567 



SCIENTIFIC SIDE-LIGHTS 



Purity 

 Purpose 



of dust. But, what is far more important 

 than the color of sky and beauty of sunset, 

 dust gives us also diffused daylight, or sky- 

 light, that most equable and soothing and 

 useful of all illuminating agencies. With- 

 out dust the sky would appear absolutely 

 black, and the stars would be visible even 

 at noonday. The sky itself would, therefore, 

 give us no light. We should have bright, 

 glaring sunlight or intensely dark shadows, 

 with hardly any half-tones. From this cause 

 alone the world would be so totally differ- 

 ent from what it is that all vegetable and 

 animal life would probably have developed 

 into very different forms, and even our own 

 organization would have been modified in 

 order that we might enjoy life in a world 

 of such harsh and violent contrasts. WAL- 

 LACE The Wonderful Century, ch. 9, p. 82. 

 (D. M. & Co., 1899.) 



2797. 



Law of Structure 



Subordinate to Law of Purpose Man and 

 Gorilla. Professor Huxley, in his work on 

 " Man's Place in Nature," has endeavored 

 to prove that, so far as mere physical struc- 

 ture is concerned, " the differences w T hich 

 separate him from the gorilla and the chim- 

 panzee are not so great as those which 

 separate the gorilla from the lower apes. ! ' 

 On the frontispiece of this work he exhibits 

 in series the skeletons of the anthropoid 

 apes and of man. It is a grim and grotesque 

 procession. The form which leads it, how- 

 ever like the others in general structural 

 plan, is wonderfully different in those lines 

 and shapes of matter which have such mys- 

 terious power of expressing the characters 

 of mind. And significant as those differ- 

 ences are in the skeleton, they are as noth- 

 ing to the differences which emerge in the 

 living creatures. Huxley himself admits 

 that these differences amount to " an enor- 

 mous gulf," to a " divergence immeasurable 

 practically infinite." What more striking 

 proof could we have than this, that organic 

 forms are but as clay in the hands of the 

 potter, and that the " law of structure " is 

 entirely subordinate to the " law " of pur- 

 pose and intention under which the various 

 parts of that structure are combined for 

 use? ARGYLL Reign of Law, ch. 5, p. 157. 

 (Burt.) 



2798. Manifold Adapta- 

 tions One Design No Disproof of Another 

 Adaptation of Grain both to Reproduction 

 and to Food. To perceive intention is a 

 very different thing from perceiving all that 

 is intended. Our own human experience 

 should make this distinction familiar to us. 

 Many things we do and many things we con- 

 trive are done and contrived with more than 

 one intention. In the light of this experi- 

 ence it is altogether irrational to regard 

 as an exception to the attainment of pur- 

 pose in Nature the fact, for example, " that 

 of fifty seeds she often brings but one to 

 bear." It throws no doubt or difficulty in 

 the way of our conviction, for example, that 



one purpose of seed-bearing in plants is the 

 reproduction of their kind, because it ap- 

 pears that another purpose to which that 

 seed-bearing is applied is the support of 

 animal life. The intention with which a 

 grain of wheat is so constituted as to be 

 capable of producing another wheat plant 

 is not the less in the nature of purpose be- 

 cause it coexists with another intention, 

 that the same grain should be capable of 

 sustaining the powers and the enjoyments 

 of life in the body and in the mind of man. 

 On the contrary, the power possessed by 

 most plants, and by this plant especially, 

 of producing seed in a ratio far beyond that 

 which would be required for one purpose, 

 is the sure indication and the proof that 

 another purpose larger and wider was in 

 view. ARGYLL Reign of Law, ch. 4, p. 104. 

 ( Burt. ) 



2799. Movement of Leaves 



of Plants. As the upward movements of 

 the leaflets of Robinia, and the downward 

 movements of those of Oxalis, have been 

 proved to be highly beneficial to these plants 

 when subjected to bright sunshine, it seems 

 probable that they have been acquired for 

 the special purpose of avoiding too intense 

 an illumination. DARWIN Power of Move- 

 ment in Plants, ch. 8, p. 453. (A., 1900.) 



28OO. Plain Coloring of 



Female Birds Final Not Identical icith 

 Physical Cause. Utility, indeed, in a dif- 

 ferent sense, can be quoted with proba- 

 bility, as accounting for the comparative 

 plain coloring of females in this and in 

 almost all other genera of birds. But then 

 it is utility conceived as operating by way 

 of motive in a creative mind, and not oper- 

 ating as a physical cause in the production 

 of a mechanical result. And here we find 

 Mr. Wallace instinctively testifying to this 

 great distinction, and employing language 

 which indicates the passage from one order 

 of ideas to another. He says, " The reason 

 why female birds are not adorned with equal- 

 ly brilliant plumes is sufficiently clear; they 

 would be injurious by rendering : their pos- 

 sessors too conspicuous during incubation." 

 [Quarterly Journal of Science, October, 1867, 

 p. 481.] This is, no doubt, the true ex- 

 planation of the purpose which the plain 

 coloring of female birds is intended to 

 serve; but it is no explanation at all of 

 the physical causes by which this special 

 protection is secured. ARGYLL Reign of 

 Law, ch. 5, p. 137. (Burt.) 



28O1. 



The Extermination 



of Useless Organisms. Nature is purpose- 

 ful, not only in adapting recently developed 

 structures to her uses i. e., in fitting them 

 to perform properly the functions allotted to 

 them but conversely, in removing every- 

 thing superfluous, so that as soon as a 

 structure is no longer required it is elimi- 

 nated. Of course, this elimination is neither 

 sudden nor voluntary, but comes to pass 



