114 



THE IKKIGATION AGE. 



found in the Appendix, to which the reader is referred. 



For ordinary purposes a knotted cord or tape-line 

 may be used. In measuring a simple figure, as a 

 square field, nothing is necessary but to measure the 

 length and the breadth, which, multiplied together, will 

 give the superficial area. Where fields are irregular 

 shaped, it is necessary to adopt some standard guiding 

 form, and from that measure 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 the scale adopted, 

 and from that ascertain its dimensions and calculate 

 its contents. 



The simplest and most accurate mode of ascertain- 

 ing the contents of all irregular figures is to throw 

 them into triangles, and this method is usually employed 

 whether a small piece of irregular shaped land is to be 

 measured or a vast extent of territory. To find the 

 contents of a triangle all that is necessary is to mul- 

 tiply half the perpendicular by the base. And this re- 

 gardless of the shape of the triangle. In measuring 

 land in this manner, and by a little calculation, every 

 foot of land can easily be represented on paper. 



TAKING THE LEVEL. 



After tho land is accurately measured, or measured 

 satisfactorily to its owner, taking the level of its sur- 

 face is the next thing in order, and in this there can 

 nipt.' be too much care taken, particularly where irri- 

 gation is practiced. Upon it depends the proper flow 

 of water in ditches, the flooding of land and adequate 

 drainage. 



To explain it will be necessary to be a little ab- 

 struse, but the idea will be readily grasped by think- 

 ing. The earth is a sphere, that is, "round," and all 

 places on its surface, whether a ten-acre tract or one 

 of ten thousand, are said to be "level" when they are 

 equally distant from the center of the earth, and "out 

 of level" when their distances from that center are not 

 equal. 



Now, because the earth is a sphere, or round, every 

 level line drawn upon its surface from one point to 

 another, must be a curve and part of the earth's circum- 

 ference, assuming it to be perfectly smooth, or at 

 least parallel with it. 



The common methods of leveling are sufficient for 

 irrigation on an ordinary tract of land, but for long 

 canals and ditches miles in extent, the leveling must 

 be in accordance with the curved level line to corre- 

 spond with the surface of the earth equi-distant from 

 its surface. The usual instrument for leveling is the 

 road or mason's level with telescope and compass, the 

 latter to get the bearings. For ditching purposes a 

 "plumb-bob" level, a two-legged contrivance open like 

 the letter A with a line fastened at the top and ter- 

 minating in a pear, or "top" shaped piece of lead. In 

 the exact center of the bar across the A is marked a 

 notch, and when the point of the "bob" is at that 

 center notch, the line is level. Illustrations of this 

 and other contrivances for leveling land will be found 

 elsewhere, and referred to in the synoptical index so 

 as to be easily found. 



To continue the level line a series of poles are 

 necessary. These are so placed that the one nearest 

 the eye conceals all the rest. To allow for inequalities 

 of surface, a notch is cut in the starting pole, or at' 

 the point where the level line begins, and that point 

 must be level with it all along the line. A small spirit 

 level held to each pole, and the eye will demonstrate 



the exact level line for all practical purposes. This 

 method is sufficient for small areas, to lay the level 

 of a ditch, or its laterals, but in large tracts, of course, 

 a surveyor should be called in. Every farmer with a 

 hundred acres to level can easily do the whole survey- 

 ing himself by following this apparently crude method, 

 and be as accurate in his leveling as a professional sur- 

 veyor. 



Where there are curved lines to be drawn on irreg- 

 ular surfaces, a hill or a knoll, for instance, being in 

 the way of a straight line, the mariner's compass may 

 he brought into use to ascertain bearings, and a series 

 of straight lines drawn which will make skeletons for 

 the curves. In fact, it is no trick at all to draw a 

 level line around a hill, or curve a ditch in the shape 

 of a letter S or Z, by this simple method. All these 

 measurements should be traced on the map, for even 

 if not used immediately they will prove useful when 

 necessary to ditch, or irrigate. 



The following table showing various grades per 

 mile will be useful as a basis of calculation in drawing 

 the level lines for ditches or general irrigation purposes : 



1 foot in 15 is 352 feet per mile 



1 foot in 20 is 2,64 feet per mile 



1 foot in 25 is 211 feet per mile 



1 foot in 30 is 176 feet per mile 



1 foot in 35 is 151 feet per mile 



1 foot in 40 is 132 feet per mile 



1 foot in 50 is 106 feet per mile 



1 foot in 100 is 53 feet per mile 



1 foot in 125 is 42 feet per mile 



Any desired grade or "flow" can be calculated by 

 remembering that there are 5,280 feet in a mile. By 

 dividing 5,280 feet by the number of feet in length of 

 the ditch, the grade or "fall" will be the result, esti- 

 mating one foot as the desired fall or flow of the water 

 in the ditch, and the desired fall or flow may be regu- 

 lated when drawing the level line by notching the 

 poles used in leveling. 



ELEMENTARY INFORMATION. 



To make this land leveling business clear to the 

 mind of the elementary reader, let it be supposed that 

 he desires to run a ditch from one point to another. He 

 has the letter A-shaped plumb-bob leveler, half a dozen 

 poles ten feet or so in length, and a carpenter's spirit 

 level. With these he is prepared to run practically 

 level lines all over a hundred-acre tract of land. 



At the starting point ascertain the "plumb" point, 

 that is, the spot over which hangs the lead bob exactly 

 in the middle of the cross-bar of the A, then plant 

 a pole, and at the height of the eye, say five feet, cut 

 a plainly visible notch, or make any kind of a mark 

 that can be seen from a distance. This is the standard 

 of the entire ditch. 



Next, take another pole, your A level, and the 

 spirit level, and walk along the proposed line of ditch 

 any convenient distance to a point. Four rods or so 

 are not too far, less if there are obstructions to level 

 around. Lay the A level over the selected point and 

 ascertain the exact level of point two, as it may be 

 called. Now place the spirit level against the pole 

 about the height of the eye, and look along its top just 

 as if "sighting" a gun. Slide it up and down, if nec- 

 essary, until you find the notch in the first pole, with 

 the "bubble" in the spirit level exactly in the center, 

 and make a notch or mark in pole number two where 

 the top of the spirit level touches it. 



A calculation is easily made, for the notch on pole 

 one is five feet from the surface of the ground, and by 

 measuring the height from the ground of the notch in 



