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and these are again subdivided, by the scale of the nonius, to every minute of a degree.

This limb is numbered from the right-hand towards the left, with 10, 20, 30, 40, &c. to 360 degrees.

4. The whole instrument fits on the conical ferril of a strong, brassheaded staff, with three substantial wooden legs, by which it can be firmly fixed upon the ground.

The top or head of the staff, consists of two brass plates, parallel to each other; and four screws pass through the upper plate, and rest upon the lower plate. By the action of these screws, the situation of the upper plate may be varied, so as to set the horizontal limb truly level, or in a plane parallel to the horizon.

NOTE 1.

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The compass is fixed on the upper plate of the horizontal limb; and the ring of the compass is divided into 360 degrees, which are numbered in a direction contrary to those on the horizontal limb. The bottom of the compass-box is divided into four parts or quadrants, each of which is subdivided to every 10 degrees; and numbered from the meridian, or north and south points, each way, to the east and west points. In the middle of the box is a steel pin, finely pointed, on which is placed the magnetic needle. The box also contains a small spiritlevel, fixed at right-angles to that which is attached to the telescope. By the assistance of these two levels, and the four screws before mentioned, the instrument can be placed in a truly horizontal position. (See the Description of the Compass, Part II.)

2. The method of using the theodolite may soon be acquired by a little practice in the field; but it will be obtained still more easily if the Learner be assisted by the instructions of a Practical Operator.

3. When trigonometrical calculations are to be made from the angles, they should, if possible, be taken to a minute; but an instrument that will take an angle to five minutes will answer very well for a Practical Surveyor; as angles cannot be laid down nearer, either by the line of chords or the protractor.

4. In order to lay down an angle by the protractor, draw a line at pleasure, for one side of the angle; apply the diameter of the instrument to this line, and its centre to the point where the angle is to be made; mark the point under the given degree, and through this point draw the other side of the angle.

5. To measure a given angle by the protractor, apply the diameter to one side, and the centre to the angular point; and the degree of the limb under which the other side passes, is the measure of the angle. (See Problems 19, 20, 21, 22, and 23, Part I.)

6. The following prices stand in Mr. Jones's Catalogue, for theodolites of different kinds; viz. a common theodolite, without rack-work, the horizontal limb six inches in diameter, eight guineas. Ditto, with rack-work movements, and which will take angles to two minutes of a degree, twelve guineas. Second best, 7 or 8-inch theodolites, which will take angles to a minute, sixteen guineas, and 22 £. 1s. Very best improved ditto, 33£. 128. Eight-inch ditto, 37£. 16s. Nine-inch ditto, 42£.

Directions for Planning Villages, Towns, and Cities.

All the main-lines must first be laid down; and the stations upon them marked off. The lines measured along the streets must then be drawn; and the stations upon them denoted. The bases of the buildings must next be laid down from the offsets, so as to form the streets"; and shaded as directed in Part V., and exhibited in Plate VII. The rough plan must then be transferred to a clean sheet, by some of the methods described in Part V., in order to make a finished plan.

The bases of all public buildings, such as churches, castles, prisons, session-houses, market-places, infirmaries, hospitals, mansion-houses, monuments, &c. &c. should be delineated upon the plan with the utmost correctness; and most Surveyors draw the bases of the columns which support the roofs of market-crosses, the galleries of churches, &c. &c. as exhibited in the plate to which we last referred.

The streets are usually left white; but some draftsmen prefer colouring the causeways, with a tint of blue, to distinguish them from the carriage-roads, which are generally washed with a yellowish brown.

The grass-plots, in gardens, public squares, &c. &c., whether they be rectangles, rhombuses, circles, ovals, or regular polygons, should be correctly delineated upon the plan; then shaded with Indian ink, and washed with green, in the same manner as pasture-grounds; and trees, water, pleasure-grounds, gardens, gravel-walks, &c. &c. must be shaded and coloured as directed in Part V.

The name of the village, town, or city, should be given in conspicuous characters, in some vacant part of the plan or map; and the names of all the streets, public squares, churches, colleges, halls, prisons, castles, court-houses, mansion-houses, market-places, lanes, alleys, courts, yards, &c. &c. must be entered in their respective situations, in the manner exhibited in Plate VII.

