546 PASSAGES OVER THE ATLANTIC. 



Eastward ; because in the first case the mere speed of the ship to the 

 Westward often increases the rate of fall of the barometer ; whereas the 

 speed of a ship to the Eastward tends to make the barometer fall more 

 slowly than it otherwise would do, or even to rise. It is no uncommon 

 thing for steamers bound to the Eastward to have a rising barometer with 

 a Southerly wind, which rarely, if ever, occurs when steaming to the 

 Westward. Of course the barometers of sailing ship's are similarly 

 affected, but, as their speed is not generally so great as that of steamers, 

 the change is not usually to the same extent." 



The work mentioned {note, p. 545) illustrates Buys-Ballot's Law (pages 

 112 — 115). As shown in the diagram of the Winds, a permanent area of 

 high barometrical pressure, 800 or 900 miles in diameter, with the Azores 

 on its Eastern margin, forms a centre around which appear to revolve 

 smaller areas of low pressure ; these areas of low pressure form the centres 

 of the West India Cyclones, and of our Storms. In this diagram are 

 shown the routes of some areas of low barometrical pressure, around and 

 towards the Southern side of which the winds of Atlantic gales have been 

 observed to blow. These are taken from the same work of Captain 

 Toynbee. These gales do not appear to be true Revolving Storms, such as 

 the Tropical Hurricanes, for the reason that very few observations for 

 Easterly winds are recorded. It may be that these Easterly winds would 

 be found to the Northward of the ordinary tracks of ships ; but, as shown 

 in the diagram, the winds have been observed to blow around the Southern 

 side of the centre of low pressure, from the N.W., West, and S.W. 



It will be needless to dilate on the Pilot Charts of Captain Maury, or to 

 give the copious tables drawn up to illustrate the routes. These tracks 

 certainly seem to us to diverge considerably from any regularity of order 

 in different months, not exhibiting any gradual change with the seasons, 

 as might reasonably be expected, but have a general zig-zag course, at 

 variance with the generally received laws of simplicity and order which 

 natural phenomena, governing these courses, usually assume. This want 

 of an apparent general law of change is doubtless owing to the imperfec- 

 tion of the data upon which they are based. 



But as these recommendations were followed out by a great number of 

 sailing vessels, chiefly the fine clippers and passenger ships between Liver- 

 pool and New York, their voyages were discussed and tabulated by 

 Captain Maury in his last edition, and the general mean result of the best 

 six passages in each month is given in the ensuing tables. 



The computed routes, with the probable amount of fair or head winds, 

 gales, and calms, and distances required to be sailed over in each section 

 of the voyage, are omitted. The tables of actual experience which follow 

 will, it is thought, be quite sufficient to give an idea of the subject. Only 

 the mean resulta are given here, not the details from which they are 

 derived. 



