342 



• KNOWLEDGE • 



[Fbb. 17, 188: 



by saying that it is almost alisurdly cuutious. I ]iiiiiit 

 out tlint if there are ]iluncts circling around the sun which 

 bla/.od out in C'oronn in May, 18GG, to eight hundred times 

 its former lustre, and if there were living creatures on 

 them at all resembling ourselves, those creatures must 

 most i-ertaiidy have l)een destniyed. It takes no wizard to 

 know this. I tlien go on to suy that " if at any time a 

 great comet falling directly upon the sun " (which the 

 comet of 1813 and 1880 most certainly will ncrer do) 

 " should, by the swift rusli of its meteoric components, 

 excite the frame of the sun to a lustre far exceeding that 

 with which he at pi-eseut shines, the sudden access of 

 lustre and of heat would prove destructive to every 

 living creature, or, at any rate, to all the higher forms 

 of life, upon this earth." Ajid though 1 knew when I 

 wrote this that 1 was making no rash j)rediction, I protest 

 I never noticed until the rash predictions assigned to mo 

 by the Spectator and the Bishop of ^lanchester set me 

 reading over my own essay, that this amounted only to an 

 announcement of the following highly-impressive nature : — 

 If such a comet as we have no reason to suppose actually 

 existent (nay, every reason to consider cei-tainly non- 

 existent in the sun's case), should produce a degree of 

 solar heat (which such a comet may, or may not, be 

 capable of producing), exceeding hundreds of times tlu- 

 sun's present heat, and if that heat lasted but a few days, 

 the earth's inhabitants must all perish. This very cautious 

 announcement does not mean, I venture to point out, that 

 fifteen years hence the comet of 1843 falling into the sun 

 will so raise his heat that all of us will be destroyed. 



I may remark that the newspaper announcement has 

 elicited various expressions of opinion, showing the great 

 ignorance which prevails even in these days of cheap scien- 

 tilic literature respecting scientific matters. Thus it has 

 been carefully explained by some that comets are entirely 

 vaporous, evidently in ignorance of what has been learned 

 respecting the meteoric nature of comets ; by other writers, 

 that Lexell's comet was absorbed by Jupiter or by his 

 satellites (which Leverrier entirely disproved) ; while 

 another writer (in the C/irisliaii World, and followed by 

 the Globe) propounds the amazing statement that the sun's 

 hi'at does not travel so quickly as his light, so that even 

 though vfe saw a great outburst, due to the destruction of 

 a comet, some ninety or a hundred years would have to 

 pass before the earth would receive the heat then gene- 

 rated ! It would be interesting to ascertain whence this 

 singular idea was ol>tained — by what strange misapprehen- 

 sions of some statement in a scientific work. Of course, 

 there is not the slightest foundation for it. The sun's heat 

 comes to us with his light, not only travelling at the same 

 rate, but being a part of the \ cry same undulatory disturb- 

 ance, and a considerable portion being derived from the 

 very same waves. Some of the waves, indeed, which aflect 

 us as light affect us very little as heat, and some of the 

 ■waves which affect us as heat, jiroduce no ertect which 

 the eye can appreciate as light. But the orange and red 

 light-waves are very active as heat-waves too, and there is 

 not the slightest reason for supposing that the so-called 

 dark heat-waves, which, with these, make up tlie total 

 supply of solar heat, would lag many seconds behind them 

 on the journey earthwards. 



However, there is not the slightest reason to fear that 

 the comet of 1843 and 1880 (assuming they are the same) 

 will do any harm to the solar system when finally absorbed. 

