348 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



its only basis, requires not merely that we should 

 never disguise a difficulty, but, on the contrary, 

 that we should call special attention to it, as a 

 probable source of valuable information. If you 

 meet with an author who, like the cuttle-fish, en- 

 deavors to escape from a difficult position by 

 darkening all around him with an inky cloud of 

 verbiage, close the book at once and seek infor- 

 mation elsewhere." 



But I must come back to the really important 

 point, which is this : 



True science is in itself simple, and should be 

 explained in as simple and definite language as 

 possible. 



Word-painting finds some of its most ap- 

 propriate subjects when employed to deal with 

 human snobbery or human advice — where the 

 depraved tastes and wills of mortals are con- 

 cerned — not the simple and immutable truths 

 of science. Battles, murders, executions ; po- 

 litical, legal, and sectarian squabbles ; gossip, 

 ostentation, toadyism, and such like, are of its 

 proper subjects. Not that the word-painter need 

 be himself necessarily snobbish or vicious — far 

 from it. But it is here, as our best poets and 

 satirists have shown, that his truest field is to be 

 found. Science sits enthroned, like the gods of 

 Epicurus, far above the influence of mere human 

 passions, be they virtuous or evil, and must be 

 treated by an entirely different code of rules. 

 And a great deal of the very shallowest of the 

 pseudo-science of the present day probably owes 

 its origin to the habitual use, with reference to 

 physical phenomena, of terms or synonyms whose 

 derivation shows them to have reasonable appli- 

 cation to human beings and their actions alone — 

 cot at all to matter and energy. In dealing with 

 such pseudo-science it is, of course, permissible 

 to me, even after what I have said, to use word- 

 painting as far as may be thought necessary. 



The Pygmalions of modern days do not re- 

 quire to beseech Aphrodite to animate the ivory 

 for them. Like the savage with his totern, they 

 have themselves already attributed life to it. " It 

 comes," as Helmholtz says, " to the same thing as 

 Schopenhauer's metaphysics. The stars are to 

 love and hate one another, feel pleasure and dis- 

 pleasure, and to try to move in a way correspond- 

 ing to these feelings." The latest phase of this 

 peculiar non-science tells us that all matter is 

 alive ; or, at least, that it contains the " promise 

 and potency " (whatever these may be) " of all 

 terrestrial life." All this probably originated in 

 the very simple manner already hinted at ; viz., 



in the confusion of terms constructed for applica- 

 tion to thinking beings only, with others appli- 

 cable only to brute matter, and a blind following 

 of this confusion to its necessarily preposterous 

 consequences. So much for the attempts to in- 

 troduce into science an element altogether incom- 

 patible with the fundamental conditions of its ex- 

 istence. 



When simple and definite language cannot be 

 employed, it is solely on account of our ignorance. 

 Ignorance may, of course, be either unavoidable 

 or inexcusable. 



It is unavoidable only when knowledge is not 

 to be had. But that of which there is no knowl- 

 edge is not yet part of science. All we can do 

 with it is simply to confess our ignorance and 

 seek for information. 



As an excellent illustration of this we may 

 take two very common phenomena — a rainbow 

 and an aurora — the one, to a certain extent at 

 least, thoroughly understood ; the other scarcely 

 understood in almost any particular. Yet it is 

 possible that, in our latitudes at least, we see the 

 one nearly as often as the other. For, though 

 there are probably fewer auroras to be seen than 

 rainbows, the one phenomenon is in general much 

 more widely seen than the other. A rainbow is 

 usually a mere local phenomenon, depending on 

 a rain-cloud of moderate extent; while an aurora, 

 w,hen it occurs, may extend over a whole terres- 

 trial hemisphere. Just like total eclipses, lunar 

 and solar. Wherever the moon can be seen, the 

 lunar eclipse is visible, and to all alike. But a 

 total solar eclipse is usually visible from a mere 

 strip of the earth — some 50 miles or so in breadth. 



The branch of natural philosophy which is 

 called Geometrical Optics is based upon three ex- 

 perimental facts or laws, which are assumed as 

 exactly true, and as representing the whole truth 

 — the rectilinear propagation of light in any one 

 uniform medium, and the laws of its reflection and 

 refraction at the common surface of two such 

 media — and as a science it is nothing more than 

 the developed mathematical consequences of these 

 three postulates. 



Hence, if these laws were rigorously true, and 

 represented all the truth, nothing but mathemat- 

 ical investigation based on them would be re- 

 quired for the complete development of the phe- 

 nomena of the rainbow — except the additional 

 postulate, also derived from experiment, that fall- 

 ing drops of water assume an exact spherical form 

 — and, as data for numerical calculation, the ex- 

 perimentally-determined refractive index for each 

 ray of light at the common surface of air and water. 



