652 



THE POPULAR SCIENCE MONTHLY. 



of high pressure, round which the isobars are very far apart ; this is 

 called an " auticyclone," because it is the opposite to a cyclone in 

 everything — wind, weather, pressure, etc. Between every two anti- 

 cyclones we find a furrow, neck, or "col" of low pressure analogous 

 to the col which forms a pass between two adjacent mountain-peaks. 

 Lastly, as marked in the lower edge of the diagram, isobars sometimes 

 run straight, so that they do not include any kind of area, but repre- 

 sent a barometric slope analogous to the sloping sides of a long hill. 

 The cyclones, secondaries, V's, and wedges are usually moving toward 

 the east at the rate of about twenty miles an hour ; but the anticy- 

 clones, on the contrary, are usually stationary for days and sometimes 

 for months together. We should also note that, though the general 

 principles of prognostics and the broad features of the weather in each 

 of these shapes of isobars are the same all over the world, the minute 

 details which we intend to give now apply to Great Britain and the 

 temperate zones only. 



We will now take the cyclone separately, and detail the kind of 

 wind and weather which is experienced in different parts of it. In 

 Fig. 2 we give a diagram on which we have written in words the 



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Fio. 2.— CxcLONE Pbognostics. 



kind of weather which would be found in every portion of a typical 

 cyclone ; arrows also show the direction of the wind relative to the 

 isobars and to the center. First let us look at the isobars. We find 

 that they are oval, and that they are not quite concentric, but the 

 center of the inner one we will call the center of the cyclone. Now 

 observe the numbers attached to the isobars ; the outer one is 30-0 

 inches (762 mm.), the inner one 29-0 inches (737 mm.). But suppose 

 the outer one was the same, but the inner one was 29"5 (755 mm.)' 



