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fmall conduit at the lowermoft corner of each field, as is reprefented by the dotted lines L, L, L, L. Each of these fhould be carried quite thro' the bank from the ditch L, (Fig. 14th,) as reprefented by the dotted lines L, H, and should be built of folid mason-work, well rammed at the back with soft clay, to render it quite impervious to water. At L, (Fig. 14th,) there should be formed a close water-fluice that could be opened or fhut at pleasure; and, on the other end of the conduit, at H, there fhould be a wooden door with the hinges upon its upper-fide, fo as to make it open with its back towards the ftream; by which means, when the water of the river rifes above the level of the line LH, it will press upon the back of the door, fo as to fhut it, and prevent the water from flowing into the field at that time; and, when the river again falls to its ordinary level, the door will be easily forced up by the preffure of the water from within, if there

has

has been any accumulated there during the time of the inundation, and it will be allowed to fall easily into the river.

This kind of fluice is well known, and has been frequently defcribed; but, as it is difficult to get them made to close fo exactly as to admit of no water at all, I have directed to employ likewife the inner-fluice at L, which could be made to fhut more accurately, and could be closed upon extraordinary occafions; and the folding fluice would be of use to keep out a good deal of the water when the inundation happened in the nighttime, or fo fuddenly as to be pretty high before the farmer could have time to get the innerfluice ftopped. The inner-fluice alone would be entirely fufficient, unless where there happened to be fprings within the field; which being kept in general fhut, could be opened when occafion might require.

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§. XXXII.

Directions for floating thefe Fields at Pleasure..

But this is not the only use that might be made of these fluices. Water is only prejudicial to the farmer when it comes at improper feasons, or in an impetuous manner, or remains longer upon the ground than he might incline; but, if it is entirely under his command, he may often employ it with very great advantage. Many of the fields in Holland are covered all winter with water, and are, by this means, rendered extremely fertile. And, as all rivers during inundations are ftrongly impregnated with the finest ticles of vegetable mold, and rich manures washed away from fertile fields by the violent rains, it is not to be doubted, but that,

par

if

if the water, when in this ftate, was allowed to glide flowly in upon a field till it was covered with it to a confiderable depth, and there detained in a stagnant state till all these fine faeculae were depofited upon the field, and was then drawn gently off, it would afford a very rich and valuable dreffing, somewhat fimilar to that which annually fertilizes Egypt by the overflowing of the Nile. For this river, coming with great rapidity through the country of Ethopia, enters Egypt strongly impregnated with the best vegetable mold; and, gliding flowly over these level plains, being still farther retarded in its course by the north wind, which at that time continually blows upon this coaft, the earth is allowed gradually to fubfide, and forms that rich flime which covers the whole country when the Nile retires within its bed, and gives to it the amazing fertility for which Egypt has been famous fince the ear lieft ages of antiquity. Now, although it is

not

not to be expected, that an inundation which continues only for fuch a fhort time, and rifes to fuch an inconfiderable height above the furface of the earth, as any that we ever experience, could produce fuch great effects as this more perfect annual overflowing does with them; yet, by the contrivance I have mentioned, the farmer might reap the fame improvement in kind, although not in degree; and, having it in his power to repeat it as often as an inundation happened, if he should so incline, it is hard to tell what a degree of fertility this might produce in time.

To obtain all these advantages, when he wishes to lay any particular field under water, he needs only to put a gag into the folding fluice, fo as to prevent it from shutting close; and having, at the fame time, opened the inner-fluice, allow it to remain in that ftate till an inundation happens; at which time the water from the river will enter free

ly

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