meridian, viz. 15.39, from c to C, and draw B C, so will B C represent the second line of the survey. Again move the moveable scale along the stationary one to the third north and south distance from the place of beginning, viz. 24.56, from a to d, and lay off the corresponding distance from the assumed meridian, viz. 28. 16, and draw CD, which will be the third line of the survey. Proceed in the same manner till the whole be laid down, and ABCDEFG will be the required plot.

This method of plotting is by far the most perfect, and the least liable to error of any that has been contrived. It may appear to some to require more labour than the common method, on account of the computations required to be made for the preparatory table. These computations are however made with so much ease and expedition, by the help of the table in the appendix, that this objection would vanish, even if the computation were of no other use but merely for plotting; but it must be observed that these computations are of much further use in determining the area or quantity of land contained in the survey, which cannot be ascertained with equal accuracy in any other way. When this is considered, it will be found that this method is not only preferable on account of its superior accuracy, but is attended with less labour on the whole than the common method.

If a pair of scales, such as are above recommended, be not at hand, the work may be laid down from a single scale, by first marking off the N. and S. distance on the line N. S. and afterwards laying off the corresponding east distances at right angles thereto.

To plot the field notes, p. 318. 1. Lay down all the station lines, viz. 7° W. 21 chains, N. 55.15, E. 18. 20, &c. contained in the middle column of the field book, as before directed, without paying any regard to the offsets, until all the station lines,

Y

represented in fig. 3, pl. 18, by dotted lines, be laid down; then lay off the respective offsets at right angles from the station line, at the respective distances at which they were taken, as is done at fig. 3, a bare inspection of which will make the work perfectly plain.

To plot the field notes, p. 298. 1. Lay down the

whole of the outside boundaries, the station lines first, the offsets afterwards, as directed in the preceding articles; and then lay down the internal divisions or boundaries of the respective fields, in the same manner as is done in fig. 4.*

OBSERVATIONS ON PLOTTING, BY MR. MILNE.

The protractor, whether a whole or a semicircle, ought not to be less in diameter than seven or eight inches, to insure the necessary degree of accuracy in plotting the angles of a survey. The degrees on the limb are numbered various ways, but most commonly from 10° 20°, &c. to 360°. It would be right to repeat the numbers the contrary way, when the breadth of the limb will admit of it. Others are numbered 10° 20°, &c. to 180°, and contrary, Surveyors will suit themselves with that kind best adapted to their mode of taking angles in the field; so that in which ever way the limb of the instrument

* Mr. Gale's method of surveying and plotting is not entirely new: the first publication of them appears in a pamphlet printed in Dublin, 1760, entitled, A Method to determine the Areas of Right-lined Figures universally, very useful for ascertaining the Contents of any Survey. By the late THOMAS BURGH, Esq. Engineer and Surveyor-General of HIS MAJESTY's Fortifications and Buildings in IRELAND.

Mr. Benjamin Noble, in his Essay on Surveying, 8vo. Dublin, 1767, treats of this method under some improvement.

Mr. A. Burne, in his Surveying, 8vo. 1775, has avowed and adopted Mr. Burgh's method and tables.

Mr. Robert Gibson, in his Surveying, 8vo. Dublin, 5th edit. 1795, describes Mr. Burgh's method and tables, without any reference to him as the inventor. EDIT.

they survey be the same.

with is graduated, the protractor had best

It is true, a surveyor of much practice will read off an angle mentally very readily, in which ever way the instrument happens to be graduated.

For instance, I have in the field taken the angles made with the magnetic meridian, in which case I count no angle above 89° 59′; if the angle comes to 90° 0', I call it due E. or due W. if it is 89° 59′, I write to it N. E. or S. E. or else N. W. or S. W. as it happens to turn out.

Now 89° 59′ N. E. upon a protractor numbered to 360° 0', and placing 360 to the north, reads the same; but 89° 59′ S. E. reads 90° 1′, and 89° 59′ S. W. reads 269° 59′; and lastly, 89° 59′ N. W. reads 270° 1'.

Again, if the angle or bearing is due south, it reads on this protractor 180°; if 0° 1' S. E. it reads 179° 59'; and if o° 1' S. W. it is 180° 1'; and so of any other intermediate angle or bearing.

