RECORDS. 675 



SECTION OF ASTRONOMY AND PHYSICS. 

 December 4, 1899. 



Section met at 8:15 P. M., Professor M. I. Pupin, presiding. 

 The minutes of the last meeting of Section were read and ap- 

 proved. 



The following program was then offered : 



M. I. Pupin, Long Electrical Waves, with Experimental 

 Demonstrations. 



Summary of Papers. 



Professor Pupin gave a brief outline of the mathematical 

 theory of the propagation of electrical waves and exhibited ap- 

 paratus by means of which he had performed experiments bear- 

 ing upon this theory. He pointed out that the most essential 

 quantities to be considered in wave propagation are the Avave 

 length and the attenuation. The wave length plays a more im- 

 portant part in purely scientific investigations, whereas the 

 attenuation constant is of prime importance in electrical engineer- 

 ing. The difficulties met with in long distance telegraphy and 

 telephony are due to attenuation. The lecturer pointed out how 

 both of these quantities could be determined experimentally with 

 an artificial cable, which he exhibited. One of the most impor- 

 tant conclusions drawn from these experiments deals with the 

 method of decreasing the attenuation constant by increasing the 

 reactance of the line. The lecturer performed several experi- 

 ments for the purpose of illustrating the methods which he de- 

 scribed in the course of his lecture. The subject has been pub- 

 lished in full in the Transactions of the American Institute of 

 Electrical Engineers, Vol. 15, p. 1 1 1, 1899, to which reference is 

 made. 



Wm. S. Day, 



Secretary. 



