112 KANSAS Academy of science. 



of these two ideas led to the distinction between the heavens outside of and the sky 

 lying within our atmosphere. The rise of the distinction manifests itself on the one 

 hand in painting; for whereas the early painters portrayed the sky as the ancients 

 saw it, a vaulted dome of blue, hard and without depth, the growth of the art has 

 been marked throughout by more and more successful attempts at atmospheric 

 effect, at intangibility and depth. Where the earlier artists saw and painted only a 

 blue surface, members of later schools — the landscape painters above all — began 

 to indicate the truths of aerial perspective which had already forced themselves upon 

 the attention of observing men, while it remained for a Turner and a Ruskin to give, 

 with brush and pen, that fuller expression of the subtler beauties of the sky which 

 increasing knowledge and the assthetic training of generations have made possible 

 to art. 



In this, as in other ways, the development of science and of art have gone hand 

 in hand, and it would be easy to trace the influence of Tycho Brahe and Galileo, of 

 Otto von Guericke and Newton, upon the growth of a?sthetica. 



Of theories of the cause of the most obvious characteristic of the sky — its blue- 

 ness — there have been no lack since men began to speculate. There was, however, 

 no basis for intelligent theorizing until the experiments of Torricelii and von Guericke 

 had shown the existence of an atmosphere, and the great chain of truths made clear 

 by their investigations had had time to become familiar to the common mind. 

 Even then there was no intelligible theory of colors, and the world must needs wait 

 for Newton's prism before it could deal successfully with the problem of the color of 

 the sky. The host of hypotheses which had been formed during the Middle Ages, 

 were based upon so crude a conception of the nature of color that they melted in- 

 stantly before the flood of light which was jioured into the world of optics by 

 Newton's analysis of the sunbeam. In the words inscribed upon a tablet at his 



birthplace — 



" Nature and Nature's laws lay hid in night; 

 God said 'Let Newton be,' and all was light." * 



A glance at these theories of the Middle Ages shows, nevertheless, how true it is 

 that ''the dream of one age is the science of the next," for it is easy to pick out from 

 amid the debris of ruined structures fore-gleams of almost every theory which has 

 appeared since Newton's time. Thus Leonardo da Vinci, in whom the highest attri- 

 butes of the philosopher and artist were united in such a remarkable degree, regarded 

 the azure as an optical illusion, or at least as subjective. Honoratus Fabri claimed 

 that the color of the sky was due to reflexion from particles floating in the air, and 

 this at a time when the existence of the atmosphere as we now know it had not been 

 established. Fromond, and later, Funccius,^ who wrote an entire work upon this 

 subject, derived the color of the sky from a mixture of "much darkness and little 

 light," and this opinion was long the ruling one. Otto von Guericke,* also, whose 

 invention of the air-pump did much to further positive knowledge of the atmos- 

 phere, contended that black and white really give blue by mixture; and he described 

 in evidence a variety of curious phenomena which the science of that day was not in 

 position to explain. 



At last these centuries of fruitless floundering in the dark came to an end. New- 

 ton's analysis of the sunbeam with the prism furnished the needed foundation for 

 consistent theories in chromatics, and the problem of the color of the sky at once 

 resolved itself into that of the action of the atmosi^here upon the sunlight penetrat- 

 ing it. His method and its results alike are now the property of every schoolboy, 



' Sir David Brewster's Life of Sir Isaac Newton, p. 309. 



-See Fischer; Geschichte der Physik. Vol. II, p. 149. 



^ \'on (iuericke; Nova Experiment. Magdeb. Lib. IV, caj). XII, p. 147. 



