neither too high, nor too low, to permit the staff being read when held upon the Contour. Send the staff to the visible extremity of the Contour, and read the level; move the staff in the direction of the Contour, and every point where the same reading is obtained, with the same position of the instrument, will be a point in it. When as many points have been fixed as are necessary. to trace the part of the Contour visible from the instrument, take the angle between the last point fixed and some point given in the trace, unless the situation of the last point is known by being close to some object given in the trace; lay down the direction of the line from the instrument to the last picket; chain the line, fixing the points of Contour by offsets, as they are successively passed; and add the work to the trace as it proceeds.

Thus if the true instrument be placed at f, (fig. 6) its position may be fixed by measuring its distance from each of the pickets marked 260 and 270; the staff being read, or adjusted when held at 270, may be moved to g, h, i, and 270 (as a check) in the boundary line B C, the exact place for the picket at g, h, or ¿, being determined by moving the staff up or down the slope until the: reading on the staff is the same as at 270 in the line A B.

With the same position of the instrument, if the staff be about 12 feet in length, the points l, m, n, in the Contour 265, and the points o, p, q, in the Contour 260, might be established, the staff being read, or adjusted at the picket 265, before it is sent along the former Contour, and at the picket 260, before it is moved along the latter; by measuring the line f, k, these points may be determined by offsets, and the Contours drawn upon the trace. From the same point also, all the pickets required to describe the Contours having the levels 260 and 265, and lying wholly within the triangle, may be fixed, since the Telescope of the instrument would be higher than the summit they surround; and by measuring the line f, t, these Contours could be added to the trace.

It is not necessary to trace every Contour instrumentally: if the Contour 275 has been thus traced, the two between 275 and 260 can be added very correctly by the eye while the Contour 260 is being traced, by judging each time a picket of the latter is fixed upon the trace, how the interval should be divided to accord with the appearance of the ground.

Neither is it always necessary to fix the position of the instrument, for the pickets may often be surveyed without measuring from it; but wherever angles are used to set-off the measured lines it is necessary, and may be considered the general rule.

A single position of the instrument will seldom trace a Contour,-fences, &c., as well as the form of the ground, preventing it. If the instrument were placed at r, to trace the level 255, the last picket would probably be at S, the angle between the corner of the house, H, and the picket, s, might be observed, protracted on the trace, the line measured, the several pickets as far as s added to the plan, the instrument removed to s, and the Contour completed.

But the instrument might, in the case represented, be placed near s, its position being fixed, if necessary, by measurement from any of the points recognized on the trace, as the angles of the adjacent fence; from this point the whole Contour could be traced, neither buildings, fences, nor other objects intervening.

If the triangle be very large, and the Contours inconveniently long, it may easily be divided, and a dividing line should, if possible, be chosen running along one of the ridges of the ground; for the ridges afford the best sites for the instrument in tracing; and the ridges and valleys are convenient situations for check lines, because those measured to survey the pickets having to change their direction in crossing them, can then be closed upon points already fixed. The line TV would be a good dividing line in the figure, running along the ridge on which the point s is marked, and fixing two points in each of the Contours of the summit within the triangle.

- If it be required to Contour a single feature of ground, not as part of a large survey, but for some particular object, run lines from the summit along the several ridges of the ground, fix upon these lines the points where the Contours will intersect them, and trace, as above, the Contours between them: if the number of check lines be too few, run them in the valleys also.

CHAPTER XXV.

ON THE RECESS, OR OFFICE DUTIES OF A REVENUE SURVEY, PREPARATION AND COMPLETION OF MAPS AND AREAS, REDUCTION OF MAPS, &C.

HAVING described in the previous Chapters the several operations in the field, and the extent to which the results are there perfected, it is now necessary to particularize the equally important and laborious duties connected with the office, as pursued in the recess months, which, forming a considerable portion of the work to be accomplished within the year, requires no little tact and method to ensure its completion ere a fresh season demands the attention of the Surveyor.

The recess in Bengal, already alluded to at page 310, comprises the months from 1st of June to the middle of November, the rains generally driving the survey parties into the station or cantonments about the former dates, whilst the state of the country prevents an earlier assumption of field duties than the latter named period, or even the 1st of December. In the North-Western Provinces, little can be done in the field in May, whilst the recess terminates as early as the 15th October, by which time the country and climate is very favorable for active operations. During these months, the Surveyors and their establishments are employed in putting the field-work into a complete and tangible form, and preparing the several records and documents called for by Government, it being both expected and exacted, that the whole of the maps and calculations of one season be duly lodged and furnished to the

respective authorities, prior to the commencement of another season's work.

The office duties of a Revenue Survey may be divided into the following heads, and in this order we propose alluding to them:

Computing.

11. Comparing and Examining.

12. Filling in Village Plan Registers.

13. Formation of Pergunnah Volumes, with Alphabetical Lists, &c. &c.

14. Division of labor.

In Chapter X., page 302, we have detailed the mode of calculation pursued, by the system of co-ordinates obtained from the sine and co-sine of the angle, which the side makes with the meridian of every line surveyed, and shown that there are certain proof columns of the Traverse Table, to which every circuit must be rigorously subjected at the time of survey, so much of the Traverse Table (columns 1 to 9, page 301,) being complete, the field-work is deemed satisfactory, and the remainder may with safety be left to any subsequent period. The plotting columns 10 and 11, or differences of latitude and departure, are then worked down for the purpose of laying down the survey on paper and it has been shown, that where the N., S., E. and W. columns are proved, the protraction of the survey is certain and beyond all doubt, by means of columns 10 and 11 which likewise prove themselves, by coming out 0-0 or by the last differences of