To convert links to feet.-Multiply by 66 and mark off the last two figures (i.e. divide by 100). = Example.-50 links 50 x 66 = 33.00 feet. To convert links to yards.-Multiply by 22 and mark off the last two figures. Example.-50 links = 50 × 22 = 11.00 yards. To convert feet to links.-Multiply by 100 and divide by 66. = = To convert yards to links.-Multiply by 100 and divide by 22. = CUSTOMARY AND STATUTE MEASURE Originally land measurement differed in various parts of England, being governed by custom: hence the term 'Customary Measure.' At the present time land measurement all over England is governed by Acts of Parliament: hence the term 'Statute Measure.' Three Acts are responsible for our present standards of measurement, viz. : 34 Henry VIII (1542) enacted that the acre should be 10 square chains. 5 George IV (1824) enacted that the yard should be called the Imperial Standard yard. It is the distance between two marks on a certain bar which is kept in the Standards Office at Westminster. (There is a replica let into the raised pavement on the north side of Trafalgar Square.) It also fixed our lineal and square measures as given in Chapter I of this book. 5 & 6 William IV. (1835) abolished all customary weights and measures. Occasions may occur, though very rarely, when it is necessary to reduce customary to statute measure. This may be accomplished as follows: Reduce the roods and perches to the decimal of an acre and multiply by the number of square feet or square yards in the customary acre. Reduce this quantity to acres, roods and perches by statute measure. Example.-Reduce 10 acres 2 roods 20 perches customary to statute measure, when the customary acre contains 4000 square yards. 10 acres 2 roods 20 perches = 10188 = 10.625 acres. 10.625 customary acres x 4000 (number of square yards in 1 customary acre) = 42500 (number of customary square yards). 425004840 (number of square yards in 1 statute acre) = 8.781 nearly. ... 8.781 = the area in statute acres. 4 3.124 ... The area in statute measure = (say) 8 acres 3 roods 5 perches. Systematic Surveying.—With a thorough understanding of the ordinary rules of mensuration, there is no doubt that the survey of a piece of country could be made and laid down to scale on paper by anyone of average intelligence, provided that he took sufficient and careful measurements. Each field would be measured separately, and the trouble would begin when the surveyor wished to join the fields together on paper so as to make a complete plan. This would be bad enough, but it would be nothing to the difficulty which would confront the draughtsman who had never seen the country in question: he would be utterly at a loss to place them in their relative positions from the surveyor's field notes. It is obvious then that a system is demanded, which will be understood by all surveyors. Equipment. First of all let us consider what equipment we shall require on setting out to make a complete chain survey of land. It should consist of a chain and arrows, already described, and the following: Ranging rods, poles, or pickets.-These are poles painted red, white, and black, of say 1 to 1 inches in diameter, and from 10 to 15 feet in length, shod with iron so as the more easily to be inserted in the ground. The longer poles should have a white flag attached to the top so that they may be seen at a distance. These poles or rods are used for marking the station points and ends of the chain lines. Cost from 30s. to 60s. per dozen. Pegs or false pickets, made of wood, about a foot long, pointed at one end and say 2 inches square at the other, for the purpose of marking stations. They should be driven into the ground to within 3 inches. Offset Pole. This is a rod of 10 links in length, each link being marked off in alternate bands of black or red and white: it is used for taking measurements from the chain line to inequalities in the boundaries: cost about 38. 6d. A tape may be used for this purpose also, but it is not advisable, as it is liable to become permanently stretched with use, and so inaccurate. It is a nuisance when the ground is wet, and is quickly spoilt in such conditions. A Field Book in which to enter measurements: a pencil and a piece of india-rubber. In addition to the above mentioned we might include a Cross-staff or an optical square, both of which will be described later, a bundle of laths or sticks called 'whites' for lining out the chain line if very long, a pair of field glasses, and three assistants. Cadastral and Geodetic Surveys.-It might be mentioned here that the scope of this book does not extend beyond what is known as Cadastral Surveys. A Cadastral Survey is a field-by-field survey, made with the object of delineating correctly the boundaries of each field and showing its area and nature. The scale of such a survey, therefore, must be large enough to show clearly all detail; the 25-inch (20) Ordnance Survey map may be taken as a good example of a cadastral map. In cadastral surveys the spheroidal shape of the earth may be neglected, and its surface may be taken as a plane. We may, accordingly, solve all problems in this connection by plane trigonometry, and the error thus introduced will be a negligible quantity. The sides of the triangles in such surveys are taken as straight lines when they do not exceed six miles, but in longer lengths than six miles the curvature of the earth must be taken into consideration. A Geodetic Survey, or trigonometrical survey, takes into consideration the shape of the earth, and spherical trigonometry must be used for the solution of