THE LAW OF STORMS. 9 



The path which the axis of rotation describes is not 

 inappropriately termed the "Axis Line." On the 

 " Axis Line " there is no change of wind until the . 

 center has passed, when, after a brief interval of calm, 

 the wind springs up with great fury from the opposite 

 quarter. 



It has been remarked by Piddington, " that he who 

 watches his barometer, watches his ship." This inval- 

 uable instrument, if well understood, invariably an- 

 nounces the approach of a revolving storm ; shows 

 whether the vessel is plunging into the vortex, or if 

 she be receding from it ; and hence, by carefully notic- 

 ing its indications, the disastrous consequences of a 

 hurricane may, to a great extent, be avoided, — for the 

 laws of its oscillations are very distinctly marked. The 

 barometer often stands unusually high before the com- 

 mencement of a cyclone, and frequently (if not always) 

 just around the storm. And conceiving the cyclone to 

 be divided into two parts by a diameter at right angles 

 to its path, it may be noted that the barometer always 

 falls during the passage of the advancing semi-circle of 

 a revolving storm. The barometer always rises during 

 the passage of the receding semi-circle of a revolving 

 storm. In cases of manoeuvering to take advantage of 

 the hurricane winds, and to keep just within the verge 

 of the storm, the barometer is of signal benefit, — it 

 should be kept as high as possible, without losing the 

 wind. In whatever position the ship may be, the rising 

 of the mercury announces that the first (or dangerous) 

 half of the storm has passed. 



The barometer is a faithful guide in the zone of the 

 Trade Winds. Its ordinary variations are so small that 

 any deviation from its normal height requires attention. 

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