GEOGRAPHY AND ANTIQUITIES.

ON THE PROGRESS OF THE SURVEY OF THE COAST OF THE
UNITED STATES.

AT the recent meeting of the American Association, Prof. A. D. Bache, the Superintendent of the Coast Survey, gave an account of its progress. "The survey of the coast was first proposed by Mr. Jefferson, in 1807. Congress acted upon the subject but tardily. The Executive was even more tardy after the law had been passed. At that time the importance of the work was hardly understood. The work was greatly in advance of the times. Mr. Gallatin sketched the plan of a magnificent geodetic work; one which, embracing the survey of the coast of the United States, should connect with it a survey on the water of all the approaches to that coast.

"In 1816 the work was commenced, under the direction of Mr. Hassler; but in 1818, from the idea that he was proceeding too slowly, the work was stopped. It was revived in 1832, and he seemed then to have more enlarged ideas of what the work might be made, for his second series of observations were on a larger scale than the first. His instruments for measuring horizontal angles are even now quite as good as any used abroad. In 1844, when he was proceeding rapidly, his labors were closed by death. The year 1844 was with me a year of observation. I examined the complaints of the slowness with which the works were going on, and concluded that, if it was to be pushed much more rapidly, more money must be granted. Still, I thought the work might be in some way or other expedited, as I had the advantage of beginning with a foundation already laid, and with trained assistants. Mr. Hassler intended to begin at New York, and extend the work north and south from that point, working at both ends. I concluded to divide this into smaller sections, so that we might extend the work from several centres. The question of the manner of making the division depended upon the then progress of the work itself, and the manner of operation. The plan of operations in the coast survey is briefly this:-First, a base line is measured by the most accurate means we can devise; say a line of from 6 to 10 miles in length. We have some bases as small as 6 miles; and we

have one upwards of 10 miles in length. Having established the length of this base, a series of triangles is adopted, of gradually increasing sides, the lengths of which, or distances between the angular points, are known from the base and measured angles. By measuring the angles from the extremities of the base, the length of which is exactly known, we obtain the direction and distance of a new point, and thus a new base line. That line, in turn, establishes another at a still greater distance; and thus the surface of the earth is covered with a network of triangles, each side of each triangle being calculable from the measure of the angles, and from the length of the originally determined base. This would be easy, were the triangulation upon a plain surface; but the calculation is not so simple as it would at first appear. The earth must be considered, in computing these large triangles, not merely as a sphere, but as a spheroid. Next comes the astronomical part of the survey. The direction of the lines with reference to the meridian must be known. The latitude of the points must be ascertained, and their longitude must be determined. Having these data, we then know from computation the latitude and longitude of any point, and the angle with the meridian of any line connected with the triangulation. This is the second part of the work.

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"We have thus a great scheme, in which the progress may be very rapid, because the steps may be very great. You may have-as we have in some cases in our New England triangles—a side of 60, 90, or even 100 miles in extent; and thus you may make vast strides along the coast at once, by taking advantage of hills properly situated in the interior of the country and overlooking the ocean shore. Haying determined these points with great nicety, with large instruments, and a great deal of care, the work between them need not be done so elaborately. New points are determined between the former, upon the same great system of triangulations, called the secondary triangulations. Upon this, with a still less exact mode of working,-namely, with the plane table, the topography is laid down so far as it may be necessary to show the coast to the navigator, and for purposes of defence. All the points are checked by the secondary triangulations, which in their turn are checked by the primary; so that, having taken great pains in the first part of the work, you cannot wander far out of the way in the second part, or in the topography. Having thus determined the outline of the coast, the hydrography gives you a picture of the sea, just such as the topography gives you of the land above its surface, and this completes the survey.

