effects of articulate speech, while I uttered the sentence, 

 'Do you understand what I say?' into the telephone 

 placed in the lecture hall. To my delight an answer 

 was returned through the instrument itself, articulate 

 sounds proceeded from the steel spring attached to the 

 membrane, and I heard the sentence, 'Yes, I under- 

 stand you perfectly.' It is a mistake, however, to sup- 

 pose that the articulation was by any means perfect, 

 and expectancy no doubt had a great deal to do with 

 my recognition of the sentence; still, the articulation 

 was there, and I recognized the fact that the indistinct- 

 ness was entirely due to the imperfection of the instru- 

 ment. I will not trouble you by detailing the various 

 stages through which the apparatus passed, but shall 

 merely say that after a time I produced a form of in- 

 strument, which served very well as a receiving telephone. 

 In this condition my invention was exhibited at the Cen- 

 tennial Exhibition in Philadelphia." 



BELL VERSUS GRAY 



Reference is made in this quotation from Professor 

 Bell's paper to "intermittent," "pulsatory," and 

 "undulatory" currents and the difference in the nature 

 of these currents, and an appreciation of these differ- 

 ences is very important in understanding the working 

 of the speaking telephone. It was an important feature 

 of the controversy between Bell and Gray in settling the 

 question of priority in the invention of the telephone. 

 As explained by Bell, intermittent currents are those 

 interrupted to produce sounds quite instantaneous; 



VOL. VIII. 6 [ 8l ] 



