412 
Proceedings of the Royal Society 
lessened, even though it becomes easy to arrive at a close approxi- 
mation to the curves of a place from its geographical position 
alone, before determining the curves by working them out numeri- 
cally. 
An examination of these curves by the harmonic analysis and a 
similar examination of the temperature, hygrometric, wind, mag- 
netic, and electric curves, will in all likelihood be required before 
the true theory of the diurnal barometric oscillations can be stated. 
3. On the Air dissolved in Sea-Water. By J. Y. Buchanan. 
4. Why the Barometer does not always indicate real 
Vertical Pressure: A continuation of the Paper laid before 
the Koyal Society of Edinburgh in July 1875, in which, 
in addition to several other points, this was attempted i 
to be shown. It is now more fully written out. By 
Robert Tennent. 
The barometer only indicates real pressure when the atmosphere 
is in a state of perfect rest. It may then be represented a 
existing in vertical columns, but when it moves over a resisting 
surface its lower surface currents will be greatly retarded, while 
those aloft will move comparatively free and unimpeded. In this 
state it may be represented as moving in columns inclined in the 
direction towards which it moves. The atmosphere may thus be 
conceived as being divided into a number of spheroidal concentric 
layers, each of which is possessed of a different rate of speed, and 
moves more rapidly than the one beneath it : an increasing 
amount of friction will take place betwixt the layers as they 
approach the surface where its influence is greatest. What takes 
place may be represented in this way. Let R S be the resisting 
surface, and let 
B a 
b r 
B' 

r ^ c 
b 
C' 
— 
^ T> 
l> ^ c 
D' 
— - 
jS 
A A', B B', C O', and D 13' represent different layers of air moving 
