proper to

and minutes, and alfo its length must be accurately measured to feet and parts, either by a measuring chain, or by a piece of log-line of 100 feet long, properly marked at the end of every 10 feet. From one end of the base observe, with any inftrument take bearings, the pofition or bearing in degrees and minutes of all the ftaves or objects within view, and write them down orderly; do the fame from the other end of the bafe, and let all the bearings be corrected by the variation of the compafs.

Then these measures and corrected bearings being plotted or laid down, will give the most confpicuous points on fhore, the intermediate spaces are to be filled up from the fketches of them made on the spot.

But if any fuch objects should spread on either hand, fo far from beyond the limits of the bafe, that at either end thereof, the other end and thofe objects or ftaves fhould appear nearly in the fame direction, or to make <s of, not exceeding 10°: or, if fome of the remarked objects can be feen only from one end of the base, then let the bearings of fuch objects be taken from a place whofe pofition has been determined from both ends of the measured bafe; or if there are several remarked objects which cannot be feen from either end of the bafe lines, let the bearings of fuch objects be taken from each of the two points whofe polition has been taken from both ends of the bafe; or, it may on fome occafions be proper to choose another place on which another base of a convenient length may be measured, and from the extremities of which the ends of the first bafe may be feen, and alfo as many as can be of the remaining objects which lay too obliquely for the first base, or which could not be seen from it; in fuch manner proceed until the bearings are taken of all the points judged neceflary for completing the furvey of the limits of the harbour.

If a bafe line of a fufficient length cannot be measured in one right line, it may be taken in two adjoining lines, as the two fides of a triangle, the included angle being accurately taken, and the bearing of either line.

When the outlines or limits of an harbour, bay, road, &c. are delineated by the preceding precepts, let a fmall veffel go out to fea to take drawings of the appearance of the land, and ts bearings, fail likewife into the harbour, and draw the appearance of its entrance; take particular notice if there are any falfe refemblances of the entrance by which fhips may be deceived and run into danger; or when any two objects being brought in a line, or in one, will lead into the harbour without danger; when it can be done, fearch for the beft anchoring places, and if poffible denote thofe places, by bringing two objects in one, if not the exact bearings of two or three other objects, fo that the places may be easily determined, the chart being correctly drawn, a compafs with the variation, and scale properly fitted to the plan, the ifles, rocks, fands, &c. marked in their proper places, with their foundings at low water, and the winds open to them, the beft tract with the found

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ings all the way to those anchoring places, the proper failing marks to avoid dangers; the winds, if any troublefome ones, which prevail, and at what feafons; the places where fresh water can be got, the name of the place, the country in, on what fea, the latitude and longitude, a sketch of the appearance the place makes at fea upon a known rhumb, and at an elimated diftance, and whatever elfe a judicious feaman fhall think proper to infert; then is the plan fit for all nautical purposes, and may be embellished with proper colours, if neceffa y.

Sea-drawings, taken according to the foregoing precepts, befides the real use they are of, cannot fail to recommend the young mariner who furveys and conftructs them, to the notice of his fuperiors.

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To reduce a Draft to a fmaller Scale.

TITH a black lead pencil draw the draft to be reduced all over with cross-lines, forming exact squares, draw the clean paper for the copy all over with the fame number of fquares, but their fides larger or smaller in proportion to the intended fize of the fcale, fuch as,, &c. length of the other, diftinguish by a stronger mark, with a figure every fifth or fixth row of fquares in both, fo that the feveral correfponding fquares may be readily perceived; then, in each of the fquares of the draft, draw, by the eye, a curve on the paper, fimilar to that in the fquare of your copying draft, till the whole is copied; make the black lines with India or other ink, and when drawn, the black-lead lines may be rubbed out with bread or India rubber.

I here give two Examples, as an elucidation of what has last been faid.

BG=N. 5°E.

BC=N. 25 W.

EXAMPLE I.

AB is the bafe line, equal to 4 Mile.

2

3

at A

with

4

Bear

AH S. W. 5
AF-S.E.

ings.

6

BD=N. 53 W.
Station at B, AD N.53°25'W.3
BE W.S.W. 4with Bearings. E S. W. by W.
BH S.W.by S.W.5

These inftruments give the points GC DE HF in order from each station; that is, BG and AG interfect, as also BC and AC, &c.

Obferve, the last letter must be the fame in both bearings, and it will be the best to follow the bearings one way all round the compafs from the first station; as alfo when arrived at the second station, begin with your firft object feen at firft ftation, and follow the letters round belonging to each object, by which the last letter in each bearing will fucceffively follow in order.

This is an example when on board fhip.

Kk 2

EXAMPLE II.

This harbour was furveyed by base lines taken on fhore, which, when it can be done, is far preferable.

The bafe line AG 812 fathoms, was taken, as by directions, on the most even spot on fhore; now, beginning from the point A : JGB=S. S. W.

AB W. by S. S.
AC W. by N. Bearings GC W. by S. i S
AD W.N.W.IN. (from Sta-GD=W.IN.
AE N.N.W.W. tion A. GE=W.N.W.N.
AF N. by W.W.
GF N.W.by N.IN.
AGEN. N. E.

812 fath.

Bearings from .
Station G.

After having made these obfervations, it will be neceflary to proceed to the northern part of the coaft. In all cafes where a coaft is furveyed in several parts, it is moft advisable to measure a new fundamental base for each part, when it can be conveniently done. A line measured from the ftation F, towards K, is well adapted to our purpose. Let FK, therefore, be the second bafe line; its length, by admeasurement, is found to be 778 fathoms; and its bearing, by compass, N. F. E. Take bearings from each end of this bafe as before.

Bear

FlandFH N.W.byN.IN. | ings
FL=N. E.

FK N.E.E.778 fath.

from

(KF=S.W.W.
KH N.W.IN.
KI=W.IS.

Sta- KLN.by W.
JtionF LKN N.÷E.4W.

Bearings

from Sta

tion K.

It is plain, that the connection between the two parts of this furvey is preferved by the fecond fundamental base being drawn from the point F, whofe fituation was before determined by obfervations from the firft bafe line. If this particular pofition of the firft bafe line had not been convenient, and it had been taken at a distance from every point determined in fituation from the first base line, the connection would have required an observation of the bearing of one of the faid points from each end of the fecond bafe. Thus, fuppofe the line IK to be the second base line, inftead of FK, the pofition of IK, with refpect to the given point F, may be known by taking the bearing of F from I and K. The end of the fhoal, marked M, lies with D, bearing N. and E. N. by E. E.

All the obfervations which are required to be made on shore being completed, through the interfections of the bearings draw the configuration of the coaft, as before directed, and finish the drawing by the inftructions there given; which, if well attended to, no difficulty can well occur.

To find the Height and Diftances of Objects at Sea. THEN the object is perpendicular, and the diftance to it can be measured, find the angle of altitude with a quadrant, and meature the diftance to it as exact as poflible, and then you have

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the