570 
Proceedings of the Royal Society 
Professor Jenkin called attention to experiments made by Mr 
Gott in St Pierre, and published in the Journal of the Society of 
Telegraph Engineers. Mr Gott converted two siphon recorders 
into a telephonic system by mechanically connecting the suspended 
coils with diaphragms. In this experiment the only conceivable 
mode of action was analogous to that suggested by Professor 
Graham Bell as the explanation of his telephone. This explana- 
tion, if not complete, was not, in Professor Jenkin’s opinion, 
erroneous. Professor Jenkin announced that he had, with Mr J. 
A. Ewing’s assistance, constructed one of Mr Edison’s phonographs, 
and that this instrument, like the telephone, gave a nasal intonation 
to the words spoken by it. 
Monday, 4 th March 1878. 
D. MILNE HOME, LL.D., Vice-President, in the Chair. 
The following Communications were read : — 
1. Proposed Theory of the Progressive Movement of Baro- 
metric Depressions or Storms ; being in continuation of 
the Paper read before the Society on July 5, 1875. 
By Mr Robert Tennent. 
In this paper it is not proposed to discuss in their relations to 
storms the effects of rain, of the earth’s rotation, of areas of high 
and low pressure external to the storm-area, and of the prevail- 
ing westerly winds, which are doubtless occasional factors in the 
progressive movement of storms. What it is intended to show 
here is that storms possess in themselves a self-motive power, 
by which their onward movement over the earth’s surface is deter- 
mined. 
It will tend to clearness if attention be pointed at the outset to 
two very different kinds of barometric depressions. The one which 
accompanies the true cyclones of the tropics is, on comparison 
with the height of the disturbance, of very limited extent, while 