"Originally, I divided the survey into eight sections. Texas made a ninth, and Oregon adds a tenth section. In the first section, from Point Judith to the boundary, we have now finished the primary triangulations, from the base on the Boston and Providence Railroad, along the coast of Rhode Island, Massachusetts, and New Hampshire, into Maine. The hills of New England seem as if they had been made for triangulation. They are so situated that we can pass rapidly along the coast with long strides; and the only difficulty is to avoid being tempted to make the lines too long. I have frequently, however, in taking such long lines, taken also an intermediate shorter line, for the

purpose of verification. We have then passed, in five years, on the primary triangulation, from Rhode Island to Maine; and it could have been done in three years, had it been desirable so to occupy the time. "The secondary triangulation has extended along the coast, determining the positions of points near the coast, around the peninsula of Cape Cod to Cape Ann. There are now two parties at work upon this step in the process; one passing from Cape Ann to Newburyport, and the other from Newburyport to Portsmouth; so that by the end of the season we shall have reached nearly to Saco, in Maine, with our secondary triangulation.

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The topography has been carried regularly forward in the same way, with but one exception, in which I have perhaps taken some responsibility. I certainly did have Boston Harbor surveyed two years before it would have been done in the regular course. But then I had a very violent motive for this; namely, an appropriation made by the State of Massachusetts to hasten the survey of the coast,-an act of liberality which has never been imitated by any other State in the Union. We have two large manuscript maps of Boston Harbor, which you will see in the State-House, in the month of October next, of a very finished character. Thus, in six years (adding the present year), at this end of the work, we have advanced from Point Judith, with the primary triangulation, to Portland; with the secondary, beyond Portsmouth; and with the topography, to Gloucester.

"The hydrographers have had a long and difficult piece of work in this section. They have had those famous Nantucket Shoals to stop them. But if the survey had rendered no other benefit to the country than making known the before unknown and hidden dangers of that part of the coast, it certainly would have repaid to the country, in money, the whole amount which it has cost. One vessel which came very near stranding upon shoals-now, through the enterprise of Lieut. Davis, made known and familiar to us-had a cargo which paid the government a duty of $125,000; and if this sum had been devoted to the survey, the shoal would have been discovered years ago. Lieut. Davis's discoveries consist of an important shoal outside of the Old South Shoal of Nantucket, lying right in the track of vessels from New York to Europe, and returning, and of vessels passing from the New England States to the Southern States and South America. The hydrography has been extended up Buzzard's Bay through Nantucket Sound, through the Vineyard Sound, has embraced the Nantucket Shoals, and has included the hydrography of Boston Harbor, of which an accurate chart has been made. The results of the survey pass through a regular process, from the time the observations are made in the field to the time the map is produced in the office. The assistants, who make the observations, report them, and compute them. Other computers also pass over the same calculations. The results are brought into juxtaposition and compared. If they agree, they are considered as correct. If they disagree, the canse is carefully examined, and the error corrected. The results, thus verified, are placed upon paper in the ordinary forms of projection of maps. They are next engraved, as fast as we can find hands

to engrave them; and when engraved they are made public. We have published, within the five years past, twenty-five sheets of maps of a very finished kind. They have been examined by our own citizens, and by foreigners; and I believe with approval in every case. I have carefully compared them with foreign maps, in order to see where we stood, and what we had to learn. The arrangements for this part of the work are not now quite adequate to the demand of the fieldwork. The number of computers, draughtsmen, and engravers requires to be increased. It is almost impossible to get a good map-engraver to come to Washington, as all are employed at home.

"It is easy to see when the first section of the work may be finished. There are about sixteen stations to the boundary, which could be occupied in two years and a half, at the present rate, making the astronomical observations as well as the geodetic. I do not propose to do so, because my time in the spring and autumn is better employed in other positions, and it would be better, therefore, to occupy two stations in the north in a year, than to occupy six or eight, as I have done when it was necessary, in order to get ahead of the other operations of the survey. So much for the first section.

