ni2 



KNOWLEDGE 



[Fkii. 10, 1882. 



the contmr)', so far as I produce any effect at all on tlic 

 drauj^lit, I must diminish it. For the draught dopoiids in 

 till' iiiuii\ (111 till- diminished density of the warmed air in tiie 

 nei;.;lilioiirho(id of tlie lire, and the cohl metal must t^i some 

 dr';;;ree iiicira.se the density of this air by cooling it. The 

 eflect may l>o very slight, but, sucli a.s it is, it in unfavour- 

 alijf. Hut liere is a correspondent who t<'lls me that 

 whether theoretically the poker should make the fire burn 

 up or not, as a matter of fact it dues. Kepeiit<-dly he ha.s 

 tried the experiment, and after exhausting in vain every 

 art he possessed to make the lii-e burn up, he found tlie 

 poker put across the top bar, immediately, or almost 

 immediately, produce the desired result. Science is bound 

 til listen to evidence of this kind, for science deals with 

 phenomena, and even when jihenomena seem to point to 

 something which appears utterly incredible, science has to 

 iiKjuire into tlie matter. Well, in this ca.se, what are the 

 facts 1 Someone tells us that he lias repeatedly tried in 

 y.iin to make a fire burn up, but when he put the poker 

 across it, the fire presently became clear and bright. 

 Multitudes of contrary cases might no doubt be cited, but 

 let us suppose that none could. Are we therefore to infer 

 that in these cases the poker drew the fire up t A new- 

 law of nature would be indicated, if this were so ; and a 

 new law of nature is worth learning. But when due 

 inquiry is made, it appears that there is no such law — as, 

 unfortunately, we might have expected. Our correspon- 

 dent, who found that when he jmt the poker across the tire 

 it drew up, is unquestionably but an unskilful fireman. He 

 puts on coals, and jiokes and stirs the fire, unconscious of 

 the fact that this is just the way to put a fire out. When 

 the fire is all Viut hopelessly reduced by liis unskilful 

 mcjisures, he puts the poker across the top bar. According 

 to old-fashioned superstitions, he makes the sign of the 

 cross across the fire-place, and the fire, in wliich until now 

 there seemed to have been some evil spirit (that is what 

 people mean when they say " the devil's in the fire "), 

 is purified from the unclean presence and begins to burn 

 up. That would have been the old-fashioned interpretation 

 of the change; unfortunately, science takes another view of 

 the matter. It sees reason to believe that the change took 

 jjlace simply because the disturbance to which the fire had 

 before been exposed was bad for it. Putting the poker 

 across the top bar meant letting the fire alone, and giving 

 it a chance to burn up. 



Singularly enough, I had occasion, when the last 

 S"ntence was just finished, to leave my study. When I 

 came back, an hour later, I found that my tire, which in 

 the meantime must very nearly have gone out, had been 

 recoaled — and the houstiinaid, or whoever had attended to 

 it, had, after the fashion of her tribe, put the poker across 

 the top bar. The fire was not burning very brightly — on 

 the contrary, it sciemed inclined to go out. Yet, rashly 

 daring, I put the poker down — from scientific principles I 

 (ibject to seeing bright metal smoked and dulled — and went 

 on with my work, intending, if the fire went out, to call 

 Mimcone in to light it again. However, it so chanced that 

 lifter the poker was put down, the fire began to burn 

 jiretty brightly, and as I write there is every promise of a 

 good fire. Am I to infer that taking the poker from across 

 the top bar made thi^ fire burn up? Of course, the real fact 

 was, that when the tire .seemed dull it was really making 

 steady progress, and whether [ had taken down the poker, 

 or supplemented its salutary action by putting another 

 poker across tin- top bar, would have made not one particle 

 of difference. 



That our domestic servants should consider the poker 

 aii-oss tlie top bar a specific for making a dull fire burn up 

 is vi-ry natural. Their manner of treating fires is un- 



scientific ill the extreme. A Cambridge Fellow, wlio ki.- .^ 

 very little about the fair sex, except what he might gather 

 from the ways of "bed-makers" and his recollections, 

 perhaps, of doiuestic servants at home, used to define woman 

 as " an inferior animal, not understanding logic, and poking 

 a fire from the top." Most servants do this. They also 

 have two utterly erroneous ideas about making up a low 

 fire — first, that tlie more fuel is jiut on the better; 

 secondly, that after putting coal on it is desirable to stir 

 the fire. As a matter of fact, when a tire is low, the 

 addition of fuel will often put it out altogether, and the 

 addition of much fuel is almost certain to do so ; and in 

 (;verj- case the time to stir the fire (when low) is before 

 coals are put on, not after. Generally it is well, when a 

 fire is low, to stir it deftlj', so as to bring together the well- 

 burning ]iart.s, and then to wait a little, till they begin to 

 glow more brightly ; then a few coals may be put on, and 

 after awhile the fire may again be stirred and some more 

 coals put on it. When a low- tire has been unwisely treated by 

 being coaled too freely, and the fresh fuel uselessly stirred, 

 it is generally the case that the only chance for the fire is 

 leaving it alone. Susan does this when she puts the poker 

 across the top bar, and unconsciously she retains the old 

 superstition that by thus making the sign of the cross over 

 the fire, she sends away the e\il beings, sprites, or whatever 

 they may have been, which were extinguishing it 



That letting the sun shine on a tire puts it out is not, 

 like the other (in its real origin, at any rate), a superstition, 

 but simply an illusion. A correspondent writes that it is 

 believed in by nine persons out of ten'^ but in this it is 

 like all other wrong beliefs. Scientitic methods of inquiry 

 and reasoning arc followed by fewer than ten in a hundred ; 

 and although nowadays the views of science are accepted 

 more widely than in olden times, this is simply because 

 science has shown its power by material conquests. 



I do not think that my friend Professor Tomlinson's 

 experiments on the burning of candles in sunlight and in 

 the dark would be regarded by all as decisively showing 

 that sunlight does not interfere with combustion, though, 

 rightly apprehended, they go near to prove this. But d 

 priori considerations show conclusively that though by 

 warming the air around a fire the sun's rays may, in some 

 slight degree (after a considerable time), affect the progress 

 of combustion, they cannot possibly put the tire out in the 

 sense in which they are commonly supposed to do so ; in 

 fact, a fire would probably burn somewhat longer in a room 

 well warmed by a summer sun than in a room from which 

 the solar rays were excluded. (The difTerence would V>e 

 very slight.) 



NIGHTS WITH A THREE-I^'CH 

 TELESCOPE. 



By "A Fellow of tuu Royal AsTiiosoMnj.\L Society." 



r|"^0-NIUnT we will avail ourselves of the /Zodiacal Map, 

 .1 oil p. 22.'">, and examine some of the objects it con- 

 tains ^vhich have not yet been described in these papers. 

 Before commencing our stellar work, though, wc will have 

 a look at ISIars, now travelling quickly away from us. He 

 is apparently becoming rapidly smaller, as lie is receding 

 from the earth, and a good deal of the detail which would 

 have been visible in the instrument we are employing at the 

 end of last December, has now become imperceptible. 

 With a power of ISO or upwai-ds, though, the planet at 

 iiioiiients of the best definition will be seen as in Fig. 17. 



What is technically called the gibbous appearance of 

 Mars will at once strike the observer's eye. In other 



