622 
Proceedings of the Royal Society 
PRIVATE BUSINESS. 
Mr J. A. Dixon, Professor D. H. Marshall, Professor C. Michie 
Smith, and Mr Josiah Livingston, were balloted for and declared 
duly elected Fellows of the Society. 
Monday , Vjth April 1882. 
The Kev. W. LINDSAY ALEXANDER, D.D., 
Vice-President, in the Chair. 
The following Communications were read : — 
1. On the Definite Article in Greek, with special reference 
to the Revised Version of the New Testament By 
Professor Blackie. 
2. On the Action of the Microphone. By Professor James 
Blyth, M.A. 
In the microphone transmitter, as usually employed in circuit 
with a battery and a Bell telephone, we have essentially two pieces 
of carbon resting lightly against each other, through which the 
current passes. That the instrument may work effectively two 
things are requisite,- — first, that the carbons be always in contact, or 
at least sufficiently near for the current to pass between them; and, 
secondly, that they be not pressed together so tightly as to prevent 
any motion of the one relatively to the other. This state of things 
is sufficiently well described by the term “ loose contact,” first used, 
I believe, by Professor Stokes. 
To understand the action of the mici^hone, we have to find 
out what effects are taking place at the loose contact when the 
instrument is acted upon by sonorous waves. These are twofold,- — 
first, the effect produced by the sound waves (that is, the variation 
of density due to the condensations and rarefactions of the air) 
which pass directly through the air when they arrive at the loose 
contact ; and, secondly, the effect produced by tremors set up in the 