"The second section is done, excepting the work of verification and making necessary changes. There was a rich harvest of hydrography in Long Island Sound,-discoveries of detached rocks, about which little had been said. But in the case of the entrance to New York Harbor, there was a richer harvest; for there Capt. Gedney found a new channel, now called by his name. This was either a new channel, or a channel which has long existed, but which was newly discovered; most probably the latter, and that in the progress of the hydrography of the coast survey. The advantages of a channel having two feet more of water in it than the main ship-channel will be appreciated by all. Buoys have been placed in it, and it is easy to find the way out and in.

"I was told last year that it was filling up; which is not true. It is often remarked, that the coast is changing every year, and there is, therefore, little use of surveying it. The truth is, that there are a few points in which the coast is really changing, and those points should be carefully watched. We should know where they are, and why they are changing, and how to stop the changes if it is necessary, and how to avail ourselves of them if it is necessary. But in New York Harbor it was the easiest thing in the world, at a trifling cost, to have the hydrography repeated, and the result showed that there are not six inches more or less of water than there were when the survey was made, so that the changes which have taken place in the harbor, if any, are exceedingly slight. And if we consider the nature of the operation of sounding, I should say that there had been probably no change.

"The discovery or determination of three channels in Delaware Bay rewarded the exertions of the officers engaged there,-Capt. Gedney and Lieut. Davis. These channels are not of so much interest as the channel into New York Harbor; but they are of very great importance. One of them is now constantly used by vessels

carrying coal from Philadelphia to the eastern parts of the Union; buoys having been placed in it, so that it is known. Another one enables vessels to pass directly across to the breakwater, when lying in Cape May Roads, the wind comes out at northwest, exposing them to the dangers of a lee-shore. This section of the work (the second), then, I consider as completed, with the exception of a portion of the work of verification.

"Mr. Hassler did not at once publish his results, and I have aimed to bring up all the back-work, and then to keep the publication abreast of the work itself. This I have nearly been able to effect. The third section extends from the capes of the Delaware to the capes of the Chesapeake, and includes the States of Maryland, Virginia, and a part of Delaware. The primary triangulation has been carried down the Chesapeake into Virginia, and I have very little doubt, from the report of the assistant who had charge of that part of the work, that the triangulations will, this season, reach the James River. The secondary triangulation already extends, both in the Chesapeake Bay and on the ocean shores, into Virginia. The fourth section embraces the State of North Carolina. The primary triangulation has been carried, from the base measured on Bodies Island, up the Albemarle Sound, into Pamlico Sound, and the sheet of water which, under the various names of Roanoke Sound, Currituck Sound, &c., fills the space between the sandy part of the coast of North Carolina and the swamp which immediately joins it, those sounds constituting the great line of communication between the North and South, through the Dismal Swamp Canal from the Chesapeake Bay into Albemarle Sound.

"It is very remarkable that natural causes should tend to counteract natural difficulties. Such a change in the direction of the currents has taken place near Cape Hatteras since 1846, that the point of the cape has begun to make out, and thus affords a natural protection, behind which there is a beautiful cove, easy of entrance, with a capital anchorage, and perfectly protected from the sea in a northeast wind. Hatteras Inlet affords a beautiful harbor of refuge to the extensive coasting trade passing from the South to the North, and from the North to the South, in the United States. Now we can only approximately estimate when this section will be done. The reconnoissance was only made in 1843, and the triangulation commenced in 1845. But the period of survey, from the beginning to the end, cannot exceed twelve years, and three of these have passed.

"The next section is a very interesting one, along the coast of South Carolina and Georgia. It is a curious, but a uniform fact, that the coast of the United States in general lends itself to this kind of work. Where it is not made up of the bluffs which we have in New Eng land, with the noble hills in the interior, there is generally a sandy island or a continuous beach of sand, or a hillock, or a piece of morass within which there is very deep water, forming an internal navigation, and across which the lines are readily run, affording an opportunity exactly for this work. What could be better than Albemarle and Pamlico Sound on the flat coast of North Carolina? In South