132 POPULAR ERRORS. 



in the room were soon dead. Such a wonderful 

 discovery surely deserved to be patented. Accord- 

 ingly application for a patent was made, and in 

 September, 1871, an examiner from the United 

 States Patent Office visited General Pleasanton's 

 place in Philadelphia, inspected his experiments, 

 convinced himself of their reliability, and a United 

 States patent was forthwith granted, "for utilizing 

 the natural light of the sun through clear glass, 

 and the blue or electric solar rays transmitted 

 through blue, purple or violet colored glass, or its 

 equivalent, in the propagation and growth of plants 

 and animals." In 1876, General Pleasanton's book 

 appeared, bound in blue and printed in blue ink, 

 in which are detailed his various experiments, 

 together with a discussion on the agency of the 

 electricity, present in the blue rays, in promoting 

 life, and the testimony of many eminent persons as 

 to the value of the new discovery and accounts of 

 their success in the use of the same. The work at 

 once attracted widespread attention, not only in 

 this country but in Europe, curiosity having already 

 been excited by the publication of his earlier ex- 

 periments. In Paris the work was translated into 

 French and its experiments repeated. Blue glass 

 was introduced into conservatories and dwelling 

 houses everywhere by those eager to test the new 

 idea. 



