ON RAINBOWS. 659 



Fig. 19 is a specimen of the best sort of shoe made for children, 

 but, worn too short and too tight, it will become a means of harm to 

 the tender foot of the child. 



It is hard to understand how men and women can endure to wear 

 the present style of pointed-toed shoes and boots. The " corn-crop " 

 is one that never fails, and the prevalent fashion will certainly assure 

 a yield of unusual abundance. The devotee who wore peas in his shoes 

 for penance could make ample atonement for all his sins by simply 

 dressing his feet according to the mode. 



The whole subject is worthy of the profound study of the physi- 

 cian, the shoemaker, and the shoe-wearer, all of whom seem to have 

 wickedly neglected it. If men and women, in this period of the revival 

 of the antique, will study the natural and beautiful feet of that era, 

 when the appreciation of physical beauty was most perfectly devel- 

 oped, we may hope for some not-far-distant time when our demand 

 will be for a normal healthy foot in a natural and comfortable cover- 

 ing, and not for a crippled and distorted, withered, ugly " club," bound 

 in an instrument of torment. 



ON EAINBOWS.* 



By JOHN TYNDALL, F.E.S. 



TIIE oldest historic reference to the rainbow is known to all : " I 

 do set my bow in the cloud, and it shall be for a token of a cove- 

 nant between me and the earth. . . . And the bow shall be in the 

 cloud ; and I shall look upon it, that I may remember the everlasting 

 covenant between God and every living creature of all flesh that is 

 upon the earth." To the sublime conceptions of the theologian suc- 

 ceeded the desire for exact knowledge characteristic of the man of 

 science. Whatever its ultimate cause might have been, the proximate 

 cause of the rainbow was physical, and the aim of science was to ac- 

 count for the bow on physical principles. Progress toward this con- 

 summation was very slow. Slowly the ancients mastered the princi- 

 ples of reflection. Still more slowly were the laws of refraction dug 

 from the quarries in which Nature had imbedded them. I use this 

 language because the laws were incorporate in Nature before they were 

 discovered by man. Until the time of Alhazan, an Arabian mathe- 

 matician, who lived at the beginning of the twelfth century, the views 

 entertained regarding refraction were utterly vague and incorrect. 

 After Alhazan came Roger Bacon and Vitellio,f who made and re- 



* From author's advance sheets. 



f Whewell (" History of the Inductive Sciences," vol. i, p. 845) describes Vitellio as a 

 Pole. His mother was a Pole; but Poggendorff ("Handwortcrbuch d. Exacten Wissen- 

 Bchaften") claims Vitellio himself as a German, bom in Thuringen. "Vitellio" is de- 

 scribed as a corruption of Witelo. 



