TYNDALL AND HIS AMERICAN VISIT. 509 



August 31, 1872. 



My Dear YoTJMANs: I am in the midst of my preparations here, and shall 

 have them ready so as to enable me to start in the Russia on the 28th of Sep- 

 tember. 



I shall need your friendly aid in getting my apparatus through the custom 

 house. . . . 



With regard to the lecture rooms, in all of them I must be able to lower the 

 lights promptly. Most of my experiments will be projected on a screen. 



I purpose mixing experiment and philosophy in due proportions. 



I deal with the illustrative phenomena of light: the laws of reflection and 

 refraction, analysis and synthesis, the bearing and significance of theories. Spec- 

 trum analysis and its revelations regarding the constitution of the sun. The 

 higher phenomena of optics, interference and polarization, reaction of crystals 

 upon light. The building of crystals. The extension of radiation beyond the 

 range of the eye. The identity of light and radiant heat. This is a rough sketch 

 of the subjects which will probably occupy me. I shall not know for a certainty 

 until my preparations are complete. 



Do your audiences look down upon the lecturer? 



I suppose I can borrow an air pump in New York if I need it. 



I suppose if they do not possess ice in Boston I can have a clear block sent 

 there from New York. 



Acids, of course, are to be had everywhere. 



Are they in the habit of using compressed hydrogen and oxygen in iron bottles 

 in America, and, if so, could I borrow such bottles? 



I am taking one screen with me, but I shall sometimes require two. Is such 

 a thing to be borrowed ? 



Now, like a good fellow, answer these questions within twenty-four hours, and 

 oblige Yours, ever faithfully, John Ttndall. 



And again : 



Folkestone, September 19, 1872. 



My Dear Youmans: ... I hope they have clear ice in Boston, also nitric 

 and sulphuric acid ; if not, 1 must stock myself from New York. I have written 

 a line to Dr. Draper on this point, but I should be truly thankful to you if you 

 would make this point out for me, and if the acid is not to be had at Boston send 

 there a carboy of nitric and one of sulphuric acid. 



I am quite shocked at the mass of apparatus I have collected round me. Still 

 I thought it best to take light apparatus batteries, electric lamps, and costly 

 optical apparatus with me, having just given the experiments with them here. 



Yours ever, John Tyndall. 



Prof. Tyndall arrived in October, and began his work at once 

 by giving the Lowell lectures in Boston. Then followed courses 

 in Philadelphia, Baltimore, and Washington. 



Of his Boston lectures he says : 



Boston, October 24, 1872. 



Mt Dear Youmans: The hall of the Lowell still continues crowded, but I 

 shoot above their heads sometimes. 



In fact, this is my difficulty. I do not know the scientific level of my audience. 



Still the people are most kind and attentive, and the newspapers, I believe, 

 are very civil. 



