104 EXPEDITION TO JAPAN. 



at Port Louis on the 18th the wind hung to the northward and eastward, the trades having 

 entirely failed. The weather throughout the passage was fine^ the harometer varying from 

 -/-^ 80' to 29° 95', the thermometer from 74° to 84°, the currents setting with the wind, and 

 running at ahout three-quarters of a knot per hour. 



There is no reason to douht the correctness of the opinion of Horshurgh, to the effect that 

 the hest route for a sailing ship hound from the Cape of Good Hope to Mauritius is that in 

 which nearly the whole, if not all, the easting is made hetween the parallels of 35° and 38° of 

 latitude, and the southeast trades are struck hetween the latitude of 21° and the longitude of 

 55° or 57°. This course hrings vessels well to the windward, and enahles them to fetch the 

 island of Mauritius without difficulty, provided the trade winds do not haul north of E. hy N. 

 In the passage of the Mississippi the wind actually hauled as far as N.N.E., an occurrence not 

 usual at the season, when northerly and northwesterly winds frequently prevail from Madagascar 

 toward and heyond the island of Bourhon, (or, as it is now termed, Keunion,) and Mauritius. 



The question has been agitated as to whether it is advisable for steamers to make this curve 

 in their route to Mauritius, or to steam directly from the Cape to the island, passing close round 

 Cape Aghilus. The Commodore is decidedly of the opinion that, unless the steamer be one of 

 first-rate speed, it would be ixnwise to take the direct route, in which she would have to contend 

 against a strong trade wind and its consequent current. The difference between the two routes 

 is about 240 miles, which would hardly seem to compensate for the loss occasioned by head 

 winds and currents, leaving out of consideration the advantage of the cooler and more agree- 

 able weather of the southern passage. The mail, and indeed all the European steamers, have 

 usually taken the latter route ; and the Susquehanna, which attempted the direct course, 

 although a faster steamer than the Mississippi, had a passage of seventeen days, while the 

 Mississippi, of inferior powers and speed, made the run by the other course in fifteen days. 



The Mississippi, in doubling the Cape of Good Hope in midsummer, escaped any very heavy 

 blow, although hardly a week passes without a gale from some quarter. Horshurgh remarks, 

 in regard to the weather, that " in the storms off the Cape Bank and to the eastward, the sea 

 is turbulent, and then generally accompanied with a black overcast sky ; when they are about 

 to commence, and during their continuance, numbers of albatross, petrels, and other oceanic 

 birds, are seen flying about, although in moderate weather few are perceived, for at this time 

 they rest on the surface of the sea to fish, which they cannot do in a storm." 



Nothing was observed of a remarkable character in a meteorological point of view. The 

 temperature of the air and water gave similar indications to those in corresponding northern 

 latitudes. The barometer gave due notice of all the various changes of weather, and proved of 

 great utility. There is a peculiarity in the action of this instrument in the neighborhood of the 

 Cape, and in that part of the route across the Indian Ocean as far as the Equator, of which 

 Horshurgh thus remarks : "In the vicinity of the Cape Bank, and in most parts of the 

 southern hemisphere, the mercury rises with northerly and falls with southerly winds ; these 

 latter proceeding from a warmer atmosphere are much rarefied, consequently the mercury falls 

 in the barometer, whereas northerly winds coming from the frozen regions near the pole are 

 more dense, and cause the mercury to rise. This ought to be kept in remembrance, for, when 

 the wind is from southeast," continues Horshurgh, " I have several times observed the mercury 

 to fall considerably before it changed to the north, and expected a gale, but the fall resulted 

 only from the warmer air coming in contact with and repelling the former." 



