•M'2 



KNOWLEDGE • 



[Al'Kll 



1882. 



I>ri(l;;<', aiul lui < ' liiul beaten in hollow fashion 



th(< Ain'Tiinii fi>iir li'iii lliiiMinl, it was only nutiiral that 

 Mr. Ski'v slicul.i I"- iticlii.ril to think th.- O.xf.iiii style- 

 niu.st )>(■ the lirttvr ; nnd so it iin<|Uf.stiunal>ly i.s ; 

 Jiut thi> st\l<' he (IcscrilM'K Ik that wliicli was, nnd is, 

 fMijoiiU'd rigidly l>y Canihridgi' cuptuins, and ohsiTvutiun 

 hhow.s that O.xford docs not follow that .styk-, liut 

 lirings tlio anns to work from tlu' lifginning. How ony 

 douht could <'vrr hr I'nti-rUiincd on this point l>y those who 

 l.niw how nnich farther hack than <).\for<l the Cainhridge 

 «j"ws have always swung, is ditlicultto understand. For, if 

 tin- arms arc .straight when the body reaches the vertical 

 position, the body nuist, of course, swing further Itack 

 while the arms do their work, as yet scarce begun ; but, if 

 <he arms have lieen nt work while the body is swinging to 

 uj>ri;;htne.ss, the arms have little left to do, and therefore 

 the body need swing back but a very little. As O.xford 

 men umiuestionably do 710/ swing far back, while Cambridge 

 •men do— even men who know nothing practically of rowing 

 ■can see Uiat — it should need no denionstration that O.xford 

 men do more of their arm-work than Caudiridge men during 

 the beginning of their stroke. " And I myself, with my 

 > ery own eves have seen," as the old chronicler wrote, that 

 O.xford men and London nu-n too, and watermen always, 

 row with body and arms, and legs too, from tin' very 

 •beginning of the stroke. 



Jlcanwhilc, at Cambiidge they (piietly accept the faith 

 that O.xford men swing back with rigid, unbent arms (and 

 they see this in tub practice and paddling, where it is the 

 correct thing to do) ; so tliey keep to the rule, unconscious 

 or forgetful that it is the old rule, good only for the old 

 style of boats ; and so they get beaten, unless they have 

 overwhelming superiority of strength, when they win by 

 lialf a length or a length, where O.xford, with the same 

 superiority of strength, would have won by half-a-dozen or 

 a dozen lengths. 



I write confidently, but I write when there is good 

 prospect that the matter will be tested in a way there can 

 be no mistaking (1 would stake a good deal on the result 

 if I were a betting man). Mr. Muybridge's method of 

 instantaneous photography, which has shown how a horse 

 gallops and liow an athlete tvirns a somersa\dt, will very 

 readily show how an Oxford or a Cambridge oarsman rows, 

 and is very likely soon to be applied to the work. But 

 there is a practical test which Cambridge captains might 

 very easily try, and perl.iaps apply the result in a way very- 

 pleasing to themselves and their crews. Let a crow, each 

 uieml)er of which rows well the Cambridge dragging swing- 

 back, go over a measured distance, say half-a-mile, at their 

 l)est speed in that style, and then let them —though, per- 

 haps, a little tired— go back to the starting-place and go 

 over the course again with a changed style. Let stroke 

 and each man of the crew agree for awhile to give up their 

 cherished drag and lightningfeather ; let the arms be sturdily 

 called into action, in due subordination, of course, to body 

 and in due alliance with the leg.s, from the very beginning of 

 the stroke, so that when the body comes upright, the arms 

 have nearly done their work. Let not the stroke be 

 hurried, but a steady (not sluggish) recovery, precede the 

 simultaneous grip at the beginning. I will undertake to 

 say that, even at the first trial (absolutely important 

 though practice is in this .style, where everything depends 

 on the work being done at the same time), even at the 

 first trial, I sa}-, the result will be such as to show unmis- 

 takably how nnich more etlective, and also how much 

 easier, this style is than the style inculcated forty years ago 

 for I)oats as dillerent from those of our time as a barge 

 from a pleasure-boat, or a pleasure-boat (with a party of 

 ten under her awning) from the old clinker built racing craft. 



AT 



THK KF.ECTRICAL EXHIBITION 

 THE CRYSTAL PALACE. 



ElfMITII NOTICK. 



J'l' is not ilitlii'ult to understand that if a certain amount 

 of electric energy is recjuired to render a carl>on fila- 

 ment I in.- long incandescent, ten times that eniTgj- will \>e 

 reijuired (presuming there is no other resi.stance in the 

 circuity to similarly heat a filament 10 in. long. If, how- 

 ever, we have sullicient energy to heat 10 in. of carWn, 

 it matters little whether that carbon is in one piece or 

 in ten, or in any number of pieces making up the same 

 total length. Here, then, is the first i)rinciple in the .so- 

 called division of the electric light. The great object to be 

 achieved is really a dislribulion of the light, necessitatetl 

 b)' the great diminution of luminosity as we recede from 

 the source of light. The exact falling-off is "inversely as 

 the Sfiuare of tin? di.stance," that is to say, if we have a 

 luminosity e(|ual to twenty candles at a distance of 1 ft., 

 tlie intensity at - ft. will be — 



2' : l'::20: r 

 or 1 : 1 ::20 : 5 



•')-candIe power will, therefore, be the luminosity at 2 ft 

 distance. This explains how it is that a large light is so 

 expensive, or lacks economy so much, when compared with 

 a number of small lights placed at the proper distance from 

 each other to illuminate the same area. 



Fig. 1 illustrates the method of connecting the lamps, 

 known as "joining in series " — that is to say, the whole of 

 the current passes through each lamp in succession. 



Fig. 2 illustrates another method of joining up, and is 

 known as the " multiple arc," or " quantity " arrangement. 

 The current comes in from the machine at +, and retui'ns 

 liy the other wire marked — . In this case the current, instead 

 of passing through each lamp in succession and haring 

 to overcome the added resistance of, say four lamps, is 

 assisted by their conductivity, and divitles itself bet^vecn 

 them, the resistance being thereby considerably reduced, 

 just as a Mow of water which requires a certain pressure 

 to push it through, say, four yards of pipe, requires one- 

 fourth of that force to drive it through one yard. If we 

 were to place four pipes, one yard long, side by side, the 

 required pressure would be again quartered. .^^ctually, 

 therefore (assuming each lamp to ofter 50 ohms' resistance), 

 joining in series would give 200 ohms for four laups, while 

 in multiple arc the resistance would be reduced to '2 5 ohms. 



But suppose again that in the single pipe thf quantity 

 of water was only sufficient to fill one pipe, we siould have 

 to quadruple the supply of water in order to fil four pipes 

 placed side by side. Accordingly, the currmt required 

 for the arrangement described is of less intoisity, but of 

 greater volume, to produce equal degrees of hminosity. 



Fig. 3 is another arrangement known as * mixed," that 

 is, a combination of series and quantity. The diagram 

 may be left to explain itself. 



We should have liked this week to give, in continuation 

 of our remarks on incandescent lightinji a few mathe- 

 matical details concerning the arrangemoit of the lamps 

 and generators. These details, however, will be best 

 comprehended after we have finished nir description, in 



