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United States Coast And Geodetic Survey
T. C. Mendenhall, Superintendent
Physical Hydrography
THE GULF STREAM METHODS OF THE INVESTIGATION AND RESULTS OF THE RESEARCH
By John Elliott Pillsbury, Lieutenant U.S. Navy
Assistant, U.S. Coast and Geodetic Survey
APPENDIX No. 10 - REPORT FOR 1890
WASHINGTON GOVERNMENT PRINTING OFFICE
1891

Library Foreword

The Gulf Stream by John Elliott Pillsbury is one of the classic works of modern oceanography.  This work was first published as Appendix 10 of the Superintendent of the United States Coast and Geodetic Survey Report for 1890.  The first three chapters of this work were devoted to the history of the exploration and study of the Gulf Stream from the time of the early European explorers to the year 1884.  Pillsbury, a naval officer, undertook his famous studies from the Coast and Geodetic Survey Steamer BLAKE at that time and the remainder of The Gulf Stream was devoted to discussions of his instruments, methods and results.  The first three chapters are reproduced here as Pillsbury was as meticulous in his historical studies as he was in his scientific work.  These chapters provide a historical framework for the beginnings of modern physical oceanography as it includes the thoughts  of 16th and 17th Century explorers and "cosmographers," Benjamin Franklin's work on the Gulf Stream, and the studies of numerous late 18th and early 19th Century scientists. 

This work all preceded the first systematic oceanographic studies conducted by any nation, the Gulf Stream studies begun by the United States Coast Survey in 1844.  Guided by Alexander Dallas Bache, naval officers commanding Coast Survey vessels led these early oceanographic expeditions.  Bache, the second superintendent of the United States Coast Survey, set the formula for  modern integrated oceanographic cruises by directing that  physical oceanography, geological oceanography, and biological oceanography be incorporated into these pioneering cruises.  Over the next 40 years, the Coast Survey continued pursuing knowledge of this great oceanic current.  The efforts of the Coast Survey and the affiliated naval personnel associated with the early Gulf Stream studies did much to help lead the United States into the modern realm of oceanography.


INTRODUCTION

Geography, the science that gives to us a knowledge of the earth's surface, is divided into two

Coast and Geodetic Survey steamer BLAKE. In service 1874-1905. Conducted classic Gulf Stream studies under J. E. Pillsbury.

branches: first, all that pertains to the configuration, usually called geography, and second, everything relating to the natural forces acting thereon, called physical geography. These subjects are interlaced with the study of nearly every branch of human knowledge tending toward the good of the race in its struggle toward improvement. At first the pursuit of wealth by the discovery of new lands and peoples, brought about a study of the configuration of the surface, but little by little it was seen that the study also of the physical forces assisted toward this end and to the ease and comfort of mankind at large.

The Sun without doubt is the greatest factor in the support of terrestrial life, but this intense heat is tempered and governed by the elements, air and water, without which life as at present constituted on our globe would be unsupportable. The total area of the earth's surface is about 200,000,000 square miles, and of this only about one-fourth is land. The mean elevation of the land above the sea is less than 2,500 feet, while the mean depth of the ocean is probably about 12,000 feet. The total volume of the land above the sea level, therefore, is only about one twentieth of the volume of the ocean.  

The surface of the ground quickly becomes heated by the direct rays of the sun, but it also quickly radiates its heat into the air, producing an aerial current. The surface of the water, on the other hand, absorbing the sun's heat, rapidly communicates it to the adjoining stratum, and, radiation from its surface being comparatively slow, its currents transfer the heat so acquired to distant points. The tempering influence on the climate is the wind, taking the heat and moisture from this heated water and transferring it to the land. It is argued most forcibly that such a stupendous change in the climatology of the world as existed during the glacial period was caused by the precession of the equinoxes and the change in the eccentricity of the earth's orbit effecting an alteration in the great heat distributors, the ocean currents.  

To commerce and navigation the study of these currents is of the utmost value. The length of the voyage is shortened, and the chance of safety to vessel, cargo, and lives is increased. A strong wind against a current produces a dangerous sea, and, by a knowledge of the laws of the water's flow, a vessel, by a trifling change of course, may escape the danger.  

I venture to quote from a brochure on the subject of the Gulf Stream, by His Highness, Albert, Prince of Monaco. He says:  

Zoological geography may consider them [ocean currents] as highways which unite the zones of the ocean, and consequently cause the dissemination of species, and at the same time by the intensely progressive attenuation of salt and the temperature of these waters this highway facilitates the evolution of species. It is thus that the currents enter into the question so important to origins, monogenism, or polygenism.

Anthropology, for example, holds them responsible for the solution of the great problem, that of human migrations, which spread even to the distant archipelagos the different varieties of the race man, at the time when there was scarcely a discernible difference between man and beast, and he had at his disposal only rudimentary means for struggling against the brute forces of nature.

Botany and zoology ought to be interested in our researches, for the conditions of organic life in all its bearings are governed by these currents either warm or cold, which give to subterranean regions a veritable climate; and it is perhaps owing to certain disturbances which have taken place in the volume, direction, and temperature of these currents that the almost entire disappearance of several kinds of migratory fish is attributed, as , for example, that of the sardines, which formerly lined the coasts of France in countless numbers.

