On the tide waters the State will have little to do. Some time before the war, Congress authorized the Executive to have an accurate survey made of the whole sea-coast of the United States, comprehending, as well as I remember, the principal bays and harbors. A Mr. Hassler, a mathematician of the first order from Geneva, was engaged in the execution, and was sent to England to procure proper instruments. He has lately returned with such a set as never before crossed the Atlantic, and is scarcely possessed by any nation on the continent of Europe. We shall be furnished, then, by the General Government, with a better survey than we can make, of our sea-coast, Chesapeake Bay, probably the Potomac, to the Navy Yard at Washington, and possibly of James' River to Norfolk, and York River to Yorktown. I am not, however, able to say that these, or what other, are the precise limits of their intentions. The Secretary of the Treasury would probably inform us. Above these limits, whatever they are, the surveys and soundings will belong to the present undertaking of the State; and if Mr. Hassler has time, before he commences his general work, to execute this for us, with the use of the instruments of the United States, it is impossible we can put it into any train of execution equally good; and any compensation he may require, will be less than it would cost to purchase instruments of our own, and have the work imperfectly done by a less able hand. If we are to do it ourselves, I acknowledge myself too little familiar with the methods of surveying a coast and taking soundings, to offer anything on the subject approved by practice. I will pass on, therefore, to the general survey of the Rivers above the tide waters, the Mountains, and the external Boundaries.
I. Rivers.—I have already proposed that the general survey shall comprehend these from the tide waters as far as they are navigable only, and here we shall find one-half of the work already done, and as ably as we may expect to do it. In the great controversy between the Lords Baltimore and Fairfax, between whose territories the Potomac, from its mouth to its source, was the chartered boundary, the question was which branch, from Harper's ferry upwards, was to be considered as the Potomac? Two able mathematicians, therefore, were brought over from England at the expense of the parties, and under the sanction of the sentence pronounced between them, to survey the two branches, and ascertain which was to be considered as the main stream. Lord Fairfax took advantage of their being here to get a correct survey by them of his whole territory, which was bounded by the Potomac, the Rappahanoc, as was believed, in the most accurate manner. Their survey was doubtless filed and recorded in Lord Fairfax's office, and I presume it still exists among his land papers. He furnished a copy of that survey to Colonel Fry and my father, who entered it, on a reduced scale, into their map, as far as latitudes and admeasurements accurately horizontal could produce exactness. I expect this survey is to be relied on. But it is lawful to doubt whether its longitudes may not need verification; because at that day the corrections had not been made in the lunar tables, which have since introduced the method of ascertaining the longitude by the lunar distances; and that by Jupiter's satellites was impracticable in ambulatory survey. The most we can count on is, that they may have employed some sufficient means to ascertain the longitude of the first source of the Potomac, the meridian of which was to be Lord Baltimore's boundary. The longitudes, therefore, should be verified and corrected, if necessary, and this will belong to the Astronomical survey.
The other rivers only, then, from their tide waters up as far as navigable, remain for this operator, and on them the same objects should be noted as proposed in the county surveys; and, in addition, their breadth at remarkable parts, such as the confluence of other streams, falls, and ferries, the soundings of their main channels, bars, rapids, and principal sluices through their falls, their current at various places, and, if it can be done without more cost than advantage, their fall between certain stations.
II. Mountains.—I suppose the law contemplates, in the general survey, only the principal continued ridges, and such insulated mountains as being correctly ascertained in their position, and visible from many and distant places, may, by their bearings, be useful correctives for all the surveys, and especially for those of the counties. Of the continued ridges, the Alleghany, North Mountain, and Blue Ridge, are principal; ridges of partial lengths may be left to designation in the county surveys. Of insulated mountains, there are the Peaks of Otter, in Bedford, which I believe may be seen from about twenty counties; Willis' Mountains, in Buckingham, which from their detached situation, and so far below all other mountains, may be seen over a great space of country; Peters' Mountain, in Albemarle, which, from its eminence above all others of the south-west ridge, may be seen to a great distance, probably to Willis' Mountain, and with that and the Peaks of Otter, furnishes a very extensive triangle; and doubtless there are many unknown to me, which, being truly located, offer valuable indications and correctives for the county surveys. For example, the sharp peak of Otter being precisely fixed in position by its longitude and latitude, a simple observation of latitude taken at any place from which that peak is visible, and an observation of the angle it makes with the meridian of the place, furnish a right-angled spherical triangle, of which the portion of meridian intercepted between the latitudes of the place and peak, will be on one side. With this and the given angles, the other side, constituting the difference of longitude, may be calculated, and thus by a correct position of these commanding points, that of every place from which any one of them is visible, may, by observations of latitude and bearing, be ascertained in longitude also. If two such objects be visible from the same place, it will afford, by another triangle, a double correction.
