138 TROWBRIDGE — GASES AT HIGH TEMPERATURES. [April 4. 



SPECTRA OF GASES AT HIGH TEMPERATURES. 



BY PROF. JOHN TROWBRIDGE, OF CAMBRIDGE, MASS. 



{^Read April 4, 1902.) 



It seems to me highly appropriate that I should speak in Phila- 

 delphia, the home of Benjamin Franklin, on my researches in elec- 

 tricity, and that I should bring to the attention of scientific men 

 here for the first time some remarkable results in the science in 

 which Franklin was a pioneer. 



In the Jefferson Physical Laboratory of Harvard University 

 there is a Franklin electrical machine, which was ordered for the 

 College by Franklin when he was one of the Commissioners in 

 Paris. One can with great labor produce by means of it a thin 

 spark perhaps one inch in length. In the same laboratory I have 

 a storage battery of twenty thousand cells which, with suitable 

 transformers, will generate a spark six and one-half feet in length, 

 at a voltage of over six million. 



In this practical age, especially in America, one is immediately 

 asked, '' What is the use of this great spark? " Probably a similar 

 question was asked Franklin in regard to his smaller manifestations 

 of electricity, and I shall ask you to reflect upon the developments 

 of electricity since his time — the telegraph, the telephone, the 

 lighting of cities, the trolley, the X-rays — and answer for me. You 

 will remember, too, that Franklin, fearing ridicule, which we can 

 charitably think generally arises from lack of imagination, tried his 

 kite experiment in secret. I have not hesitated to build the largest 

 electrical plant at present in existence for the scientific study of 

 electricity, feeling sure that I could reach an unexplored field ; and 

 I hope that some of my results which I shall communicate to you 

 will be considered of scientific importance, and will show that I 

 have reached such a field. In the first place, Franklin would see 

 in a spark six feet in length a veritable flash of lightning, brought 

 out of the skies into a laboratory where it can be studied at all 

 times and under almost any imposed conditions. I have discovered 

 that these long sparks do not encounter, so to speak, any greater 

 resistance in passing through the air than sparks one inch in length. 

 The entire current used in propelling the electric cars in this city 

 can fjass along the path opened by these long sparks without suffer- 

 ing hardly an appreciable diminution. A rarified hole seems to be 



