786 



THE IRKIGATION AGE. 



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 contest 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 con- 

 tents. 



The simplest and most accurate mode of ascertaining the 

 contents of all irregular shaped 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 multiply half the perpendicular by the 

 base. And this regardless 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 the land is accurately measured, or measured satis- 

 factorily to its owner, taking the level of its surface is the 

 next thing in order, and in this there can not be too much 

 care taken, particularly where the irrigation 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 abstruse, 

 but the idea will be readily grasped by thinking. The 

 earth is a sphere, that is, "round," and all places on its sur- 

 face, 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 circumfenrence, assuming 

 it to be perfectly smooth, or at least parallel with it. 



The common methods of leveling are sufficient for irri- 

 gation 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 correspond 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 terminating 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 that center notch, the line is level. Illustra- 

 tions 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 demon- 

 strate 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 sur- 

 veyor should be called in. Every farmer with a hundred acres 

 to level can easily do the whole surveying himself by follow- 

 ing this apparently crude method, and be as 1 accurate in his 

 leveling as a professional surveyor. 



Where there are curved lines to be drawn on irregular 

 surfaces, a hill or a knoll, for instance, being in the way 

 of a straight line, the mariner's compass may be 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 264 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 re- 

 membering 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 

 gjracle or "fall" will be the result, estimating one foot as the 

 desired fall or flow of the water in the ditch, and the desired 

 fall or flow may be regulated 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 

 ditsance 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 necessary, 

 until you find the notch in the first pole, with the "bubble" in 

 (he 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 pole number two, 

 any variation will mean that another level point must be 

 selected, or that there must be some grading or digging. 



The second level point having been established, proceed 

 with the third pole in the same manner, comparing it with 

 the second pole, carefully noting the figures on paper, and so 

 continue until the work is completed. Laterals may be run 

 in the same manner, and the entire parcel of land gone over, 

 the results in figures showing the slope or lay of the land 

 for every purpose. This leveling, if carefully and completely 

 done, will show numerous grades, or slopes' in the same parcel 

 or tract of land, and the knowledge of this is extremely valu- 

 able; in fact, necessary for irrigation purposes, whether ditch- 

 ing or flooding. It is often a very intricate matter to irri- 

 gate every portion of a given field uniformly, and failure to 

 do so always results in lack of uniformity in any crop sought 

 to be grown upon it, there being too much water on some 

 parts and not enough on others. It will be understood that 

 the waste of -water and the loss in crop must exceed by far 

 the expense of leveling the land in every direction. The 

 chapter on irrigation will give details of flowing water on 

 irregular surfaces, and reference to the synoptical index will 

 point out comprehensive illustration's. 



Before concluding this portion of the chapter on "Lay- 

 ing Out of Land," it is proper to add by way of information, 

 that on July 28, 1866, the Congress of the United States legal- 

 ized what is known as the "metric" or French system of 

 measurements, and provided that "It shall be recognized in 

 the construction of contracts. .*..*..*..*. .as establishing 

 in terms of the weights and measures now in use in the 

 United States, the equivalents of the weights and measures 

 in common use." 



That portion of the "French" system relating to land 

 measurement is given here, in case any farmer should fancy 

 it in preference to the "English" system, which has always 

 been used : 



Measures of Length. 



Metric Denominations and Equivalents in Denominations 



Values. in Use. 



Myriametre ... .10,000 metres 6.2137 miles 



Kilometre 1,000 metres 0.62137 mile, or 3,280 ft. 10 in. 



Hectometre .... 100 metres 328 feet 1 inch 



Dekametre 10 metres 393.7 inches 



Metre 1 metre 39.37 inches 



Decimetre ..1-10 of a metre 3.937 inches 



Centimetre. .1-100 of a metre 0.3937 inches 



Millimetre. .1-1000 of a metre 0.0394 inch 