 It would be quite otherwise, I believe, if such a comet as 

 that of the year ISll, Fig. 3, were to fall directly upon 

 the sun. This, the most remarkable (in reality, though 

 not in appearance) of all known comets (see Kxowlf.dge, 

 No. 5, p. 8G), was fortunately some 100 million miles from 



tlie sun at the time of it« nearest approach to him, and can 

 never liring the slightest trouble to the solar system. But 

 if its course had chanced to be directed full upon the sun, 

 the meteoric ma.s.se3 doubtless forming its liead and train 

 (not tail), falling in countless millions upon him at the rate 

 of more than 300 miles per second, when they crossed his 

 visible surface, and jirobably passing tleep below that 

 surface with ever and most rapidly-increasing velocity to 

 reach his real nucleus, would ha\e generated an intensity 

 of heat far exceeding that which he constantly emits. The 

 incrca.sed emission might not ha\e lasted a mouth, or even 

 a week, but it would have sufficed. 



So, again, what we now know of conietic structure leads 

 us to believe that the comet of 1858, called Donati's, whose 

 head is shown in Fig. 2, would have proved a very 

 dangerous visitor had its course led it directly towards the 

 nucleus of the sun. Fortunately, the chance of any comet 

 visiting our system from interstellar space, travelling 

 directly towards the sun, is so small, that it may be 

 reckoned " almost at naked nothing." As to comets 

 already belonging to our system, if any such liave orbits 

 passing very close to the sun, so as to be checked in their 

 career at every perihelion passage, it is clear (from the 

 continuance of life during many hundreds of thousands of 

 past years on the earth) that the mischief must long since 

 have been taken out of them — unless we suppose (which is 

 incredible) that the last perihelion passage of such a 

 comet preceded the beginning of life on the earth. 



THE EFFECTS OF TOBACCO. 



By Dr. Mem Howie. 



PART II. 



IN the present day, wo can calculate vrith precision i. i^^ liiitt 

 time, to a nmiute fraction of a second, wliicli is recjuired to 

 transmit a message from the brain to the hand or any other portion 

 of the body ; and it has been distinctly shown that it takes mncb 

 longer to send such a message after the person experimented upon has 

 taken even a small dose of a narcotic. A message which could be 

 sent in OlOOJof a second, required 0'2970 of a second for its perform- 

 ance after two glasses of hock had been administered to the subject 

 of e-tperinient, thus showing how much even a slight narcotic in-' 

 terferes with the rital action of nervous tissue. The same effect is 

 produced by tobacco. Tobacco prevents waste of tissue, and thns 

 enables a man who smokes to live on loss food. This is con- 

 sidered a very strong argument in favour of the pipe; and 

 if good food could not be obtained, it might have very great 

 force. But plain, wholesome diet is cheap and easily proeared. 

 Moreover, " waste of tissue" is an expression which conveys an 

 utterly false imiiression. There is no such thing as waste of tissue, 

 unless the body is wearing away more rapidly than new substance 

 can be reproduced, as in certain fevers, consumption, ic. Tho ' 

 tissues of the body arc not a fixed quantity, like the framework of 

 a steam-engine ; they are ever changing, the old wearing away 

 to be replaced by the new. Life is a constant series of changesj 

 and the healtliier the man the more rapid, within certain Umito, 

 will be his change of tissue. You can only preserve the tissue of a 

 healthy man by lowering his vitality; the tissues thus preserved 

 cannot bear tho strain which can be borne by those of recent 

 manufacture, and thus the workiag power is diminished. An em- 

 ployer of labour in Liverpool, anxious for the elevation of his 

 workmen, suggested that they might with advantage give up the 

 use of beer and tobacco. They informed him, however, that in such 

 a contingency their wages would not support them, so great would 

 be their increase of appetite. But there is another side to this 

 (ju St ion, and it is, that such men would be able to do more work, 

 and conse((uently earn larger wages, by discontinuing the narcotic. 

 Men of all classes are very slow to learn that sound bodily health 

 is the best possible investment. The human machine is very easily 

 kept in order, but onco let it get out of repair, and it is mo6t 

 diliicult to set right. And it can only be kept in thorough repair 

 when every joint, muscle, and nerve is maintained in a condition of 

 persistent activity. I do not mean that a man should always 

 be engaged in exercising his various tissues and orgjins in order 

 to preserve health ; but 1 do n\aintain that every tissue should bo 

 80 actively exercised that it will be compelled to employ its entire 



