342 



KNOWLEDGE ♦ 



[Oct. -20, 1882. 



Thus the mean distAuco of the comet during its last 

 ciri-uit was no less than ITt'.iS 10,000 luilcs, its greatest 

 distance nearly twice this, or, roughly, about 357,000,000 

 u]ile& 



The velocity in perihelion corresponding to this mean 

 distance is less than tlic velocity per second with which the 

 comet first reached perihelion, by 



J^(3-.-J)orbv 3'V;00^j,^ 

 71,:>36 ^ • 143,072 



This is about a quarter of a mile or more, exactly 410 yards 

 per sei-ond, a reduction of velocity much more important 

 than either of the former two, but still small enough 

 compared with the velocity actually possessed by the comet 

 in perihelion. The actual reduction from that at the j)re- 

 itnling perihelion passage is (410 — 78), or 332 yards. 



A still larger reduction in tlie velocity at perihelion 

 would be recjuired to reduce the period from two j-ears 

 eight months, to one year. For with the latter period 

 the reduction of velocity in perihelion from that due to 

 motion in a parabolic orbit would be 



5(352) ++ , ., , 



4x930°'" 93 of. a mile per second. 



This is about 833 yards per second, or a reduction from 

 the velocity at the preceding perihelion passage by 



833 — 332 = .")01 yards per second. 

 There is reason to l>elieve that a more important reduction 

 than tliis took place — in which case the comet will be back 

 in less than a year. 



SCIEXCK OF 77/ A' TIMES. 



SCIENTIFIC articles in 7'A.- Tlmrs ar.' generally worth 

 reading, for the same reason that the Spartan helots, 

 when disguised in liquor, were worth watching — to wit, as 

 awful examples. But there arc degrees, even in such cases 

 as these. Under what conditions, we wonder, can the 

 following sentences from an article on earthquakes have 

 be<'n written ^ — " When the earth was conceived to be a 

 crust tloatint; on a sea of liquid fire, observation alone, and 

 not experiment, seemed applicable to the storms which 

 tossed and blasted the superincumbent mass. The ocean 

 of molten lava resembled a capricious monster, which obeyed 

 impulses incomprehensible to the sufferers by its fretful 

 furj-. An earthquake, according to the more recent belief, 

 which Mr. Mallets reasonings and illustrations have raised 

 to the level of a law, is but a variety, gigantic in its pro- 

 portions, of a process always in operation, and among the 

 regular machinery for the action of nature." [Did any- 

 one ever read such Knglish '(] "The earth is perpetually 

 br<-athing and sighing throughout its whole frame. Its 

 throbs cause a succession of minute motions as pene- 

 trating as the laltours of earth-worms, and as effective. 

 Sfjniewhere a1>out the stupendous mass a similar species of 

 movement is ever manifesting itself with a larger volume 

 in the form of oscillations. .... As Professor Milne 

 remarks, in the origin of the aj>tonisliing ebullitions called 

 earthquakes principal are usually modified by secondary 

 causes. .... The object of Professor Milne's lett<;r is to 

 urge the claims of seismology tc> fuller recognition in 

 countries tc/iicA n^it/icr can boagl nor have causa to 

 drrml thf. iMTlhtiuakes of the J'acific. Phenomena, he 

 point* out, are present in unfailing and unvarying 

 abundance within thes*- more t^-niperate regions. They 

 wait or they c<imc l<ack to Ix; inspected with a fjatience 

 and a rffgularity unknown in the resorts of earthquakes. 

 Modem s<.'ience has no inclination to toleratr; that the earth 

 should Vje suffering incessant modifications without inquiring 



what they are and how they are accomplished. Nature 

 and its acts and faculties have too complete an unity for 

 science to possess any option of neglect were it disposed 

 to be neglectful. 'J'he mieroseinmic motions and the oscil- 

 Uuions to which Mr. J/ilne ri'/ern, {f they are jmrt of the 

 ordinarij economy of nature, must mi.c with and all'ect all the 

 rest of' its departments. Even/or the purposes of experiment, 

 it is ilnpossilile to ' Iniry' or ' eat them up.' The sole remedy 

 is to consult them. The field has as yet few explorers. Its 

 conditions of exploration and the attainable results are 

 hypothetical. An extraordinary assemblage of phenomena 

 is sure to reward the eaily pioneers, lliey have a new 

 world before them. But nature, the more multiform its 

 energy and manner of working, shows itself only the more; 

 uniform at heart. Its laws are as simple as their agencies 

 are complex. Science dissipates mysteries at the moment of 

 (/rasping them. When the recesses of the earth are probe/ 

 thry will lie found to hide -no dark secrets defying tests and 

 (trraiigeiiii nts. The same analysis which promises to re- 

 duce earth tremors to a system, and display by what 

 physical instruments they are produced, may supply a clue 

 to the portent of an earthquake, yulure is as impatient (f 

 mdiislrosilies as sciei.ce. ]Vhen nature and science are 

 hthonring together apparent physical anomalies are very 

 speedily smoothed out and effaced." 



Comment on inanities such as these would be idle. We 

 have italicised the most salient absurdities, but there is 

 little to choose between these and the others, or between 

 the passages we have quoted and the rest of this scientific 

 " leadc^r." If these are ourjeaders, heaven help the led. 

 Yet many wonder that " the general reader " is not 

 attracted by science. How should he be when it is pre- 

 sented in such garb as this 1 



A HINT TO BOTANISTS: 



OR LEAF COPYING. 



IN reading the interesting account on the method of 

 taking the impression of butterflies' wings, which 1 

 have often myself practised, I recalled a very simple, 

 though excellent, plan for taking the impression of leaves 

 and flowers which I think is not generally known, and 

 which I intend to describe so that our entomologica? 

 friends may not have all the advantage over our botanical 

 scientists. In the first place procure a small bottle of oil 

 (I always use olive), a camel'shair brush or piece of rag, 

 half-a-dozen sheets of white unruled copying paper, and a 

 few sheets of white notepaper, also a good old-fashioned 

 tallow candle with a large wick ; having placed these 

 articles ready to hand, commence operations by taking the 

 leaves you wish to perform upon and putting them undei- 

 a press, if you possess or.e, or put them in a largo book so 

 as to get them with a fairly even surface ; then take a 

 large sheet of your copying paper and oil it completely by 

 rubbing it with your rag, taking care not to put on more 

 oil than is necessary ; this oiled paper must then be 

 placed in a good draught or in the open air till it 

 is fairly dr}'* (as otherwise the impression will be 

 faint). When it is ready, light jour homely tallow, 

 and taking the corners of your oiled paper, hold it over 

 the candle so that the flame just touches it, moving it 

 about to prevent it from scorching. Do this until a fine 

 layer of carbon is deposited on the paper, tliick enough to 

 only just see the light of the candle through the paper as 



• Yon can, of course, filwnyB keep some roudy, an it tukoH nljout 

 two or tbrco hourg to got moderately dry. 



