e20 PRACTICE OF AGRICULTURE. Part III. 



' 3820. Where there is deep cutting on one side (c), or both (rf, e), a bench or berm (d, e) is provided to 

 retain and prevent the loose earth that may moulder down from the upper bank from falling into the canal 

 The banks are usually made one foot higher than the water is intended to stand in them. 



3821. In level cutting {fig. 575. a, b), the height of the canal should be so contrived, that in any cross 

 section the sura of the areas of the made banks (, b) should just equal that of the area of the section of 

 excavation (i). 



3822. In side-lying ground (fig. 575. c, and fig. 576./), the same object may be attained with a little extra 

 calculation j and in all other cases {g, h), the engineer will show the perfection of his skill in so conducting 



576 .. - . 



the line, that every embankment shall have deep cutting at both, or at least at one of its ends, to furnish 

 the extra stuft'with least expense in moving it; in like manner, every deep cutting (d, e) should have 

 embankments at one or both of its ends, to receive the extra stufK 



3823. Before cutting out the lock-spit, or small trench between the several slope holes, 

 as a guide to the men who are to dig, the engineer ought to cause holes to be dug in the 

 line of the canal, near every second or third level peg, or oftener, if the soil be variable, 

 in order to prove the soil to a greater depth, by two or three feet, than the cutting of the 

 canal is to extend ; and each of these the engineer ought carefully to inspect, in order 

 to determine what puddling or lining will be necessary ; and what will be the diffi- 

 culties of digging, owing to the hardness of the stuff, or to water that must be pumped 

 out, &c. ; all which circumstances, as well as the extra distance that any part of the stuff 

 may require to be moved, must be well considered before the work can be let to the 

 contractors. 



3824. The puddling or lining of the canal, to make it hold water, is a matter of the 

 greatest importance, and we shall consider five cases that are likely to occur or present 

 themselves in the search into the soil that is to be dug, by sinking holes as above 

 mentioned. The first case we suppose to be that in which the whole is clay, loam, or 

 other water-tight stuff; all soils that will hold water, and not let it soak or percolate 

 freely through them, are called water-tight. Our second case is that in which the 

 whole cutting will be in sand, gravel, loose or open rock, or any other matters that will 

 let water easily through them, and such are called porous soils or stuffs. The third 

 case, we suppose to have a thin stratum of water-tight stuff on the surface, and to have 

 porous stuff for a. considerable depth below. The fourth case may have porous stuff near 

 the surface, and water-tight stuff at the bottom of the canal. The fifth case is that 

 where water-tigh^ stuff appears on the surface ; and below this a stratum of porous stuff, 

 but having again water-tight stuff at no great distance below the intended bottom of the 

 canal. The new-raised banks are always to be considered as porous stuff, as, indeed, 

 they will always prove at first, and in a great portion of soils they would ever remain so, 

 unless either puddling or lining were applied ; all ground that has been dug or disturbed, 

 must also be considered as porous. It should also be remarked, that any kind of soil 

 which is perforated much by worms or other inset^s, should, in canal-digging, be consi- 

 dered as porous stuff. 



3825. Puddle is not, as some have attempted to describe it, a kind of thin earth mortar, spread on places 

 intended to be secured, and suffered to be quite dry before another coat of it is applied ; but it is a mass of 

 earth reduced to a semifluid state by working and chopping it about with a spade, while water, just in the 

 proper quantity, is applied until the mass is rendered homogeneous, and so much condensed that water 

 afterwards cannot pass through it, or but very slowly. 



3826. The best puddling stvff'is rather a lightish loam, with a mixture of course sand or fine gravel in 

 it ; very strong clay is unfit for it, on account of the great quantity of water which it will hold, and its 

 disposition to shrink and crack as this escapes ; vegetable mould, or top soil, is very improper, on account 

 of the roots and other matters liable to decay, and leave cavities in it; but more on account of the tempt- 

 ation that these aftbrd to worms and moles to work into it, in search of their food. Where puddlin^' stuff 

 is not to be met with, containing a due mixture of sharp sand, or rough small gravel stones, it is not 

 unusual to procure such to mix with the loam, to prevent moles and rats from working in it; but no stones 

 larger than about the size of musket bullets ought to be admitted. 



3827. That the principal operation of puddling consists in consolidating the mass, is evident from the 

 great condensation that takes place ; it is not an uncommon case, where a ditch is dug, apparently in firm 

 soil, that though great quantities of water are added during the operation, yet the soil which has been dug 

 out will not, when properly worked as puddle, fill up more than two thirds of the ditch. It should seem, 

 also, that puddle is rendered by that operation capable of holding a certain proportion of water with great 

 obstinacy, and that it is more fit to hold than transmit water. It is so far from true, that puddle ought 

 to be suffered to get quite dry, that it entirely spoils when by exposure to the air it is too rnuch dried ; 

 and many canals which have remained unfilled with water during a summer, after their puddling or lining 

 has been done, have thereby become very leaky, owing to the cracks in the puddle-ditches or lining. One 

 of the first Carfes of an engineer, when beginning to cut a canal, is to discover whether good puddling stuff 

 is plentiful; andj if it is not, it must be diligently sought for, and carefully wheeled out or reserved 

 wherever any is found in the digging; or, perhaps, it must be procured at considerable distances froni the 

 line, and brought to it in carts. It has happened in some stone brash or loose rocky soils, that all pudxlling 

 stuff for several miles of the line required to be brought to it; but even this expense, serious as it may be, 

 ought not to induce the imitating of those, who have left miles of such hanks without puddling, and have 

 made a winter canal, but one which no stream of water that is to be procured can keep full in the summer 

 months. It is usual in canal acts to insert a clause, for the security of the landowners, to require the 

 company to cause all the banks that need it to be secured by puddling, to prevent damage to the land 

 below by leakage ; and it would have been well for all parties, in many instances, if this clause had been 

 enforced. 



