September 1, 1887.] 



♦ KNO^A^LEDGE ♦ 



257 



Such pieces of luck are not commoa even in a lifetime. 

 Yet I consider myself even more exceptionally lucky in 

 that my business took me to America in 1873-7i, when the 

 Tichborne trial was in progress, filling three-fourths of the 

 space in our English newspapers, occupying nine tenths of 

 men's talk and attention. 



* * * 



I HAVE been luckier yet in that throughout all this 

 Jubilee business I have been where the distant hum of it 

 all scarce even reached men's ears. 



* * * 



In these days no man can be an Admirable Crichton — 

 assuming the actual Crichton was really so well informed 

 in all the science of his day as men said. But if any man 

 has a chance of taking even a bird's-eye view of the science 

 of our time, or of its history during, say, the past half- 

 century, it can only be a man who is thoroughly grounded 

 in mathematics. The effect of trusting even the sketching 

 of general science to men who are not mathematicians, 

 however eminent they may be in special departments of 

 research, must ever be disastrous. Of this truth the last 

 few months have afforded more than one " awful example." 



It should be obvious, of course, that no man can appre- 

 ciate the work done in our time in physics, astronomy, 

 mechanics, and kindred departments of science, without 

 being well versed in the general principles of mathematics. 

 But, as Galton well pointed out when, in dealing with a 

 subject seemingly biological, he found mathematical formula3 

 essential to successful inquiry, mathematics is " queen of the 

 whole domain of science." 



* * * 



Apart from the direct application of mathematics in 

 nearly every department of science, the mathematical turn 

 of mind is of important service even where no mathematics 

 may be employed or required. To recogni.se the truth of 

 this, one need only notice the failures which men not 

 mathematically trained to close reasoning, nor by nature 

 gifted with mathematical potentiality, almost invariably 

 make in scientific researches of any difficulty. I know of no 

 example of a continuous series of investigations, logically 

 pursued to final success, by any man not mathematically 

 minded. Darwin, Tyndall, and Spencer, who have done no 

 independent mathematical work, have been pre-eminently 

 mathematical in their manner of working and thinking. 

 And some even who have objected to the too purely 

 mathematical treatment of theii- special subjects have 

 shown clearly that, had they not been great in such special 

 work, they might have been eminent in mathematics. 



* * * 



I HAVE been asked by a correspondent in America what 

 are " the curious phenomena of the instantaneous reversal 

 of comets' tails on passing their perihelion," refeiTcd to in a 

 recent article on the progress of science. I really am 

 unable to say. A comet's tail is directed along the major 

 axis of the orbit when the comet is in perihelion, and does 

 not point in the reversed direction unless when the comet is 

 in aphelion, when, however, a comet usually has no tail. I 

 have never heard of the instantaneous reversal of a comet's 

 tail either at or near perihelion. The only cases of quick 

 reversal occur where a comet's perihelion is very near the 

 sun, when it has happened (in perhaps half a dozen cases 

 out of hundreds) that, in the course of a few hours, a comet's 

 tail has been actually reversed, as the comet's head has 

 passed, in that short time, from a position on one side of the 

 sun to a position on the side exactly opposite. But the 

 reversal does not take place at perihelion, but as the comet 



passes from one end to the other of the htics rectum of its 

 orbit — a line at ri'jht amjles to its direction from the sun 

 when in perihelion. Nor is the reversal ever instantaneous. 

 In the case of the great comet of 1811 the reversal was not 

 completed in much less than a year. There is no other 

 mystery in such reversal, whether slow or rapid, than there 

 is in the general law that a comet's tail is turned always 

 from the sun, of which the.se reversals are but special cases. 



* * * 



A CORRESPONDENT at Pemambuco asks me (or rather, I 

 should say, asked me a long, long time ago) whether the 

 right saying is " De morluk nil nisi honum," or " De 7nortuis 

 nil nisi bene." I never had any classical knowledge worth 

 speaking of, though I read my Homer, my Virgil, and my 

 Horace, my Euripides and my Terence, with ever-growing 

 pleasure and satisfxction — which, I find, is not always the 

 case with those painstaking college friends of mine who 

 could descant most learnedly on the force of Kara in com- 

 position, and like delectable details. Frankly, I have not 

 the slightest idea where the expression which in England 

 we render always de mortuis nil nisi homim had its origin. 

 If such origin is known, the question of the right form can 

 probablj' be at once disposed of Yet, after all, even this is 

 doubtful. Every one knows that Virgil (or Vergil — which 

 is it?) wrote Facilis defCfnsus Averni or Averno ; yet no 

 one would pretend to aver that Averni or Averno is right, 

 in ftice of the fact that while many excellent editions give 

 one form, many not less excellent give the other — the old 

 Delphin and the modern Oxford agreeing in Averno, which 

 is the form I always employ myself. 



* * * 



INIy Pemambuco correspondent, who is a naval officer 

 (and whom I beg to thank for a highly interesting letter) 

 writes that every German at his station gave bene as the 

 right reading, every Englishman giving honum. A German 

 paper which was referred to on the subject thanked its 

 correspondents for their trust in its Latinity, and explained 

 that since the expression De mortuis nil nisi hon}im, or bene, 

 is short for De mortuis nil nisi bonum vel bene dicitur, or 

 " Let nothing be said of the dead but," &c., bene the adverb 

 must be preferable to bonum the adjective. To one who has 

 no pretensions to Latinity, dicitur, as used by thLs classical 

 authority, sounds appalling. In my ignorance 1 should 

 have suggested dicatur. But be that as it may, I cannot 

 but think his dogmatic decision open to question. In read- 

 ing dear old Cicero I have come across the suggestion 

 Ul niltil pro'ter verum diceretur bonum ; and Latin good 

 enough for Cicero is good enough for me, however unsatis- 

 factory it may seem to our classical German editor. 



* * * 



Of course all English readers remember Thackeray's 

 Roundabout Paper " Nil Nisi Bonum," which settles the 

 question of customary English usage. 



* * * 



Speaking of familiar Latin sayings and quotations, I 

 frequently notice in English, American, and Continental 

 papers the rendering (in their various vernaculars) "I fear 

 Greeks and those who biing gifts," as conveying the idea 

 expressed in the fomiliar " Timeo Danaos et dona ferentes." 

 Laocoon, we may be sure, addressed no such feeble warning 

 to his countrymen, when he closed his ardent address with 

 the familiar words : — 



Equo ne credite, Teucri. 

 Qiiidquid id est, timeo Danaos et dona ferentes. 



Scan the line, and the stress falling on the et, as it closes 

 the heavy spondee before dona ferentes, would of itself 

 suffice to show that it means not merely " and," which in 



