BOTH SIDES OF THE BLUE GLASS QUESTION. 95 



To this Gen. Pleasonton replies in the New York Evening Mail as fol- 

 lows : 

 ^^To the Editor of the Scientific American : 



"In your issue for February 24, 1877, you have inserted an article en- 

 titled 'The Blue G-lass Decei^tion,' which is devoted to the facts, and their 

 explanation in pai-t mentioned in my book, recently published, entitled 

 'Blue and Sun-lights, their Influence upon Life, Diseases, etc' 



"There is nothing in my character or history which justifies in any way 

 the application of the term 'deception' to me, on any subject whatever — 

 and this term is a reflection on the character and conduct of the Commis- 

 sioner of Patents, who issued to mo the letters patent for my discoveries of 

 the. attributes of the associated Blue and Sun-lights — as it is also on the 

 character and conduct of the Commissioner of Patents of the Dominion of 

 Canada, who has issued to me similar letters patent for the same discover- 

 ies. As for the facts described in my book, the Commissioner of Patents 

 of the United States satisfied himself of the truth of my recital of them by 

 sending an exj)ert from his bureau to investigate, who, after having devoted 

 three days to their examination at my farm, made a most favorable report 

 of his investigations on the subject, without which the letters patent would 

 not have been issued. Nothing, therefore, can be truthfully said against 

 the facts as I have published them in my book. As for the explanations 

 that I have given of the causes that have produced those facts, it may be 

 proper to state that it was only after having discovered that the accepted 

 theory of physics with which I was acquainted could furnish no satisfactory 

 solution of the problem involved in my discoveries, that I devoted myself 

 to an examination of the subjects, and I have evolved the only theories 

 with which I am acquainted that will explain them. 



" Your critic has fallen into the same error that characterizes an article 

 in Crooke's London Quarterly Journal of Science, of October, 1876, in which, 

 after quoting the experiments of Prof. H. Yogel, certainly no mean author- 

 ity on the chemical action of light, who states in his Chemistry of Light 

 and Photography (p. 78), that 'recent observations have established that 

 yellow and red rays, and not the blue and violet rays, produce the greatest 

 effects on the leaves of plants,' he states that Dr. E. Hunt, in that well-known 

 work, the Poetry of Science, fully admits that 'seeds under blue glass will 

 germinate long before others exposed to ordinary daylight, whilst under the 

 yellow ray the process of germination is entirely checked,' thus contradict- 

 ing Yogel. But he resumes, 'if the experiment is continued, it will be found 

 that under the blue glass the plants grow rapidly but weakly, and that 

 instead of producing leaves and wood, they consist chiefly of stalks upon 

 which will be seen here and there some abortive attempts to form leaves. 

 When the process of germination has terminated, if the young plant is. 

 brought under the yellow light, it grows most healthfully and forms an 

 abundance of wood, the leaves having an unusually green color from the 

 formation of a large quantity of chlorophyl. Plants do not, however, pro- 