It concerns geology also, for the oceans receive a deposit, the organic and mineral detritus which the winds and waves bring to it, the stones which the glaciers wrest from the polar regions and which the icebergs carry to the temperate regions. The sea currents charge themselves with distributing all these minerals according to certain laws, and in this manner collections are formed which in later times convulsions of the earth bring to light.

Paleontology itself ought to be interested in our researches, for is it not evident that the rivers, drifting dead bodies across the continents, deposit them on sand banks far from their habitat to become the fossils of the future?

There is another reason for studying these currents which will ultimately have the most beneficial influence on mankind. It is now known that the currents vary through certain forces acting upon them, by periodic changes, entirely according to law, and again through apparently erratic forces. Probably every motion of these vast bodies is absolutely governed by laws which can be ascertained. The moisture and varying temperature of the land depends largely upon the positions of these currents in the ocean, and it is thought that when we know the laws of the latter we will, with the aid of meteorology, be able to say to the farmers hundreds of miles distant from the sea, "you will have an abnormal amount of rain during next summer," or "the winter will be cold and clear," and by these predictions they can plant a crop to suit the circumstance or provide an unusual amount of food for their stock. We will be able to say to the mariner, at such time the current will be so much an hour in such a direction, and the percentage of error will be but trifling. From a study of these great forces, then, we derive our greatest benefits, and any amount of well-directed effort to gain a complete mastery of their laws will revert directly to the good of the human race.  

In the Atlantic Ocean the currents are probably more pronounced than in either the Pacific or Indian Oceans. Without entering upon a discussion at this point as to the causes of ocean flow or of any particular current, a brief description of the main streams will not be out of place, for they are all connected more or less intimately with our own Gulf Stream. The equatorial current is usually described as being a broad band of water moving slowly across the Atlantic in the tropics. The portion situated south of the equator is divided into two parts upon meeting the resistance of Cape St. Roque, the eastern salient point of the South American coast. One branch turns to the southward toward the Antarctic, and the other is forced to the westward along the shores of Brazil and Guyana. This branch is called the Guyana coast current. The equatorial current has north of the equator an almost uninterrupted progress until it reaches the Windward Islands, but a portion of it impinges against the South American coast and perhaps increases the volume of the northern branch of the south equatorial current. At the Windward Islands all are united, and a portion of the water enters the Caribbean to assist in forming the Gulf Stream. Between the northern and southern portions of the equatorial current is the Guinea current, setting toward the east and southeast into the Gulf of Guinea. It was formerly thought to be a continuation of the North African current, "but later investigation," Findlay says, "seems to point to the fact that it is a flowing back of the waters heaped up to the westward by the prevalent winds." It seems to run strongest in the summer months, when it is felt as far west as longitude 45^o, while in the winter it reaches only as far as the twenty-third meridian. In the Northern Atlantic Ocean the Labrador current sweeps down from the Arctic along the eastern shores of Greenland and from Baffin's Bay and passes the coasts of Labrador and Newfoundland, bearing with it vast fields of ice and enormous bergs. Reaching the Gulf Stream, it is said to underrun the latter, and also in part form a counter-current to the southward along our coast as far south as Cape Hatteras, or even to Cape Canaveral.  

The Gulf Stream, the grandest and most mighty of any terrestrial phenomenon, receives its waters from the Caribbean Sea through the Straits of Yucatan. It is commonly said that a portion doubles Cape San Antonio and enters the Straits of Florida at once, while another part, after making the tour of the Gulf of Mexico, joins the first in its flow to the northward. Its waters are characterized by a deep blue color, great clearness, and high temperature. The eye can penetrate it to considerable depths, and frequently its meeting with the colder water from the polar regions can be at once distinguished.  

It is difficult for the mind to grasp the immensity of this great ocean river. The observations taken at its narrowest point were between three and four thousand in number, surface and subsurface, and a calculation of the average volume passing Cape Florida in one hour gives the enormous sum of 90,000,000,000 tons. If this one hour's water were evaporated, the remaining salt would require more than one hundred times the number of sea-going vessels now afloat in the world to carry it. That this wonderful body is governed by law in all its motions there can be no doubt. It has its daily and monthly variations in velocity, direction, and temperature, changing with as perfect regularity as the tides in a harbor. Nor do I doubt that it has also a yearly fluctuation, and perhaps others occupying a cycle of many centuries to complete.  

The Gulf Stream after leaving the Straits of Florida pursues a general northeasterly direction, pressing close to Cape Hatteras, passing between Bermuda and Nova Scotia, and as a defined and permanent stream is soon afterwards lost. Currents are found in the vicinity of the Azores Islands setting about southeast, and also on the coast of Africa setting south, which are sometimes called the southeast extension of the Gulf Stream. Warm water is found off the coasts of Ireland, Scotland, and Norway, giving evidence of a tropical flow, and this is called the northeast extension of the Stream. Whether or not these currents are wholly formed of the water issuing from the Straits of Florida remains to be discussed later.  

Man stands with bowed head in the presence of nature's visible grandeurs, such as towering mountains, precipices, or icebergs, forests of immense trees, grand rivers, or waterfalls. He realizes the force of waves that can sweep away light-houses or toss an ocean steamer about like a cork. In a vessel floating on the Gulf Stream one sees nothing of the current and knows nothing but what experience tells him; but to be anchored in its depths far out of the sight of land, and to see the mighty torrent rushing past at a speed of miles per hour, day after day and day after day, one begins to think that all the wonders of the earth combined can not equal this one river in the ocean.

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