NOTE 1. If the dimensions be taken and laid down in feet, a scale of feet must be given; if in yards, a scale of yards must be given; if in chains and links, a scale of chains and links must be given; and if the town or city be very large, a scale of miles and furlongs may be given upon the plan, for the purpose of measuring distances; and as 220 yards make a furlong, the distance of one place from another may be easily obtained in miles and yards.

2. Any remarks or explanations that it may be thought necessary to give, may be entered in some vacant corner of the plan.

3. All plans, ornaments, &c. should first be drawn in pencil; and it will tend much to the improvement of the learner, if he form all his printing, German text, and large-hand letters by the pencil also, and then finish them with Indian ink.

4. In forming letters, ornaments, &c. with the pencil, the lines and strokes

should be made as fine as possible; as the ink frequently runs upon the lead, when the pencil has been used too freely; hence the necessity of applying Indian rubber after the outlines have been finely drawn with Indian ink, in order to remove the lead which is not covered by the ink, before we proceed to finish the letters, orna. ments, &c.

5. If the pupil does not succeed well in his first attempt with the pencil, the letters, ornaments, &c. must be effaced with Indian rubber; and he must repeat the process until he can form all the letters, devices, &c. correctly. Page 204.)

(See Note 6,

6. Brookman and Langdon's prepared lead pencils, marked F, for fine drawing, will be found to answer well in making letters, ornaments, &c.; as they are of a middling degree of hardness; consequently the marks made by them may be easily effaced. (See Note 4, Page 172.)

7. After practice has made the learner a proficient in penmanship, he will be able to print, text, and write more expeditiously, without the use of the pencil.

8. Here it may not be improper to caution the learner against a very common fault of young draftsmen; namely, that of making their lines and letters too strong, both with pencil and ink. The lines, dots, and letters belonging to wooden cuts should never be imitated by the learner, as they are mostly too strong and rough; but he should take for his pattern the specimens exhibited in the different copperplates given in this Work.

9. In Part the Second, ivory plotting-scales are recommended, as being the best; but it may be proper to observe that very good feather-edged plotting-scales are now made of box, by most mathematical instrument-makers, which will do very well for school-boys. A twelve-inch box scale may be had for about five shillings; but an ivory scale of the same length costs ten or twelve shillings, accordingly as it is finished.

10. What has been said on the subject of planning villages, towns, and cities, will be further illustrated by examining the plan of some large village, town, or city. The author recommends to those who desire to increase their information on this subject, a small plan of Leeds, neatly engraved; and sold by J. Heaton, Leeds, price 2s.; a large, elegant, coloured plan of Leeds, containing all the recent improvements; published by Longman and Co., London, price 21s. ; a small plan of London, neatly engraved, price 2s. 6d. ; also a new coloured plan of London, with its environs, including the surrounding villages. In this plan all the new roads, streets, buildings, bridges, squares, &c. &c. have been accurately inserted from original and actual surveys; together with the projected improvements not yet executed. Both these plans are published by Laurie and Whittle, London; the latter on a large sheet, price 6s. In this plan, the bases of houses are shaded with dots, in imitation of sand, as in the lower part of No. 2; but the bases of public buildings are shaded with lines, as in No. 7, Plate VII. The plan is surrounded by a border, which is divided into miles; and each mile is subdivided into eight equal parts or furlongs. Besides the above maps, it may be proper to observe that an excellent coloured plan of London and its vicinity, has lately been published by W. Darton, No. 58, Holborn Hill, London, on one large sheet, price 6s. 6d. A plan of Edinburgh might also be consulted with considerable advantage, by the Young Surveyor; as the New Town is laid out with remarkable regularity and elegance.

TO CLEAN PLANS OR MAPS.

It has been intimated to the young draftsman, in Note 6, Page 204, that every precaution should be taken to keep plans and maps clean, in executing them; but notwithstanding the greatest possible care be exercised, they will generally be somewhat soiled, (perhaps in consequence of misfortunes,) either by dust, ink, or colours; hence it is necessary to give the method of cleaning them after they are finished.

