[77:2] _Chambers's Encyclopædia._ [81:1] Pettigrew, _op. cit._, p. 132. [82:1] John Morgan Richards, _A Chronology of Medicine_. [83:1] Lord Macaulay, _The History of England_, vol. iii, p. 379. [85:1] Thomas Joseph Pettigrew, _Medical Superstitions_. [86:1] _The Lancet_, vol. ii, 1901. [88:1] _Once a Week_, vol. xv (1866), p. 219. [88:2] E. Cobham Brewer, _A Dictionary of Miracles_. [89:1] _Common-sense_, August 13, 1737. [91:1] Hon. Daines Barrington, _Observations upon the Statutes_, 1766. CHAPTER VII THE BLUE-GLASS MANIA As illustrative of the power of the imagination, the so-called blue-glass mania, which prevailed extensively in this country, affords a striking example. About the year 1868, General Augustus J. Pleasanton, of Philadelphia, made some experiments to determine whether or not rays of sunlight passing through colored glass had any therapeutic effect on animals and plants. His selection of blue glass as a medium was probably based upon the theory that the blue ray of the solar spectrum possesses superior actinic or chemical properties. Experimenting first on plants, he adopted the method of inserting panes of blue and violet glass in the roof of his grapery, and noticed as a result an apparent extraordinary rapidity and luxuriance of growth of the vines, and later a correspondingly large harvest of grapes. Encouraged by this success, he built a piggery, having a glass roof, of which one portion was fitted with panes of blue glass, and the other with ordinary transparent glass. It was claimed that the pigs kept under the former developed more rapidly than those under the latter. An Alderney bull-calf, which was very small and feeble at birth, was placed in a pen under violet glass. In twenty-four hours it was able to walk and became quite animated. By the same method a mule was reported to have been cured of obstinate rheumatism and deafness. Again, a canary-bird, which had been an exceptionally fine warbler, declined to eat or sing, and appeared to be in a feeble state of health. The bird in its cage was placed in the bath-room of its owner's dwelling, the windows of which contained colored-glass panes. It was alleged that the little creature speedily improved; its voice became sweeter and more melodious than ever, while its appetite was simply voracious.