest the letters in Knowledge about corset wearing, and the 

 thought has occurred to me that perhaps you could suggest a 

 rational way of dressing girls. Their mother says that without 

 "stays" they will simply be " lumps." W. Watekholsk. 



[The discussion of this subject began with the advocacy of 

 tight-lacing. The question is one of extreme importance — of vital 

 importance. A writer says " Men are not interested in it"; but men 

 (of sense, hien entendu) are very much interested in it. I have 

 myself no suggestions to offer, simply because I regard the matter 

 as one for women to deal with. The wife of the just-mentioned 

 writer says she "will wear stays" (presumably tightly-laced 

 ones), and he says "she is quite right." But, putting mere 

 chaff of that sort on one side, I can onlynote that quite a large 

 number of ladies, whose experience of the " Rational Dross" system 



has reached me, speak of it as much warmer, much lighter, much 

 better-looking, for women who by nature have wai.-^ts — but I fear 

 it is open to the objection that a " bunchy " woman would look 

 worse in the "rational dress." Such is the verdict of the feminine 

 authorities whose opinion has reached me. — R. P.] 



WEATHER PREDICTIONS. 



[704] — An evening paper writes as follows: — "The authorities 

 of the Sleteorological Office have at length given uj) the weather in 

 despair. For many months they have been singularly unfortunate. 

 There was a time when it was otherwise. Personal observa- 

 tion of the daily forecasts led mo at one time to regard 

 them with wondering confidence, but for at least si.\ months 

 things have gone wrong, and it came to pass that the nearest 

 approach to a safe forecast of the weather was to count upon the 

 reverse of the prediction from the meteorological department. On 

 Sunday night the oflice gJive it up with something like a cry of 

 pathetic despair. They declared that a definite forecast was im- 

 l)Ossible, but very unsettled wet weather was likely to prevail 

 generally. This looked like treading on sure ground. A man who 

 at this season would predict wet weather as likely generally to 

 prevail could not be called rash ; but here again the hapless 

 iletoorologieal Office is ludicrously in the wrong; yesterday was, 

 for London, a phenomenally clear and sunlit day, and similar 

 wealher is rejiorted all through the southern districts." — London 

 Paper. 



Is it not time now that this farce is ended, and the money that 

 has been wasted annually upon this useless office be in future saved 

 to the revenue of this overtaxed country ? (i. 1. L. 



OUR FOREFATHERS. 

 [705] — Would yon kindly assist me out of a perplexity ? A short 

 time ago, I read in the Daily Telegraph that, according to calcula- 

 tions made by an Italian statist, every person now alive is entitled 

 to claim nearly one hundred and forty thousand billions of ancestors 

 by going no further hack than the year one of the Christian era. 

 taking three generations in a century, or about fifty-seven in all ; 

 basing the calculation on the fact that every person has, or has had, 

 a father and a mother, and again that father and mother had the 

 same progenitors, which were of necessity doubled with every gene- 

 ration as we go further back. Now, there is nothing to be said 

 airainst the correctness of this calculation, but then we come to the 

 astounding fact that such ,an enormous number of ancestors is 

 clained by a single person, whilst even now, after 1882 years have 

 elapsed, during which period the population has rather increased 

 than decreased, there are only about one thousand millions of 

 people alive. But this is not all. Our ancestors living in the year 

 one had also fathers and mothers, and I can't see what can stop us 

 going further and further back for four thousand years more, when 

 we come to the time of the beginning of the world, when there were 

 actually only two people inexistence.[!] And mind, Mr. Editor, this 

 is the result of starting with only one person, whilst there are one 

 thousand millions besides who can make the same claim. Do you 

 wonder that I am perplexed H Please to help me to clear it up, and 

 oblige, A CON.STANT Uf.ader. 



[If a " Constant Reader" will consider the case of, say, twelve 

 married couples, starting a colony, in a place to which no others 

 ever come to stay, and carefully note the effect of natural increase 

 resulting from intermarriages among the descendants, ho will see 

 that if in a generatitjn the population dovibled— say three genera- 

 tions in a centurj- — then, in a thousand years, the population would 

 consist of some 26,000,000,000, all descended from twenty-four 

 persons. Yet each person would be theoretically descended from 

 2,150,000,000 ancestors, the number being made up by the varying 

 u-a'is in which each of the original twenty-four is related to each 

 of bis descendants in the thirtieth degree. When first-cousins 

 marr)', to take a simple e.tamplc, their children have only six 

 instead of eight great-grandparents ; but one great-grandfather is 

 (or may be) father's father's father, and mother's mother's father. 

 If two brothers marry two sisters, and a son by one marriage 

 marries a daughter by the other, the children ol this last marriage 

 have only four great-grandparents; but each of these is doubly a 

 great-grandparent. When a longer range of generations is taken, 

 these relationships not only may become, but do become, much 

 more complicated. Thus tlio chances are that any person casually 

 met in society is not only a cousin far removed, but a cousin in 

 various degrees of removal, a<^cording to the way in which cousin- 

 ship is estimated, and a cousin also in hundreds of different ways. 

 It is almost infinitely unlikely that, if all the relationships could be 

 traced back a hundred generations, no consinship would be found, 

 in the case even of a man in very different rank — much higher or 

 much lower. — R. P.] 



