192 



♦ KNOWLEDGE o 



[March 30, 1883. 



another way — as by roasting, A-c. 7. That jellies ought 

 always to >>e associated with some other principles to 

 render them both nutritive and digestible.* 



The reader may make a very simple experiment on 

 himself by preparing first a pure gelatine soup from 

 isinglass, or the prepared gelatine commonly sold, and 

 trj'ing to make a meal of this with bread alone. Its 

 insipidity will be evident with the first spoonfull. If he 

 perseveres, it will become not merely insipid, but positively 

 repulsive ; and should he struggle through one meal and 

 tlien another, without any other food between, he will find 

 it, in the course of time (^•aryiIlg with constitution and 

 previous alimentation), positively nauseous. 



Let him now add to it some of Liebig's Extract of Meat, 

 and he will at once perceive the difference. Here the 

 natural appetite foreshadows the result of continuing the 

 experiment, and points the way to correcting the errors of 

 the Academicians and Baron Liebig. The jellies that we 

 take at evening parties, or the jujubes used as sweetmeats, 

 are flavoured with something positive. I have tasted " Blue- 

 Ribbon " jellies that were wretchedly insipid. This was 

 not merely owing to the absence of alcohol, of which 

 very little can remain in such preparations, but rather 

 to the absence of the flavouring ingredients of the 

 sherry. The Rahat Lako^on, or " lumps of delight," 

 sold in the streets of Constantinople, is gelatine flavoured 

 with the unfermented juices of fruit. A privileged 

 visit which I once made to the monster kitchen of the Old 

 Seraglio of his Majesty the Sultan (at Stamboul), lives 

 perpetually in my memory, so sweetly, so vividlj', and so 

 gratefully, that when I find myself defending the Turk 

 against the Russian and all his other enemies, my con- 

 science sometimes inquires whether those lumps of delight 

 prepared for the Sultana by his Highness the Grand Con- 

 fectioner, and presented to me by him as a sample of his 

 masterpiece, may, or may not, have ever after influenced 

 my politics. It was gelatine glorified, once tasted never to 

 be forgotten. 



It would seem that gelatine alone, although containing 

 the elements required for nutrition, requires something 

 more to render it digestible. We shall probably be not 

 far from the truth if we picture it to the mind as some- 

 thing too smooth, too neutral, too inert, to set the digestive 

 organs at work, and that it therefore requires the addition 

 of a decidedly sapid something that shall make these 

 organs act. 1 believe that the proper function of the palate 

 is to determine our selection of such materials ; that its 

 activity is in direct sympathy with that of all the digestive 

 organs ; and that if we carefully avoid the vitiation of 

 our natural appetites, we have in our mouths, and the 

 nervous apparatus connected therewith, a laboratory that 

 is capable of supplying us with information concerning 

 some of the chemical relations of food which is beyond 

 the grasp of the analytical machinery of the ablest of our 

 scientiKc chemists. 



There is another element of flesh so intimately connected 

 with gelatine and so much like it, that T must describe its 

 properties before going further into the subject of practical 

 cookery of animal food. I refer to fbrin, "which will form 

 the subject of my next paper. 



It is bolieved that the Edison Company have entered 

 into an agr,>ement to light the Cieneral Po.st Office by 

 means of 1,500 Edison lamps, the current being supplied 

 from tho station on the Holbom Viaduct 



• Londe, " Nouveaux fiU-mens d'Hygiftne," Second Edition, 

 Tol. ii., ]>. 73. 



" ENERGY." 



By E. C. Ri.mixgtos, 



Srhool nf Electrical Kn'jinceriii'j, Priiices-Klrect, Ifdiiocer-Hquare. 



IN looking over some back numbers of a leading electrical 

 journal, I came across the following advertisement : — 



A Hint from Poor Man to Elect rici.ans and Ottiers. — A properly- 

 constructed ptrmanent ma^eto-dynaino shoald oSfer no resistance 

 to tbe driving power, except simple friction of bearings. This 

 can be acconiplislied. 



Tlie mere fact of such an advertisement being written 

 must show that there are numbers of persons who do not 

 understand the simplest facts concerning the conservation 

 of energy. I propose in this article, therefore, to set for- 

 ward, in as simple and untechnical language as possible, a 

 few of the most elementary of these facts. 



Perhaps the best definition of energy is " that which is 

 absorbed or transformed when work is done." 



Work, consequently, is a transformation of energy. The 

 word work is here used in a sense having a far wider signi- 

 fication than what is popularly understood by the term. 

 If we bum a pound of coal, we absorb or transform the 

 energy contained in that coal (energy stored up in the 

 coal in bygone years, when the light of the sun split up 

 the carbonic acid gas in the air, liberating the oxygen, and 

 depositing the carbon to form wood, which in the course of 

 ages became transformed into coal), we do not destroy it ; 

 energy cannot be destroyed, neither can it be created. The 

 energy absorlied in burning the pound of coal is converted 

 into the heat produced ; it may be lost for all practical 

 purposes, or it may be employed to perform useful work, 

 as, for instance, to drive an engine. If we wind up the 

 spring of a clock, we store up energy in the spring : when we 

 start the clock and allow the spring to uncoil itself, the energy 

 stored up in the spring is absorbed in doing the work of 

 driving the clock. Again, suppose we put a charge of 

 powder and a bullet into a rifle, then explode the powder ; 

 the bullet is propelled out of the rifle by part of the energy 

 stored up in the powder. This may be regarded as the 

 practically useful work done ; the other part of the energy 

 stored up in the powder is absorbed in the work performed 

 in heating the rifle, and may be regarded as the practically 

 useless work produced by the absorption of energy. Xow, 

 let us suppose that the bullet, upon which work was done, 

 comes in contact with an immovable iron target, the energy 

 stored up in the bullet, by reason of the work done upon it, 

 becomes converted into heat. 



If we raise a weight from tbe ground, thus performing 

 work on it, we store up energy in it, which is greater the 

 higher we raise it, and the larger the weight. On allowing 

 it to fall to the ground, the weight does as much work as 

 w-as done on it in raising it. The energy stored up in the 

 weight after it has been raised is termed potential energy, 

 and is similar to that which was stored in the wound-up 

 clock-spring. Potential energy is stored up when work is 

 done against forces, which, like gravity, are independent of 

 the motion of the moving body. If, now, we place our 

 weight on a horizontal plane, and move it from one place 

 on this plane to another, we likewise perform work on it. 

 But there is no energy now stored up in it which will 

 enable it to do work in return for the work done upon it. 

 In this case we do work against friction, a force which is 

 reversed as soon as the direction of motion is reversed, and 

 which, consequently, opposes this motion ; in overcoming 

 this friction an amount of heat is produced which is 

 equivalent to the work so done. In the heat produced is 

 stored up the energy produced by the work done in mo\-ing 

 the weight against the opposing force of friction. 