The gaps in the continued ridges, ascribed to the general surveyor, are required by the law to be noted; and so also are their heights. This must certainly be understood with some limitation, as the height of every knob in these ridges could never be desired. Probably the law contemplated only the eminent mountains in each ridge, such as would be conspicuous objects of observation to the country at great distances, and would offer the same advantages as the insulated mountains. Such eminences in the Blue Ridge will be more extensively useful than those of the more western ridges. The height of gaps also, over which roads pass, were probably in view.
But how are these heights to be taken, and from what base? I suppose from the plain on which they stand. But it is difficult to ascertain the precise horizontal line of that plain, or to say where the ascent above the general face of the country begins. Where there is a river or other considerable stream, or extensive meadow plains near the foot of a mountain, which is much the case in the valleys dividing the western ridges, I suppose that may be fairly considered in the level of its base, in the intendment of the law. Where there is no such term of commencement, the surveyor must judge, as well as he can from his view, what point is in the general level of the adjacent country. How are these heights to be taken, and with what instrument? Where a good base can be found, the geometrical admeasurement is the most satisfactory. For this, a theodolite must be provided of the most perfect construction, by Ramsden, Troughton if possible; and for horizontal angles it will be the better of two telescopes. But such bases are rarely to be found. When none such, the height may still be measured geometrically, by ascending or descending the mountain with the theodolite, measuring its face from station to station, noting its inclination between these stations, and the hypothenusal difference of that inclination, as indicated on the vertical arc of the theodolite. The sum of the perpendiculars corresponding with the hypothenusal measures, is the height of the mountain. But a barometrical admeasurement is preferable to this; since the late improvements in the theory, they are to be depended on nearly as much as the geometrical, and are much more convenient and expeditious. The barometer should have a sliding nonius, and a thermometer annexed, with a screw at the bottom to force up the column of mercury solidly. Without this precaution they cannot be transported at all; and even with it they are in danger from every severe jolt. They go more safely on a baggage-horse than in a carriage. The heights should be measured on both sides, to show the rise of the country at every ridge.
Observations of longitude and latitude should be taken by the surveyor at all confluences of considerable streams, and on all mountains of which he measures the heights, whether insulated or in ridges; for this purpose, he should be furnished with a good Hadley's circle of Borda's construction, with three limbs of nonius indexes; if not to be had, a sextant of brass, and of the best construction, may do, and a chronometer; to these is to be added a Gunter's chain, with some appendix for plumbing the chain.
III. The External Boundaries of the State, to-wit: Northern, Eastern, Southern and Western. The Northern boundary consists of, 1st, the Potomac; 2d, a meridian from its source to Mason & Dixon's line; 3d, a continuation of that line to the meridian of the north-western corner of Pennsylvania, and 4th, of that meridian to its intersection with the Ohio. 1st. The Potomac is supposed, as before mentioned, to be surveyed to our hand. 2d, The meridian, from its source to Mason & Dixon's line, was, I believe, surveyed by them when they run the dividing line between Lord Baltimore and Penn. I presume it can be had from either Annapolis or Philadelphia, and I think there is a copy of it, which I got from Dr. Smith, in an atlas of the library of Congress. Nothing better can be done by us. 3d. The continuation of Mason & Dixon's line and the meridian from its termination to the Ohio, was done by Mr. Rittenhouse and others, and copies of their work are doubtless in our offices as well as in those of Pennsylvania. What has been done by Rittenhouse can be better done by no one.
The Eastern boundary being the sea-coast, we have before presumed will be surveyed by the general government.
The Southern boundary. This has been extended and marked in different parts in the chartered latitude of 36° 31´ by three different sets of Commissioners. The eastern part by Dr. Byrd and other commissioners from Virginia and North Carolina: the middle by Fry and Jefferson from Virginia, and Churton and others from North Carolina; and the western by Dr. Walker and Daniel Smith, now of Tennessee. Whether Byrd's survey now exists, I do not know. His journal is still in possession of some one of the Westover family, and it would be well to seek for it, in order to judge of that portion of the line. Fry and Jefferson's journal was burnt in the Shadwell house about fifty years ago, with all the materials of their map. Walker and Smith's survey is probably in our offices; there is a copy of it in the atlas before mentioned; but that survey was made on the spur of a particular occasion, and with a view to a particular object only. During the revolutionary war, we were informed that a treaty of peace was on the carpet in Europe, on the principle of uti possidetis; and we despatched those gentlemen immediately to ascertain the intersection of our Southern boundary with the Mississippi, and ordered Colonel Clarke to erect a hasty fort on the first bluff above the line, which was done as an act of possession. The intermediate line, between that and the termination of Fry and Jefferson's line, was provisionary only, and not made with any particular care. That, then, requires to be re-surveyed as far as the Cumberland mountain. But the eastern and middle surveys will only need, I suppose, to have their longitudes rectified by the astronomical surveyor.