350 THE PHYSICAL CONDITION OF THE OCEAN. 



miles iu wliicli there are only seven soundings, wliile in a long strip 

 crossing the whole North Pacific, which has an area of 1*,800,()00 square 

 miles, there is no sounding at all. Nevertheless, while the approximate 

 mean depth I am mentioning may be considerably altered as knowledge 

 increases, we know enough to say that the Pacific is generally deeper 

 than the other oceans. The immensity, both in bulk and area, of this 

 great mass of water is difficult to realize, but it may assist us when we 

 realize that the whole of the land on the globe above water level, if 

 shoveled into the Pacific, would only fill one-seventh of it. The Indian 

 Ocean, with an area of 25,000,000 square miles, has a mean depth, ac- 

 cording to Mr. Murray, of a little over 2,000 fathoms. Tliis also is esti- 

 mated from a very insufficient number of soundings. The Atlantic, by 

 far the best-sounded ocean, has an area of 31,000,000 square miles, with 

 a mean depth of about 2,200 fathoms. 



The temperature of this huge mass of water is an interesting point. 

 The temperature of the surface is most important to us, as it is largely 

 on it that the climates of the different parts of the world depend. This 

 is comparatively easy to ascertain. We know so much about it that 

 we are not likely to improve on it for many years. We are quite able 

 to understand wiiy countries iu the same latitude differ so widely in 

 their respective mean temperatures, wby fogs prevail iu certain locali- 

 ties more than others, and how it comes about that others are subject 

 to tempestuous storms. On the latter point nothing has come out 

 plainer from recent discussion than the fact that areas where great dif- 

 ferences of surface temperature of the sea prevail are those in which 

 storms are generated. It is a matter of observation that in the region 

 south of Nova Scotia and Newfoundland many of the storms which 

 travel over the Atlantic to this country have their rise. An examina- 

 tion of surface temperature shows that in this region the variations are 

 excessive, not only from the juxtaposition of the warm water of the 

 Gulf Stream and the cold water of the Arctic current flowing south- 

 ward inside of it, but in the Gulf Stream itself, which is composed of 

 streaks of warm and colder water, between which differences of as much 

 as 20° F. exist. The same conditions exist south of the Cape of Good 

 Hope, another well-known birthplace of storms. Here the Agulhas 

 current of about 70° F., diverted by the land, pours into the mass of 

 water to the southward colder by some 25°, and the meeting place is 

 well known as most tempestuous. Southeast of the Rio de la Plata is 

 another stormy area, and here we find the same abnormal variations in 

 surface temperature. Yet another is found off the northeast coast of 

 Japan with the same conditions. These differences are brought about 

 by the mingling of water carried either by the flowing of a powerful cur- 

 rent turned by the land into a mass of water of different temi)erature, 

 as is the case off the Cape of Good Hope, or by the uprising of lower 

 strata of cooler water through a shallow surface stream, as appears to 

 be the case in the Gulf Stream. 



