461 



SCIENTIFIC SIDE-LIGHTS 



Motion 



ments he uses the following remarkable 

 language : " It will be convenient to begin 

 with an instance or two of the production 

 of heat, wherein there appears not to inter- 

 vene anything on the part of the agent or 

 patient but local motion and the natural 

 effects of it. When, for example, a smith 

 does hastily hammer a nail or such like 

 piece of iron the hammered metal will grow 

 exceedingly hot; and yet there appears not 

 anything to make it so, save the forcible 

 motion of the hammer, which impresses a 

 vehement and variously determined agita- 

 tion of the small parts of the iron, which, 

 being a cold body before, by that superin- 

 duced commotion of its small parts, be- 

 comes in divers senses hot; first, in a more 

 lax acceptation of the word in reference to 

 some other bodies, in respect of whom it 

 was cold before, and then sensibly hot; 

 because this newly gained agitation sur- 

 passes that of the parts of our fingers. 

 TYNDALL Heat a Mode of Motion, lect. 1, p. 

 34. (A., 1900.) 



2259. MOTION CREATING HEAT 



Fire Kindled by Friction. Taking an elastic 

 stick about eighteen inches long, he [the 

 Guacho on the pampas] presses one end on 

 his breast and the other (pointed) end into 

 a hole in a piece of wood, and then rapidly 

 turns the curved part, like a carpenter's 

 center-bit. DARWIN Naturalist's Voyage 

 around the World, ch. 18, p. 409. (A., 

 1898.) 



2260. MOTION ESSENTIAL TO LIFE 



Air and Water Made Habitable by Move- 

 ment. It is not enough that we have the 

 air in which we live and move, with all 

 of its properties, as we have described: 

 something more is needed which is abso- 

 lutely essential both to animal and vege- 

 table life, and this essential is motion. If 

 the air remained perfectly still, with no 

 lateral movement or upward and downward 

 currents of any kind, we should have a per- 

 fectly constant condition of things, subjected 

 only to such gradual changes as the ad- 

 vancing and receding seasons would produce 

 owing to the change in the angle of the sun's 

 rays. No cloud would ever form, no rain 

 would ever fall, and no wind would ever 

 blow. It is of the highest importance not 

 only that the wind shall blow, but that com- 

 paratively sudden changes of temperature 

 take place in the atmosphere, in order that 

 vegetation as well as animal life may exist 

 upon the surface of the globe. The only 

 place where animal life could exist would 

 be in the great bodies of water, and it is 

 even doubtful if water could remain habit- 

 able unless there were means provided 

 for constant circulation motion. ELISHA 

 GRAY Nature's Miracles, vol. i, ch. 6, p. 45. 

 (F. H. & H., 1900.) 



2261. MOTION, HEAT LONG KNOWN 

 AS Locke Foreshadows Molecular Theory. 

 In his " Essay on the Human Understand- 

 ing " Locke frequently refers to heat as 



being a kind of motion. But the very re- 

 markable utterance which of late years has 

 been most widely circulated is the follow- 

 ing: "Heat," says Locke, "is a very brisk 

 agitation of the insensible parts of the ob- 

 ject, which produces in us that sensation 

 from whence we denominate the object hot; 

 so what in our sensation is heat, in the 

 object is nothing but motion. This appears 

 by the way heat is produced; for we see 

 that the rubbing of a brass nail upon a 

 board will make it very hot, and the axle- 

 trees of carts and coaches are often hot, 

 and sometimes to a degree that it sets them 

 on fire, by the rubbing of the naves of the 

 wheels upon them. On the other side, the 

 utmost degree of cold is the cessation of that 

 motion of the insensible particles, which 

 to our touch is heat." LOCKE Works, vol. 

 iv, p. 597, ed. of 1768, quoted by TYNDALL 

 in Heat a Mode of Motion, lect. 2, p. 37. 

 (A., 1900.) 



2262. MOTION MAGNIFIED EQUALS 

 TIME EXTENDED The Telescope Gives the 

 Astronomer a Record of Ten Thousand 

 Tears. The magnifying power of the tele- 

 scope in reality acts to magnify any effects 

 of star motion. So that if a magnifying 

 power of 100 is used, the astronomer could 

 detect in one year any motion which, to the 

 naked eye, would only be discernible in one 

 hundred years. 



Very few motions are discernible to ordi- 

 nary vision (aided, of course, by an instru- 

 mental index devised to determine a star's 

 place) in so short a time as one hundred 

 years. But notice that in twenty or thirty 

 years a telescopist, using the very moderate 

 power named, would be able to detect a mo- 

 tion which ordinary vision would be able to 

 recognize [only] after the lapse of two thou- 

 sand or three thousand years. And our as- 

 tronomers are not limited to twenty or thirty 

 years. They can compare their observations 

 with those made by such observers as Brad- 

 ley and his contemporaries nearly a century 

 and a half ago. This amounts, with moder* 

 ate telescopic power, to the observation of 

 effects equivalent to those which would be 

 presented to the naked eye in the course of 

 more than ten thousand years. PROCTOR 

 Expanse of Heaven, p. 281. (L. G. & Co., 

 1897.) 



2263. MOTION NOT TO BE TRANS- 

 MUTED INTO SENSATION Thought Can- 

 not Be Expressed in Terms of Chemistry. 

 We can prove that bile arises in the liver by 

 chemical processes which we are able, in 

 part at least, to follow out in detail. We 

 can show, too, that movement is produced in 

 muscles by definite processes, which are 

 again the immediate result of chemical 

 transformation. But cerebral processes 

 give us no shadow of indication as to how 

 our mental life comes into being. For the 

 two series of phenomena are not comparable. 

 We can conceive how one motion may be 

 transformed into another, perhaps also how 



