Page:Popular Science Monthly Volume 20.djvu/685

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vary much in quality according to where it is manufactured—but it will he found to answer the purpose, although probably Howard's is most to be depended on, the common carbonate being too caustic. It is believed that a large proportion of medical practitioners are still unaware of the remarkable qualities of this easily applied remedy, which recommends itself for obvious reasons.—The Practitioner.


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THE GULF STREAM AND THE PANAMA CANAL.

By JAMES GEIKIE, F.R.S.

NONE of the great "rivers of the ocean" has been so frequently and carefully studied as the Gulf Stream of the North Atlantic. Its course, its depth and breadth, its temperature, etc., have all been laboriously investigated, while its influence on the climate of North-western Europe bas formed a very fruitful subject of discussion. The origin of the stream is well known. The Caribbean Sea and the Gulf of Mexico are full-charged with the heated waters of the great equatorial current, and it is from this broad and deep reservoir that the famous Gulf Stream issues by the Straits of Florida to flow in a north-easterly direction toward the coasts of Europe. At the narrowest place in the straits the stream measures 30 statute miles in breadth and 1,950 feet in depth, but it gradually widens as it passes north until it spreads out over an enormous area. It has been perfectly well ascertained that the superficial stratum of the ocean throughout the whole vast space between the great Bank of Newfoundland and the coasts of France has a higher temperature than the normal of those latitudes, and is flowing persistently in a northerly and northeasterly direction toward the coasts of Greenland, Iceland, and Spitzbergen. It is doubtful whether all this body of heated water has passed through the Straits of Florida, and some physicists have maintained that only a very insignificant portion indeed has actually streamed out of the Gulf of Mexico. These writers have, therefore, held that a stoppage of the Gulf Stream would have only an infinitesimal effect upon the general temperature of the North Atlantic and the climate of North-western Europe. This view, however, has been completely overset by Dr. Croll, whose estimate of the enormous heating power of the Gulf Stream is now very generally accepted. According to this eminent physicist and geologist, the total quantity of heat conveyed by that current is probably equal to that of a stream 50 miles broad and 1,000 feet deep, flowing at the rate of four miles an hour, and having a mean temperature of not less than 65°—a temperature which gradually falls as the current goes north until it is cooled down to at least 40°. This estimate gives us 5,578,080,000,000 cubic feet of water per hour, and