♦ KNOWLEDGE ♦ 



[Oct. 13, 1882. 



i- iM'. " Rowing," says Maclaren, " gives employment to a 

 jKirtion of the buck, more to the loins and liips, and most 

 of all to the legs, but it gives little to the arms, and that 

 little chiefly to the forearm ; and least of all to the cliest" 

 He was speaking, however, of rowing in light racing-boats. 

 In ordinary river-boats, the forearms get a good share of 

 work, and the dorsal muscles probably get more work than 

 the legSL As for the chest, it gets so little work that it 

 seems, in the case of many persons who devote a great deal 

 of their time to rowing, actually to shrink. 



We cannot direct attention too strongly to what Jlac- 

 laren has said on this point, because what he says is true 

 of every kind of rowing, from pulling a heavy, " inrigged 

 tub," to rowing in the lightest outrigged craft which has 

 ever yet been constructed. " The pari of the body vhich 

 receives tlu smallfM nhare of the exercine in rou-ing is thf. 

 efiest" he says ; " it has little or no employment in the 

 muscular eflbrt required for the propulsion of the boat; 

 and this i» impresgively exident in the results. Xot only 

 does the thest mnke no advance in devrlopmenl in this exer- 

 cise, but if it be exclusirely practised, an absolutely de- 

 pressing effect is jtroduced." No single result of recreative 

 or systematical exercise may be more fully substantiated 

 than this. Take any crew in the University, just as it 

 stands, and at any stage of its practice, and it is 

 possible, in a given space of time, by varied sys- 

 tcmatised exercise, to increase the chest of every 

 man by a given number of inches, with a propor- 

 tionate development of power ; let this cease, and ex- 

 clusive rowing exercise be resumed, and the progressive 

 development of the chest will also cease ; nay, its muscles 

 will lose their condition, and their power will decline, in 

 obedience to the organic law that power is in relation to 

 employment, for here they have virtually none. I could at 

 this moment point to men who have had rowing for ex- 

 clusive exercise since they came to the University, — men 

 endowed with an organisation capable of the finest develop- 

 ment, whose chests have been almost stationary for years, 

 the years during which they should liave made the greatest 

 advancenient — who have now, in fact, the same develop- 

 ment in this region which they brought from school, lin- 

 gering at thirty-six or thirty-.seven inches, when forty or 

 forty-one was fairly within their reach. 



Wo shall illustrate our next article with two pictures, 

 one from a photograph of a successful oarsman, the other 

 showing what properly-proportioned chest, arms, and 

 fchoulders should be like, 



{To be continued.) 



SECOXDARY BATTERIES OR 

 ACCUMULATORS. 



ONE of the greatest marvels of the age is the immense 

 interest attaching to this series of apparatus. In a 

 sense, the excitement consequent on the demonstration of 

 the practicability of electric lighting is less, ina.smuch as for 

 several decades past that subject htis been periodically 

 revived in the minds of scientific men. Notwithstanding 

 the fact, however, that secondary batteries are now In^fore 

 the general public for the first time, it must not by any 

 m<aiis be supposMl that they arc novelties to the Ijcttcr- 

 informed physicists. 



It is not necessarj', nor would it l>e advisable, for us to 

 go back eighty or more years to lay W-fore our readers the 

 history of the secondary battery and the principles that 

 govern it We will pass over the preliminary but im- 



portant work of Calvani, Volta, Hitter, and a number of 

 otlier devotees, pausing to say a word or two about tho 

 celebrated gas battery of Sir William tirovo, which may bo 

 said to embrace the fundamental principles of secondary 

 batteries. 



"In this battery each cell consists of a vessel containing, 

 acidulated water, in which the lower portions of two 

 platinum plates are immersed, their upper portions being, 

 surrounded, one by oxygen and the otlier by liydrogen,. 

 enclosed in inverted tubes. Each tube has a platinum 

 wire passing through its upper end and connected with the. 

 enclosed plate. These wires are tho terminals of tho. 

 separate cells, and in combining a number of cells into a 

 battery, the oxygen tube of one cell must be connected 

 with the hydrogen tube of the next When the circuit is 

 completed a current circulates, opposite to that whick 

 would have evolved the gases from the acidulated water,, 

 and the quantity of gas in the tubes diminishes. Chemical 

 combination, in fact, goes on betweeii the two gases of any 

 one cell through the intervention of the acidulated water. 

 The plates employed in this battery are usually coverect 

 with a deposit of finely-divided platinum, which increases, 

 the rapidity of the action."* This late feature is some- 

 what important With a gas battery of fifty pairs, Grove 

 produced electric lights, eti'ected various chemical decom- 

 positions, itc. 



To M. Gaston Plante, however, more than to any 

 other man, justly belongs tlie first place of honour in this 

 branch of scientific labour. It is a most remarkable fact 

 that the very thing which the general body of practical 

 workers regard as an obstacle other men take up, and by 

 its means confer an immeasurable boon on humanity. It 

 was so in the case of M. Plante. Electricians had strivea 

 very hard to rid themselves of the troubles arising from 

 what is called tho " polarisation of the battery." For this 

 purpose the Daniell cell was invented, which to this day 

 stands forward as pre-eminently the best for the ordinary 

 requirements of telegraphy. Polarisation results in the 

 deposition of one or more of the constituents of th(! 

 liquid in the cell on one of the plates. In the simple 

 cell, with zinc and copper immersed in acidulated 

 water, the zinc is oxidised, and converted into zincic 

 sulphate, while hydrogen gas is deposited on tho copper 

 plate. Inashoit time this hydrogen becomes a powerful 

 source of an opposing current, the cell being then useless. 

 Substituting a simple metallic salt for the acid, the metal 

 is, generally speaking, deposited on the copper, or whatever 

 sul)stance may constitute the negative plate ; the acid 

 portion of tho salt comliining with the zinc, or positive 

 l>late. But the same thing which takes place in the battery- 

 cell may be made to occur in any part of a battery circuit. 

 Here, then, lies a part at least of the action of Grove's Gas. 

 J'attery. A current, in passing through the water, de- 

 composed it, the two constituent gases — oxygen and hydro- 

 gen — accumulating, the former at the positive electrode, or 

 point of entry of the current, and the latter at the negative- 

 electrode, or point of exit 



This principle may be seen elsewhere, for wherever we. 

 pa.ss electricity through a compound liquid, a change in the. 

 chemical relationship may be found, and this change will 

 always be such as will tend to generat<; an electric forcft 

 opposite in direction tf) that which brought about its exis- 

 tence. Such, then, is "polarisation." liriedy defined, we. 

 may say that " polarisation is the electric re-action at 

 the poles or electrodes of a cell, and is of the nature 

 of a countf;r-electromotive force." How M. Plante made, 

 use of this polarisation, we will say in our next 



I 



DoBchanel's " Xatural Philosophy." 



