BOTH SIDES OF THE BLUE GLASS QUESTION. 93 



carbon in animals and its absorption in plants than any others in the spec- 

 trum, the violet rays having least power in these respects, with the excejD- 

 tion of the red rays in the case of animals. The absorption of carbonic 

 acid by plants, and its evolution by animals, we hardly need add, are prime 

 essentials to the growth and health of each. The notion that light posses- 

 ses a magnetizing power on steel was upset by Niepce de St. Victor, in 1861. 

 After removing every source of error, he 'found it impossible to make one 

 sewing needle, solarized for a very long time under the rays of light con- 

 centrated by a strong lens, attract another suspended by a hair, whether 

 the light was white or colored by being made to pass through a violet-col- 

 ored glass.' 



"We can proceed further and even show that violet light is in some re- 

 spects hurtful to plants. Cailletet for example says, in 1868, that 'light 

 which was passed through a solution of iodine in carbonic disulphide pre- 

 vents decomposition altogether.' Baudrimont says that 'no colored light 

 permits vegetables to go through all the phases of their evolutions. Yiolet- 

 colored light is positively injurious to plants; they absolutely require white 

 light.' This scientist instituted the most elaborate experiments on the sub- 

 ject, ranging over eleven years, from 1850 to 1861; and the result of all his 

 labor may be summed up in the simple statement that no illumination which 

 human ingenuity can devise is so well adapted for promoting natural pro- 

 cesses as the pure white light provided by the Creator. So much by waj- 

 of general denial of the claims of superior efficacy residing in blue light of 

 any kind. 



"The spectroscope has clearly demonstrated that the violet glass acts 

 purely as a shade for decreasing the intensity of the solar light. And in 

 the simple fact that it does so serve as a shade lies the sole virtue (if anr 

 there be) of the glass. In 1856, Dr. Daubeny made experiments on the ger- 

 mination of seeds, and in his report is this suggestive sentence: 'In a south 

 aspect, indeed, light which had passed through the ammonia sulphate of 

 copper (blue solution), and even darkness itself, seemed more favorable 

 than the whole of the spectrum; but this law did not seem to extend to the 

 case of seeds placed in a northern aspect where the total amount of lio-ht 

 was less considerable.' 



"We now propose to finish our discussion by examining into the effects 

 of light and darkness upon organisms. And we may especially here recall 

 the fact that Gen. Pleasonton claims that not only does the blue light stim- 

 ulate growth, but that it is a positive remedial agent for such severe ail- 

 ments as spinal meningitis, nervous irritation and exhaustion, rheumatism, 

 hemorrhage of the lungs, deafness, partial paralysis, shock due to severe 

 contusion, and others, of all of which he cites cases. 



"The theorj^that various colored lights exercise different effects on the 

 human system is an old one. In 1831, Dr. JSTewbery of this city asserted 

 that yellow light stimulates the nervous, pink the nutritive and blue the 

 locomotive temperament; and recently Dr. Ponza, an Italian physician, has 



