Polytechnic Associatiox. (343 



carbon between the poles of the battery. It may be a question 

 whether going through the solid form does not detract from the 

 luminosity. 



The President — It is more probable that there is a transmission 

 of fine particles of carbon from one pencil of carbon to the other at 

 the rate which produces not only luminous vibrations, but also those 

 longer waves, moving at a less rapid rate, which produce heat. 



Dr. Yan der Weyde — In the galvanic battery electricity is trans- 

 formed into heat. The neutralization of two opposite electricities 

 always develops heat or light, when there is a medium which resists 

 the current. The heat is greater in proportion as the resistance is 

 greater. Fine platinum wire will become heated, and will become 

 luminous when the current is strong enough. Placing carbon there, 

 we get the vibrations. I think all the data confirm the theory of the 

 President. 



III. Fluorescent Solutions. 



Henry Morton, President of Stevens Institute, Iloboken, has made 

 a series of experiments from which he draws the curious conclusion 

 that all familiar fluorescent solutions, such as the tincture of turmeric, 

 of argaric, of chlorophyl, and the solution of nitrate of uranium, 

 emit light of the same color by fluorescence, namely, a blue identical 

 with that developed by acid salts of quinine. This blue, however, 

 as is well known in the case of quinine, is not of a single tint or 

 refrangibility, but yields a continuous spectrum, in which the more 

 refrangible rays predominate. Thus it seems that the molecules of 

 fluorescent bodies in solution are not capable of restricting their vibra- 

 tions to limited ranges, though the same substances in the solid state 

 may act quite differently. 



Dr. Van der Weyde — We give the name of phosphorescence to 

 luminosity which a body gives of itself. Fluorescence is that which 

 a body attains by being acted upon by a strong light. This light, 

 however, is always of more refrangible rays than that by which it is 

 produced. This action has been compared to the harmonic tones pro- 

 duced by a string when another string is sounding. 



The President — The subject of fluorescence has been very fully 

 investigated by Prof. Stokes of England. 



IY. Time Occupied in Perception and Expression. 

 Mr. T. C. Mendenhall, of Columbus, Ohio, has given, in The 

 American Journal of Science and Arts, an account of experiments 