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NOTE. Not only the face but also the back of a plan should be cleaned, in order to make it look as well as possible; and give it the appearance of coming from the hands of a neat and elegant draftsman.

To clean Plans or Maps that are soiled with Dust, Indian Ink, or Colours.

Take a sharp penknife, with a roundish point, and scrape those parts gently which are besmeared with ink or colours, until you efface the blots; then use clean Indian rubber freely to those places that are soiled with dust; and lastly, rub the whole map well with white bread; taking care to pare the bread as it accumulates the dust.

NOTE 1. Indian rubber is made from the juice of a large and much branched tree, which grows in Guiana, Cayenne, and other parts of South America. The juice is obtained by making incisions through the bark of the tree, chiefly in wet weather. From the wounds thus formed, the juice, which is of a whitish colour, flows abundantly. It is usually brought to Europe in the form of pear-shaped bottles, which are made by spreading the juice over moulds of clay. These are exposed to a dense smoke, or to a fire, till they become so dry as not to stick to the fingers; and then by certain instruments of iron or wood, they are ornamented on the outside with various figures. This done, the clay, in the inside, is moistened with water, and then picked out by proper instruments.

2. When Indian rubber has become foul by frequent use, it may be cleaned by washing it in lukewarm water and soap.

To clean Plans or Maps that are blotted with Common Ink.

If the blots be light, they may be scraped out with a penknife, or effaced by rubbing them repeatedly with clean paper wet in water or saliva; but when they are deep, acid or salt of lemons must be used in the following manner: Dissolve a small portion of the acid in hot water, and with a clean hair-pencil, dipped in the solution, wash the blots until they are discharged.

NOTE 1.

Recent blots are easily obliterated; but when they are old, and very

deep, it will be found necessary to let the paper dry, and repeat the wash several times. Salt of lemons is sold in small boxes, by druggists.

2. When you have to write upon those places from which the blots have been removed, the paper will bear the ink better, if you rub a little pounce upon it, with clean paper; and then smooth it with your folder, or with the haft of your penknife. Sometimes the paper will bear the ink pretty well, after a blot has been removed, by merely smoothing it as above directed.

3. Pounce or gum sandarach is a resinous gum which exudes from the junipertree; and is of a pale yellowish colour. It is imported from the continent in small pieces or tears, about the size of peas; and when reduced to powder, and passed through a fine sieve, it is used for rubbing upon writing paper, in places where any blot or writing has been scraped out.

4. Sometimes a spurious kind of pounce is made by reducing resin (the juice of the Scotch fir) to a powder; but this should never be used, as it is too gummy. It may be known from genuine pounce by being of a darker yellow, and having a stronger odour.

5. Large blots of Indian ink, common ink, or colours, may be removed from maps or strong drawing-paper, by washing them repeatedly with a sponge and clear water; always taking care to squeeze and wash the sponge as it absorbs the ink or colours; repeating the process until the blots disappear.

6. Sponge is a kind of marine, animal production, formed by a species of worms, and found adhering to rocks, shells, &c. chiefly in the Mediterranean Sea. The best sponges are those which are white, light, and have the holes small, and near to each

other.

7. Sponge is much used by landscape painters, in washing their pieces with water, after they have finished shading them with neutral tint. This process removes the superabounding shade; discharges the clouds; produces a remarkable softness; and prepares the pieces for taking the colours with ease and freedom.

SECTION II.

DIRECTIONS FOR MEASURING AND PLANNING BUILDING GROUND, AND DIVIDING IT INTO CONVENIENT LOTS FOR SALE.

Directions for Measuring Building Ground.

LAND lying in the vicinity of large towns, is frequently sold by the square yard, for building-ground; and as it always bears a high price when the situation is eligible, it is of the greatest importance, both to the buyer and seller, to ascertain its content with the utmost accuracy.

In order to accomplish this desirable object, the dimensions should be very correctly taken, with a measuring-tape, divided into yards, tenths, and hundredths; or with a tape divided into feet and tenths; or feet and inches.

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