782 Transactions of the American Institute. 



upon the strength with which the air is condensed to make the wave. 

 When you strike a bell, you not only hear the original sound but 

 many harmonic sounds above it, which the Germans call overtones. 

 So light itself may be the result of overtones generated by the lower 

 vibrations distinguished as heat-waves. 



Dr. Van der Weyde — You may have a strong luminous wave of 

 great amplitude without heat. A violet or blue ray may be very 

 strong and have no heat. 



The President — There are three different effects in the spectrum. 

 Whatever the effect is, it becomes stronger by the amplitude of the 

 wave. 



Dr. Van der Weyde — That does not agree with the experiments 

 with the solar spectrum. With a certain velocity you have heat. 

 But make your blue wave ever so intense, and you have no heat at 

 all. In heat, you have rays of all possible amplitudes and all possible 

 velocities. Commence heating a cannon ball, and when it reaches 

 a low red heat, it shows that among the waves there are some of 

 400,000,000,000, whatever their amplitude, and however many waves 

 of less velocity there may be. As the temperature rises, you pass 

 through all the colors, and finally reach a white heat, where rays of all 

 the velocities exist together. 



The President — That reminds me of a recent series of experiment!, 

 by Budde, reported in Poggendorff's journal, that the higher waves 

 of light, the violet rays in the upper part of the spectum, which are 

 supposed to have no heating power, when thrown into chlorine gas, 

 produce heat. 



Dr. Van der Weyde — It was known long ago that a mixture of 

 chlorine and of hydrogen gas will explode when exposed to the 

 violet ray. 



The President — That is true ; but that heat can be produced by 

 the higher waves of light, in certain gases, is an entirely new fact. 



Dr Van der Weyde — A substance may become fluorescent upon 

 being exposed to violet rays, and will afterwards emit red rays. 



Adjourned. 



February 2, 1872. 



i Prof. S. D. Tillman in the chair ; Robert "Weir, Esq., Secretary. 



Road Steamers. 

 Mr. J. K. Fisher read a paper describing the various carnages pro- 

 posed for the use of steam upon common roads. 



