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rOPULAR SCIENCE REVIEW. 
In confirmation of these views of the effect of solar heat in 
producing a depression, I may cite an investigation by Dr. 
Hamberg, of Upsala, who has found that in July, 1872, after a 
prevalence of intensely warm weather in Southern Sweden, 
pressure gave way over the heated area ; the isobaric lines 
following the trend of the coast ; and a rotatory movement was 
thereby generated in the atmosphere above it, resulting in a 
perfectly formed cyclone which passed on over Northern Finland. 
It would appear, therefore, that the production of a cyclonic 
disturbance may be attributable to more than one agency, as all 
the theories mentioned have some facts in their favour. 
Leaving then this abstruse and imperfectly understood line 
of inquiry, let us proceed to a subject which yields us results of 
more immediate practical utility : the character and history of 
the storms when they have once started on their travels. 
I shall commence by saying that a greater mistake cannot be 
made than to assert that all storms are distinctly connected with 
cyclonic disturbances. 
The force of the wind depends on differences of atmospherical 
pressure over a given area , and the only reason why storms are 
generally associated with cyclones is that these systems afford us 
the most serious instances of disturbances of atmospheric equi- 
librium, and consequently of differences of pressure, which are 
met with on the globe. 
At any place where an area of relatively high pressure comes 
into close proximity to an area of relatively low pressure, a gale 
will result, and so a storm may be due just as much to the rise 
of the barometer in one region as to its fall in an adjacent 
district. 
For the same physical reason, however, that the eddies in a river 
extend downwards, and the water does not pile itself up in a 
peak, the normal disturbance of atmospherical equilibrium is 
the appearance of one of these vortices with pressure decreasing 
rapidly towards the centre. Wherever there is a rapid decrease 
there is a steep gradient, and consequently a strong wind. 
Defining the term cyclone, in its very widest acceptation, as 
indicating a region of diminished pressure, round and in upon 
which the air is moving along paths which are more symmetrical 
all round the centre the more perfect is the circular form of the 
system, we must at once see that not every cyclone is accom- 
panied by a storm. The fact is, that the direction and force of 
the wind are regulated by the difference of barometrical pressure 
over a given distance, and not in any way by the actual height 
of the barometer at the station at which the storm is felt, or by 
the distance of that station from the point where the barome- 
trical reading for the time being is the lowest. 
This explanation of wind motion is almost the only new 
