263 



SCIENTIFIC SIDE-LIGHTS 



Food 

 Force 



quantity of carbon it contains, stands near- 

 est to coal. We heat our bodies precisely 

 as we heat a stove, with fuel that contains 

 the same elements as wood and coal, but 

 differs essentially from the latter substances 

 in being soluble in the juices of the body. 

 LIEBIG Ucber die Verwandlung der Krdfte 

 (Sammlung wissenschaftlicher Vortrdge, ge- 

 halten zu Miinchen, 1858, p. 594). (Trans- 

 lated for Scientific Side-Lights.) 



1280. FORCE A REFLECTION OF 

 MAN'S CONSCIOUS EFFORT If we trace 

 all our conceptions on the nature of force 

 to their fountain-head, we shall find that 

 they are formed on our own consciousness 

 of living effort of that force which has its 

 seat in our own vitality, and especially on 

 that kind of it which can be called forth at 

 the bidding of the will. ARGYLL Reign of 

 Law, ch. 2, p. 72. (Burt.) 



1281. FORCE, ATOMIC, EXCEEDS 

 GRAVITATION Energy Required to Heat a 

 Pound Would Lift Tons. As measured by 

 any ordinary mechanical standard, the mag- 

 nitude of the forces engaged in this atomic 

 motion and interior work is enormous. A 

 pound of iron, on being heated from C. 

 to 100 C., expands by about ^th of the 

 volume which it possesses at 6. Its aug- 

 mentation would certainly escape the most 

 acute eye; still, to give its atoms the mo- 

 tions corresponding to this increase of tem- 

 perature, and to shift them through the 

 small space indicated, an amount of heat is 

 requisite which would raise a weight of 

 about eight tons one foot high. The force 

 of gravity almost vanishes in comparison 

 with these molecular forces; the pull of the 

 earth upon our pound weight, as a mass, is 

 as nothing compared with the mutual pull 

 of its own atoms. TYNDALL Heat a Mode 

 of Motion, lect. 7, p. 185. (A., 1900.) 



1282. FORCE, BRUTE, AT HIGHEST 

 POINT ERE MAN APPEARS Human In- 

 telligence Conquers Giant Mammals Be- 

 come Extinct. The earlier mammalia were 

 giants in comparison with those now living. 

 The mastodon and mammoth as compared 

 with the modern elephant, the megatherium 

 as compared with the sloth or ant-eaters 

 of present times, the hyenas and bears of 

 the European caverns, and the fossil elk 

 of Ireland, by the side of which even the 

 moose of our Northern woods is belittled, 

 are remarkable instances in proof of this. 

 One cannot but be struck with the fact 

 that this first representation of mammalia, 

 the very impersonation of brute force in 

 power, size, and ferocity, immediately pre- 

 ceded the introduction of man, with whose 

 creation intelligence and moral strength be- 

 came the dominant influences on earth. 

 AGASSIZ Geological Sketches, ser. i, ch. 

 7, p. 195. (H. M. & Co., 1896.) 



1283. FORCE, ELECTRICAL Fara- 

 day's Discovery Marvelous Applications 

 within Fifty Years. It is only a little over 



half a century since Faraday made his 

 disco very [of the production of an electrical 

 current by the movement of a conducting 

 body in a magnetic field]. As a result of 

 this observation, so apparently unimpor- 

 tant, we see to-day an entirely new curric- 

 ulum of study in all of our great schools. 

 The science of electrical engineering is a 

 direct outgrowth of Faraday's observation. 

 We have seen already a complete revolution 

 in the methods of transporting passengers 

 in cities, growing out of this discovery. Rap- 

 idly are coming changes in the transmis- 

 sion of energy and in the utilization of the 

 waste forces of Nature. Torrents and cata- 

 racts are made to do valuable work for hu- 

 manity hundreds of miles from their locali- 

 ties. A new system of illumination has 

 sprung up over the whole civilized world, 

 displacing oil and gas. It requires no proph- 

 et to foresee the day when the development 

 of electrical energy made possible by Fara- 

 day's discovery will be accomplished far 

 more economically than at the present, 

 perhaps even permitting the direct conver- 

 sion of burning fuel into electrical force. 

 . . Could there be a more striking il- 

 lustration of what a discovery in pure sci- 

 ence, developed by skilful technologists, can 

 do in the promotion of human industry? 

 WILEY Relations of Chemistry to Indus- 

 trial Progress (Address at Purdue Univer- 

 sity, Lafayette, Ind., 1896, p. 21). 



1 284. FORCE, ENORMOUS, OF CHEM- 

 ICAL COMBINATION Measured in Terms of 

 Falling Body. It has been stated that when 

 a body falls to the earth it is warmed by 

 the shock. Here, to use the terminology 

 of Mayer, we have a mechanical combina- 

 tion of the earth and the body. Let us suf- 

 fer the falling body and the earth to dwin- 

 dle in imagination to the size of atoms, 

 and for the attraction of gravity let us sub- 

 stitute that of chemical affinity; we have 

 then what is called a chemical combination. 

 The effect of the union in this case also is the 

 development of heat, and from the amount 

 of heat generated we can infer the inten- 

 sity of the atomic pull. Measured by or- 

 dinary mechanical standards, this is enor- 

 mous. Mix eight pounds of oxygen with 

 one of hydrogen, and pass a spark through 

 the mixture; the gases instantly combine, 

 their atoms rushing over the little distances 

 which separate them. Take a weight of 

 47,000 pounds to an elevation of 1,000 feet 

 above the earth's surface, and let it fall; 

 the energy with which it will strike the 

 earth will not exceed that of the eight 

 pounds of oxygen atoms as they dash 

 against one pound of hydrogen atoms to 

 form water. TYNDALL Fragments of Sci- 

 ence, vol. i, ch. 1, p. 10. (A., 1897.) 



1285. FORCE EXPENDED TO CON- 

 VERT WATER INTO STEAM In order to 

 pull apart the molecules of a pound of 

 water, that is, convert it into steam, we 

 must exert a mechanical power which is 



