58 PROCEEDINGS OF THE AMERICAN ACADEMY 



No. XXVL — A PHENOMENON OF ELECTRICAL 

 CONVECTION. 



By James Jay Greexough. 



Presented June 9, 1880. 



While studying the spectra formed by passing a spark from an in- 

 duction coil through heated media, I perceived that, when the negative 

 terminal consisted of a very fine platinum wire, the passage of the 

 sparks made it glow, and soon fused it. Supposing that the heating 

 effect was due to the resistance offered by the fine platinum wire, I 

 joined the two terminals and allowed the induced current to flow 

 through the circuit uninterrupted. No heating effect was produced. 

 The phenomena is a very marked one, and the incandescence of the 

 platinum gives a brilliant star of light. 



This effect seems to be due to the impact of the particles of matter 

 upon the negative terminal, and is related to the electrical convection 

 effects first studied by Prof. Rowland. It can also be termed a 

 Crookes effect under ordinary atmospheric pressure, for the electrified 

 stream of molecules urged with great energy, rebound from the point 

 of the negative terminal, and, being confined by the stratum of gases, 

 expend their vis viva in repeated blows upon the terminal, which is 

 raised thereby to incandescence. 



No. XXVIL — THE EARTH AS A CONDUCTOR OF 

 ELECTRICITY. 



By Johx Trowbridge. 



Presented June 9, 1880. 



The Observatory of Harvard University transmits time signals from 

 Cambridge to Boston, a distance of four miles. The regular recur- 

 rence of the beats of the clock at the Observatory affords a good 

 means of studying the spreading of the electrical current from the ter- 

 minal of the battery, which is grounded at the Observatory ; and the 

 establishment of the telephone dispatch companies in Boston and 

 Cambridge, with their various ground connections, gave me unusual 

 means of studying this spreading. 



In all the telephone circuits between Boston and Cambridge, and 