the triangles laid down. That branch of surveying which deals with the survey of a country, or extensive areas of the earth, is termed Geodesy. Method of Chaining. The surveyor should take the chain when folded in his right hand, with both handles in his left hand, and throw it sharply from him, keeping hold of the two handles. If the chain has been properly done up, it will fly' clear, without any knots in it. Poles are placed in the ground at the extremities of each line to be measured. Two men are required to 'run' a chain line, one to pull, called the 'leader,' and one at the other end to 'drive,' or give direction, called the 'follower.' The follower holds the handle against the first pole, and directs the leader, who takes the ten arrows, in line with the pole at the end of the chain line. At the end of this chain, and of each successive chain, the leader puts in an arrow, and the follower collects them as they proceed, until all the ten arrows have been picked up or the end of the line has been reached, when the follower gives them back to the leader. The leader should carefully count them, on receiving them from the follower, to see that one has not been left behind. This is called a tally point. Tally points should always be booked in the field book, whether an offset has been taken from that point or not. To do up the chain after use, take hold of the round tablet at the centre, and double each pair of links backwards and forwards until the handles are reached; the chain when done up in this way should resemble a wheatsheaf: fasten with a leather strap. The arrows are best carried in a quiver, as they are dangerous things to have hanging loose, especially when getting over a fence. Inaccuracies in Chaining.-Some of the many causes of inaccuracies arise as follows: 1. Through not testing the chain before commencing a survey. In a large survey the chain should be tested daily. A steel tape is useful for this. 2. Through not pulling the chain tight when the arrow is put in by the leader. 3. Through the leader not putting in his arrow exactly perpendicular, and close to the handle of the chain. 4. Through the follower not keeping his arrow perpendicular when holding the handle of the chain against it. 5. Through not making allowance on sloping ground so as to reduce the measurement to the horizontal. 6. Through not taking sufficient care when traversing difficult ground, and going through fences. 7. Through not keeping in proper alignment. When a long line has to be chained it will help the chainmen to keep in a straight line if intermediate points between the stations are ranged in at regular distances. For this purpose a bundle of laths is useful. Whites, as they are called, may be cut for this purpose from underwood about 3 feet long. A piece of white paper inserted in a cleft at the top of the stick will enable it to be seen more easily. 8. Through a knot occurring in the chain, or a link becoming bent or kinked. 9. Through the follower losing an arrow. 10. Through reading the links at the end of a chain line, or booking them, wrongly. 11. Through variation of temperature from which the chain expands or contracts. In this country, however, a variation of 80° F. (which more than covers the ordinary range of the temperature in winter and summer) makes a difference of about half an inch in a chain's length, which is practically negligible. Chain Error. The correct length of a chain on the ground is from the outside of one handle to the outside of the other. chain should be held thus : The If both arrows are outside the handles the thickness of an arrow is added to the length of the chain. If one arrow is outside the handle and the other inside, then the thickness of a handle is lost. If the chain is incorrect in length to start with, its error should be noted in the field book at the beginning and end of every day's work, and the mean taken as the correction required. Correction of Chain Error.—When a line has been measured with an incorrect chain, the true length of the line may be found by proportion. The length of the correct chain is to the length of the chain used as the measured distance is to the true distance. Example.-Suppose a chain has stretched 3 links and the measured distance is twenty chains. Then 100 103:: 2000: true distance ... THE TRUE DISTANCE IS 20.60 CHAINS The Surveyor's Field Book.-A surveyor's field book is used to record the sketches and measurements which have been made on the ground. It is of pocket form (i.e. opens from the end) and is usually about 8 inches long and 4 inches wide. There are two methods of ruling the pages, one with two lines down the centre of the page lengthwise, forming a middle column, and one with one line. The double line, or single line, represents the chain line, and between them, or on it, are recorded all the measurements made on the ground which refer to the length of the chain. It is open to argument as to which is the better method, and it is probably only a matter of taste. With the double line all the chain measurements are kept to themselves, and there is little likelihood of their being mixed up with the offset measurements, which are placed alongside at right angles. With the single line there is this advantage, that more room is allowed for sketching in fences and detail at the side, and when a fence crosses the chain line, it can be drawn across the single line, which may not be done when two lines are used. A reference to Figs. 2 and 3 will make this clear. With reference to Figs. 2 and 3. be done as follows: The entry of the work should |