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SCIENTIFIC SIDE-LIGHTS 



264 



the equivalent of 822,600 foot-pounds; that 

 is, a power which would raise nearly four 

 tons to the height of one hundred feet. 

 COOKE New Chemistry, lect. 1, p. 25. (A., 

 1899.) 



1286. FORCE, FIELD OF, ABOUT A 



MAGNET Iron-Mings Supposed Raving to 

 Escape. Even more remarkable than this 

 is his [Lucretius's] statement that iron- 

 filings " will rave within brass basins " when 

 the stone is placed beneath. This was the 

 first perception of the field of force about 

 a magnet, by noting not merely the effect 

 of its attraction or repulsion exerted upon 

 the pole of another magnet brought into 

 it, but upon loose iron-filings free to dis- 

 pose themselves therein along the lines of 

 force. Then, under the astonished gaze of 

 the poet, the particles of metal arranged 

 themselves in the curious curves of the mag- 

 netic spectrum, and rose like bristles in 

 front of the poles. And as he moved the 

 stone beneath the brass basin which held 

 them, he saw them fly from one side of it 

 to the other, sometimes grouping themselves 

 for an instant in dense bunches, then leap- 

 ing apart and scattering all so incoherently 

 and so wildly that it is small wonder that 

 he regarded them as raving in their fran- 

 tic desire to break away from the myste- 

 rious force. PARK BENJAMIN Intellectual 

 Rise in Electricity, ch. 2, p. 50. (J. W., 

 1898.) 



1287. FORCE, LIVING, OF MOVING 

 BODIES Vis Viva Increase as Square of 

 Velocity. In mechanics, the product of the 

 mass of a moving body into the square of 

 its velocity expresses what is called the 

 vis viva, or living force. It is also some- 

 times called the " mechanical effect." If, 

 for example, a cannon pointed to the zenith 

 urge a ball upwards with twice the velocity 

 imparted to a second ball, the former will 

 rise to four times the height attained by 

 the latter. If directed against a target, it 

 will also do four times the execution. Hence 

 the importance of imparting a high velocity 

 to projectiles in war. TYNDALL Fragments 

 of Science, vol. i, ch. 1, p. 15. (A., 1897.) 



1288. FORCE, MAGNETIC, LINES OF 



Iron-filings Grouped around Poles of Mag- 

 ne t. Placing a sheet of paper or glass over 

 a bar magnet and showering iron-filings upon 

 the paper, I notice a tendency of the filings 

 to arrange themselves in determinate lines. 

 They cannot freely follow this tendency, for 

 they are hampered by the friction against 

 the paper. They are helped by tapping the pa- 

 per ; each tap releasing them for a moment, 

 and enabling them to follow their tendencies. 

 . . . The aspect of these curves so fas- 

 cinated Faraday that the greater portion 

 of his intellectual life was devoted to pon- 

 dering over them. He invested the space 

 through which they run with a kind of 

 materiality; and the probability is that the 

 progress of science, by connecting the phe- 

 nomena of magnetism with the luminiferous 



ether, will prove these " lines of force," as 

 Faraday loved to call them, to represent a 

 condition of this mysterious substratum of 

 all radiant action. TYNDALL Lectures on 

 Light, lect. 3, p. 98. (A., 1898.) 



1289. FORCE, MAN UTILIZES, BUT 

 DOES NOT CREATE Property in Forces- 

 Wind and Stream. We cannot create me- 

 chanical force, but we may help ourselves 

 from the great storehouse of Nature. The 

 brook and the wind which drive our mills, 

 the forest and the coal-bed which supply 

 our steam-engines and warm our rooms, are 

 to us the bearers of a small proportion of 

 the great natural supply which we draw 

 upon for our purposes, and the action of 

 which we can apply as we see fit. The 

 possessor of a mill claims the gravity of 

 the descending rivulet or the living force 

 of a moving wind as his possession. These 

 portions of the store of Nature are what 

 give his property its chief value. HELM- 

 HOLTZ Interaction of Natural Forces, p. 

 227. (Translated for Scientific Side-Lights.) 



1290. FORCE MISAPPLIED Lubrica- 

 tion Converges Power on Work. So also 

 with regard to the greasing of a saw by a 

 carpenter. He applies his force with the 

 express object of cutting through the wood. 

 He wishes to overcome mechanical cohesion 

 by the teeth of his saw, and, when it moves 

 stiffly, the same amount of effort may pro- 

 duce a much smaller effect than when the 

 implement moves without friction. But in 

 what sense smaller? Not absolutely so, but 

 smaller as regards the act of sawing. The 

 force not expended in sawing is misapplied, 

 not lost; it is converted into heat. Here 

 again, if we could collect the heat engen- 

 dered by the friction, and apply it to the 

 urging of the saw, we should make good the 

 precise amount of work which the carpen- 

 ter, by neglecting the lubrication of his im- 

 plement, had simply converted into another 

 form of power. TYNDALL Heat a Mode of 

 Motion, lect. 1, p. 9. (A., 1900.) 



1291. FORCE OF CRYSTALLIZATION 



Wonderful Property of Lifeless Matter. 

 Gravitation . . . consists of an attrac- 

 tion of every particle of matter for every 

 other particle. You know that planets and 

 moons are held in their orbits by this at- 

 traction. But gravitation is a very simple 

 affair compared to the force, or rather 

 forces, of crystallization. For here the ulti- 

 mate particles of matter, inconceivably 

 small as they are, show themselves possessed 

 of attractive and repellent poles, by the mu- 

 tual action of which the shape and structure 

 of the crystal are determined. In the solid 

 condition the attracting poles are rigidly 

 locked together ; but if sufficient heat be ap- 

 plied the bond of union is dissolved, and in 

 the state of fusion the poles are pushed so 

 far asunder as to be practically out of each 

 other's range. The natural tendency of the 

 molecules to build themselves together is 

 thus neutralized. This is the case with 



