326 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



and the sheet of molybdenite with its soldered terminal was held down 

 upon a block of wood by means of a mica covering screwed to the 

 block. A hole through the mica covering admitted the contact rod P. 

 The values recorded in Table III are plotted in Figure 5. By a refer- 

 ence to the curves or to the table it is seen that the rectification at 10 

 milliamperes is practically perfect, since the current from the molybde- 

 nite at 2.2 volts is 10 milliamperes, while the current in the opposite 

 direction at the same voltage is about .02 milliamperes. This is a 



TABLE II. 



Excess of Voltage to send Current from MoS 2 to Cu above 

 that to send current from cu to mos 2 . 



larger value of the rectified current, at practically perfect rectification, 

 than I was able to obtain with the carborundum rectifier. It was, 

 therefore, decided to recur to the attempt to obtain an oscillographic 

 record of the phenomenon with the aid of Braun's tube, as had been at- 

 tempted with only partial success in the study of carborundum. The 

 result in the present experiment is highly satisfactory. 



Oscillographic Records of Rectified Cycle. 



Method of obtaining the Oscillograms. — The Braun's tube oscillo- 

 graph was employed. A sketch of the oscillographic apparatus is given 

 in Figure 6. The Braun's tube was filled with hydrogen and was pumped 

 to the vacuum at which it has its highest sensitiveness. 11 The high- 



11 My thanks are due to Mr. E. L. Chaffee for very carefully pumping out the 

 tuhe for me, and for other valuable assistance with the oscillographs. 



