CHAPTER XII.

CURRENTS AND WHALING.

It may at first sight appear singular that subjects apparently so dissimilar as currents and whaling should be united to form the subject of one chapter. Before its conclusion, however, we trust to establish satisfactorily that the course of the great currents of the ocean, sweeping with them the proper food of the great cetaceous animals, determines not only the places to which they are in the habit of resorting, but the seasons at which they are to be found frequenting them.

In the devious and extensive cruise performed by the Exploring Expedition, many, and perhaps greater opportunities than had before been enjoyed by any one vessel or squadron were afforded for investigating the course and direction of currents. The field of research thus opened proved to be so vast that I cannot but regret that we had not possessed still greater facilities for prosecuting the inquiry than we could attain even in a voyage of such long duration. In particular, simultaneous observations in different parts of the ocean, and their continuance for months or even for the whole year, were requisite to render the results, that I believe I have attained, more satisfactory and conclusive. Enough, however, has I hope been done to excite the curiosity and rouse the attention of future navigators, by whose labours a sufficient number of facts may be collected upon which to found a theory that will admit of no question.

To obtain the greatest practicable number of experiments with the current log, of which mention has been made in the first chapter, was an object which claimed early attention, and which was kept constantly in view throughout the cruise. I was however aware, as all

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those who have used this instrument extensively must be, that it is liable to many objections, and that in particular if the current be beneath the surface, or, for want of a better term, may be denominated submarine, no result can be obtained by its use. If not perfect, however, the current log was at least a useful indicator; and its regular use, which was ordered to take place whenever the state of the sea would permit, served to keep the subject of currents continually before us. It is unnecessary to recount the number of the experiments that were performed; suffice it to say, that they were made both by day and by night, and were persevered in until the record of them became an almost daily portion of our journals; and the interest in them was extended from the officers, until they became a subject of inquiry even among the crews.

This

Upon the chart that exhibits the tracks of the squadron when united, and of the vessels when separate, the direction and force of the upper currents is indicated. The results thus expressed were obtained by a comparison of the position assigned to the vessels by the dead reckoning, and the true place shown by astronomic observations. method, when practised by good observers, and particularly when furnished with chronometers of such excellence as can now be obtained, is in my opinion that which is liable to the fewest objections. Still it is to be desired that the allowances in the dead reckoning for lee-way, the heave of the sea, steerage, &c., should be founded on principles so certain as to admit them to be applied separately, and that less was left to the mere judgment of the navigator. The use of steam in navigation, and the introduction of improvements in the log, will probably bring about this desirable result.

In order to attain greater certainty, every calculation on which the rate and direction of a current was founded, has been made anew since the return of the Expedition; and it is trusted that the chart now exhibits a full and correct representation of the action which influenced the position of the vessels, freed in a great measure from the causes of uncertainty of which I have spoken above.

On the same chart are represented the courses of the winds, and the isothermal lines for every five degrees of the thermometer, from 30° to 95°. The zones lying between these lines are coloured in tints varying from cold to warm, in order that at a single glance the curves may be conspicuous. By simple inspection it will be seen how close is the connexion between the position of these lines and the figure of the zones they enclose, with the flow of the streams of which I am about to treat. It will at least be obvious that the distribution of the temperature at the surface of the ocean is affected by causes very

different from those which are usually considered to be the only ones in action.

In order to obtain precision of language, I have chosen to distinguish between streams and currents, employing the former term to express the movements of water by which the circulation of the great mass of the ocean is maintained, and confining the latter to those less extensive in their influence, or local in their effects; and the direction from whence the great streams are derived as polar and equatorial:

I shall now proceed to speak of the streams which we met with on our voyage, citing, whenever it is necessary, such facts derived either from general experience, or the authority of individual observers, as may be useful to extend the inferences, or verify our own observations.

Immediately after our departure from the capes of Virginia, we felt the influence of a stream setting to the southward, and parallel to the coast. The existence of this was apparent from our first observation of latitude. It may, however, often escape notice, as the navigator is apt to ascribe the effect of this stream rather to an error in taking his departure, than to a set of current. In order that the fact may be clearly perceived, it is necessary that the distance of the vessel from the lighthouse, or other object on shore with which the dead reckoning begins, should be determined by precise observations, instead of being merely estimated, as is the usual mode. Notwithstanding the inaccuracy growing out of this cause, it has been long known to seamen that a counter-current is setting close to the inner edge of the Gulf Stream, and has been distinguished by them as its eddy. That it cannot be of the nature of an eddy of that heated body of water, is evident from the great difference of temperature, which falls suddenly fifteen or twenty degrees, in passing from the Gulf Stream into that which flows in an opposite direction. The latter is also five to ten, and even fifteen degrees colder, according to the season, than the waters of our bays or rivers.

The inner stream flowing to the southwest is now well known to exist along our whole eastern coast and that of Nova Scotia, and the masters of our packet-ships have by experience discovered the value of which it may be to them in their homeward passage. This they do by keeping to the north of the forty-second parallel until off Cape Sable.

Tracing this stream in a direction opposite to its course to the most distant part of Nova Scotia, it is found to be a part of one that flows southwards along the shore of Labrador, and which is well known by the name of that country. The Labrador Stream therefore flows along the coast of the New Continent, from Davis's Straits as far to the south