76 



your right." This roughly-stated principle will account for 

 the great storms of the Northern Hemisphere, the hurricanes 

 of the West Indies, and the typhoons of China, all circular, 

 and moving from right to left, contrary to the hands of a 

 watch ; as well as those of the Southern Hemisphere, which, 

 true to the contradictory spirit of the antipodes, have a reverse 

 circular movement. True to this law of Ballot's, a westerly 

 gale is never experienced in Ireland and in the British Isles 

 without many hours forewarning, in the fact that the pressure 

 at the north of Scotland is a half-inch less than in the south of 

 England. 



From a study of the law of rotatory storms in Europe, 

 English observers now know that cyclones go in pairs, but in 

 opposite directions, like two cog-wheels in machinery. Thus, 

 if the barometic readings in Central England be lower than 

 in Central France, then England experiences on her eastern 

 and southern coasts a true cyclone, while in France a secon- 

 dary or anti-cyclonic storm will be experienced ; the one 

 rolling round a barometric minimum, the other round the 

 barometric maximum. 



I think that observations are needed for the purpose of 

 establishing the truth of this reversion of Professor Ballot's 

 law, so that in Australia we must face the wind instead of 

 turning our backs to it, whenever the barometer will be lower 

 on our left hand than our right, though perhaps this is 

 nothing more than we should expect as the converse pro- 

 position which makes our rotatory storms follow the hands 

 of the watch from left to right, and not as in the other 

 hemisphere from right to left. We need also to register the 

 results of other observations for which our insular position, 

 and yet not distant proximity to a large continent, gives us 

 useful conditions. These are, then, the points for the scientific 

 observer to bear in mind. Can he establish, with any approach 

 to mathematical certainty, the ratio between the violence of a 

 storm and the extent of the area of barometric depression ? 

 When the area is small, do the storms follow rapidly ; and 

 when large, more slowly ? Can the rate of approach be 

 estimated by the extent of such area ? If the barometer read 

 lower at Hobart Town than at Launceston, we ought to expect 

 more sudden as well as more dangerous storms ; but if the 

 difference was observed between Hobart Town and Melbourne 

 we ought to expect them to be less rapid in their approach, but 

 to last a longer time. To a great extent, we might expect that ob- 

 servations made in England in relation to her position towards 

 the Continent, wouldbe analogous to those made in Tasmania in 

 her relation t© Australia. Whenever increased pressure occurs 

 in England yb//ow;wzy a corresponding increase of pressure on the 



