THE COUESE OF STOEMS. 
145 
The irregular and somewhat interlacing lines observed upon 
the chart, represent the paths of all the centres of barometric- 
depression^ which admitted of being traced in the month of April^- 
1878. I say the paths of the centres of barometric depression,, 
because there is^ no reason to suppose that all of these centres 
were centres of actual storms. If a choice existed, one would 
have preferred a chart of all the great storms of a year to 
one of all the barometric depressions of a month, for although, as. 
I have already said, there is an essential identity of nature 
between aU depression-centres as regards the circulation of winds- 
around them, it by no means follows that the minor depressions 
can be taken as types of the major, with reference either to- 
rapidity of movement or to direction of movement. However, we 
must make the best of the material to hand* Possibly, at some 
future time, when other charts have been issued, we may have a 
further opportunity of pursuing the subject. 
Let us see, then, what the chart teaches with regard to the- 
paths of storms or of depression-centres* 
Notice first the number of these lines. There are altogether 
twenty-two, representing that number of separate depression- 
centres. There might probably be more in a winter month. 
Notice next the point of origin. That is very various. Some 
make their first appearance on the Pacific coast of America,, 
others on the Atlantic coast. Some commence their career at 
sea, others on land. Several appear to take their origin in the 
Arctic regions* 
The direction in which the centres move is a point of 
special interest. As a rule, and speaking generally, they all 
move from West to East, but the deviations from a straight, 
course are numerous and large. A common tendency is to take 
a South-East course at first, and afterwards a North-East course,, 
the result being a curved line with its concavity towards the 
North. 
