478 SCIENCE OF AGRICULTURE. Part II. 



SuBSECT. 1. Of Measuring relatively to Agriculture. 



5054. TAe7/iea5Mnng o/*^flnrf, or other objects, comprises three distinct operations; viz. 

 taking the dimensions of any tract or piece of ground ; delineating or laying down the 

 same in a map or draught, and calculating the area or superficial contents. The dimen- 

 sions on a small scale are best taken by rods of wood, but in all ordinary and extensive 

 cases by a chain of iron, as being less likely to contract or expand by changes of temper- 

 ature, than cord lines or tapes. In measuring a simple figure, such as a square field, 

 nothing more is necessary than to take the length and breadth, which multiplied together 

 give the superficial area; but as few fields are square, or even right angled, it becomes 

 necessary to adopt some guiding line or form within the field, and, from that line or 

 form to measure to the different angles, so as to be able from the dimensions taken, either 

 to calculate the contents at once, or to lay down the form of the field on paper, according 

 to a certain scale, or proportion to its real size, and from that to take dimensions and cal- 

 culate the contents. The simplest and most accurate mode of ascertaining the contents 

 of all irregular figures is by throwing them into triangles ; and this also is the most accu- 

 rate mode of measuring and protracting a whole landed estate, however large. In short, 

 a triangle is the form universally adopted, whether in surveying a single field, or a whole 

 kingdom. To find the contents of a triangle every body knows that it is only necessary 

 to multiply half the perpendicular into the base. These two principles properly under- 

 stood, form the foundation of measuring, protracting, and estimating the contents of ter- 

 ritorial, and all other surfaces. In surveying hilly lands, an allowance is made both in 

 protracting them, and calculating their contents, well known to surveyors, and not 

 necessary to be entered into here. 



5055. In measuring solid bodies, the rule is to " find the area of one end, and multiply 

 that by the length." This rule is of universal application, whether to land as in excavat- 

 ing or removing protuberances ; to ricks of corn ; heaps of dung; timber; or water. The 

 area of one end, or of one surface, whether the end, side, top, or bottom, is found exactly 

 on the same principles as in ascertaining the superficial contents of land, and if the figure 

 diminishes in dimension in the course of its length, as the top of a rick, or tlie trunk of a 

 tree, the mean length or half is taken as a multiplier. 



3056. Measuring objects by the eye, though a mode that can never be depended on as 

 the foundation for any important calculation or transaction, yet should be constantly 

 practised by young men for the sake of gaining habits of attention, and acquiring ideas as 

 to number and quantity at first sight. The principle on which this sort of eye measure- 

 ment is acquired, is that of ascertaining the actual dimension of some near object, and 

 applying it as a measure to all the others seen beyond it. Thus, if a man is seen standing 

 by a post or a tree at a distance, taking the height of the man at five and a half, or six 

 feet ; apply the figure of the man to the tree, and find how many applications will reach 

 its top ; that number multiplied by the ordinary height of a man, will of course be a 

 near approximation to its height. Again, supposing this tree one in a row or avenue, 

 then to estimate the length of the avenue, measure the third or fourth tree by the man, and 

 measure by the same means the distance of that tree from the first, then state the question 

 thus : as the difference between the height of the first and fourth tree is to the horizontal 

 distance between them, so is the difference between the first and last tree of the avenue, 

 to the length of the avenue. In this way, the length and breadth of a field may be esti- 

 mated by observing the height of the hedge, at the nearest side, and the apparent height 

 at the farthest points. The breadth of ridges and their number, teams at work, or cattle 

 grazing, or accidental passengers, are all objects of known dimensions, which may be 

 made use of in this way of estimating the contents of lands. In regard to houses, the 

 doors, and windows, and size of bricks, stones, boards, tiles, &c. are obvious and certain 

 guides. 



3057. The recollection of surfaces and of country is a matter of considerable interest to 

 every one, but especially to the agriculturist. The most effectual mode of impressing 

 scenery on the memory is by the study and practice of sketching landscape. In addition 

 to this it will be useful to pay attention to the natural surface and productions, as, kind of 

 tree or crop, hills, valleys, flats, lakes, rills, &c. ; also, the distant scenery, as whether flat, 

 hilly, cultivated, waste, woody or watery ; what processes are going on ; what the style 

 of houses, dress, &c. Having attended to these details, the next and the most important 

 aid to the memory is, to recollect what portion of country already known to us it most 

 resembles. 



3058. In endeavoring to recollect the surface and objects composing an entire estate some 

 leading central object, as the house, should be fixed on, and the bearings of other objects 

 relative to it, ascertained in idea. Then either by going over the estate, or by a favorable 

 position on the house-top, or some other eminence, the outline of the fields, or other 

 scenery nearest the house, may be taken down, or remembered, and also the distant 

 scenery, or that exterior to the estate. In riding through a country which it is desired to 



