APPENDIX. _^ 103' 



Cyclones, in the northern hemisphere, revolve round their centre from right to left, 

 ^hile those of the southern hemisphere revolve in the opposite direction. 



In the northern hemisphere these storms commence in the month of August, and cer- 

 tainly prevail in the North Atlantic till the middle of March, and there can be little 

 doubt that the same rule holds good in other parts of the same hemisphere. 



If a similar rule be applied south of tlie equator, where seasons are reversed, these 

 Btorms would then commence in February, and be occasionally experienced to the mid- 

 dle of September. 



All revolving storms move in a curvilinear course, at rates of speed varying from 

 . twenty miles an hour to ten, or even less. Those of the northern hemisphere first move 

 in a west or north-westerly direction — then northerly, curving at or near latitude 30* 

 to the north-east, and proceeding onward in that direction towards the pole. In the 

 southern hemisphere these storms obey a similar law of nature, first moving towards 

 the west and south-west, then southerly, curving in or near latitude 30* to the south 

 east, and so continuing their course to the frozen regions of the Antarctic. 



During the prevaleace of a cyclone the barometer will be found an invaluable guide. 

 This wonderfully sensitive instrument will indicate by a fall of the mercurial column 

 the moment a storm is in contact with it, and this fall will continue until the advancing 

 moiety of the storm has passed by, or over, the instrument the — mercury then begins 

 to rise, and continues to do so while the latter portion of the storm-circle is passing, 

 when it will register the original atmospheric pressure, or nearly so, except it may be in 

 the wake of the storm, where the disturbance will be great, and require a longer pericd to 

 subside. 



By carefully observing and noting the direction of the wind at the commencement 

 and termination of a cyclone, two points will be established on the circumference of tha 

 storm-circle, and a line drawn through these points will show the position of the observer, 

 from point to point as the storm swept over him. Another line drawn parallel to this 

 chord, through the centre of the circle, will show the onward direction of the storm. 



The direct speed and the diameter of a cyclone may be ascertained by noting the 

 exact time which the storm takes in passing from one known locality to another, and its 

 duration at either of these places. Thus, the cyclone which visited Turk's Island and 

 New Providence in October, 1866, was 33 hours in passing from one island to the other, 

 the distance traversed being 405 geographical miles, which is equal to a direct speed of 

 12 3-11 such miles per hour. If this rate of speed be multiplied by 16 hours, the dura' 

 tion of the cyclone at Turk's Island and at New Providence, we have 19S 4-11 geoora- 

 phical miles as the diameter of the storm at that period of its existence. In passing over 

 New Providence, the central calm of this cyclone lasted for one hour and thirty mi-' 

 nutes, which, calculated by the same rule, would make the diameter of that centre 18 2-S 

 miles. 



Should any one ask for my definition of an east or a west wind, I would answer, that 

 all winds from these points may be considered lateral deviations of the polar currents, 

 seeking, in obedience to the laws of gravitation, areas of lesser atmospheric pressure, 

 and winding in their courses for thousands of miles, sometimes in one direction, and 

 sometimes in another, like the waters of somo great river on its jonmey to the ocean. — 

 They have certainly no separate, distinct, or specific character ; and the barometer 

 heralds their approach like other winds. 