The great inducement to surveyors for taking the angles by the bearings the lines make with the magnetic meridian, is the having the needle as a check in the course of the survey; and when the circuit comes to be plotted, having it in his power to point off all the angles, or bearings of the circuit, at one planting of the protractor.

This mode of surveying, or taking angles, is also more expeditious, and more accurate than any other, provided the index of the instrument is furnished with a clamp for making it fast to the limb, while it is carrying from one station to another.

The protractor for plotting this way of surveying had best be graduated 10, 20, &c. to 180, on the right hand, and the same repeated on the left, and again repeated contrary to the former; but as protractors for general use are graduated 10, 20, &c. to 360, I shall here describe a very useful and convenient one of this latter kind, and then proceed to

represented in fig. 3, pl. 18, by dotted lines, be laid down; then lay off the respective offsets at right angles from the station line, at the respective distances at which they were taken, as is done at fig. 3, a bare inspection of which will make the work perfectly plain.

To plot the field notes, p. 298. 1. Lay down the whole of the outside boundaries, the station lines first, the offsets afterwards, as directed in the preceding articles; and then lay down the internal divisions or boundaries of the respective fields, in the same manner as is done in fig. 4.'

OBSERVATIONS ON PLOTTING, BY MR. MILNE.

The protractor, whether a whole or a semicircle, ought not to be less in diameter than seven or eight inches, to insure the necessary degree of accuracy in plotting the angles of a survey. The degrees on the limb are numbered various ways, but most commonly from 10° 20°, &c. to 360°. It would be right to repeat the numbers the contrary way, when the breadth of the limb will admit of it. Others are numbered 10° 20°, &c. to 180°, and contrary. Surveyors will suit themselves with that kind best adapted to their mode of taking angles in the field; so that in which ever way the limb of the instrument

Mr. Gale's method of surveying and plotting is not entirely new: the first publication of them appears in a pamphlet printed in Dublin, 1760, entitled, A Method to determine the Areas of Right-lined Figures universally, very useful for ascertaining the Contents of any Survey. By the late THOMAS BURGH, ESQ. Engineer and Surveyor-General of HIS MAJESTY'S Fortifications and Buildings in IRELAND.

Mr. Benjamin Noble, in his Essay on Surveying, 8vo. Dublin, 1767, treats of this method under some improvement.

Mr. A. Burne, in his Surveying, 8vo. 1775, has avowed and adopted Mr. Burgh's method and tables.

Mr. Robert Gibson, in his Surveying, 8vo. Dublin, 5th edit. 1795, describes Mr. Burgh's method and tables, without any reference to him as the inventor. EDIT.

they survey be the same.

with is graduated, the protractor had best

It is true, a surveyor of much practice will read off an angle mentally very readily, in which ever way the instrument happens to be graduated.

For instance, I have in the field taken the angles made with the magnetic meridian, in which case I count no angle above 89° 59′; if the angle comes to 90° o', I call it due E. or due W. if it is 89° 59', I write to it N. E. or S. E. or else N. W. or S. W. as it happens to turn out.

Now 89° 59′ N. E. upon a protractor numbered to 360° 0', and placing 360 to the north, reads the same; but 89° 59′ S. E. reads 90° 1', and 89° 59′ S. W. reads 269° 59′; and lastly, 89° 59′ N. W. reads 270° 1'.

Again, if the angle or bearing is due south, it reads on this protractor 180°; if 0° 1' S. E. it reads 179° 59'; and if 0° 1' S. W. it is 180° 1′; and so of any other intermediate angle or bearing.

The great inducement to surveyors for taking the angles by the bearings the lines make with the magnetic meridian, is the having the needle as a check in the course of the survey; and when the circuit comes to be plotted, having it in his power to point off all the angles, or bearings of the circuit, at one planting of the protractor.

This mode of surveying, or taking angles, is also more expeditious, and more accurate than any other, provided the index of the instrument is furnished with a clamp for making it fast to the limb, while it is carrying from one station to another.

The protractor for plotting this way of surveying had best be graduated 10, 20, &c. to 180, on the right hand, and the same repeated on the left, and again repeated contrary to the former; but as protractors for general use are graduated 10, 20, &c. to 360, I shall here describe a very useful and convenient one of this latter kind, and then proceed to