498 SCIENCE OF AGRICULTURE. Part II. 



should never be used, as from the moment it is finished its decay commences, and 

 pains or attention will be able to keep it in repair after it has stood two or three years. 



3071. Stone and imj" walls are also very common in many situations, where better and 

 more durable ones could be made at equal, perhaps less, expense. In many instances, 

 however, they are employed from necessity, where lime is either very dear, or not 

 obtainable at any price. 



3072. Mud walls, with a mixture of straw, were formerly frequent in many places, not only for surround- 

 ing small enclosures and stack-yards, but also for the walls of farm-houses and offices, and for subdividing 

 houses into different apartments. When either the outside walls, or the inside divisions of a house, 

 are to be made of these materials, the custom is, to take a small quantity of straw, and incorporate it 

 with a sufficient proportion of clay ; the straw in this case answers the same purpose as hair in lime- 

 plaster. When a sufficient number of small masses are made, the work is begun by laying a stratum at 

 the bottom of the intended wall ; this being done, and the different pieces firmly kneaded or worked 

 together with the hand, a flat deal board is applied on each side, which, being properly pressed and rubbed 

 against the building in a horizontal direction, not only serves to consolidate the work, but gives it a degree 

 of smoothness and uniformity ; successive strata are added, till the wall is raised to the intended height, 

 care being taken to taper it gradually upwards. Walls made in this way, if properly constructed, will 

 last for many years; and, if dashed or harled with lime at a proper season of the year, will have an 

 appearance no way inferior to such as are made with stone and lime ; along with this addition to their 

 appearance, the harling or dashing with lime, if properly done, will, by preventing the access of moisture, 

 render them much more durable. 



3073. Rammed earth, or en pise, walls are very common in France, both as fences and 

 walls for buildings. They have been described at great length in the Communications 

 to the Board of Agriculture, and in other works, and tried in various parts of this country 

 with tolerable success, though they are by no means suited either to our moist climate, or 

 degree of civilisation. In constructing them the earth is previously pounded, in order to 

 crumble any stones therein ; clay is added in a small quantity, about one eighth part. 

 It is all beaten and mixed up together by repeated blows with a mallet about ten inches 

 broad, ten or fifteen inches long, and two inches thick. The earth being thus pre- 

 pared, and slightly wetted, the foundation of the wall is dug. This is laid with stone ; 

 and, when it is about one foot high above the surface of the ground, planks are arranged 

 on each side, and the space between filled with the earth intended for the wall, which 

 is strongly beaten. This method is continued successively, till the wall is completed. 



3074. Stamped earth walls are the invention of Fran9ois Cointeraux. Earth prepared 

 j ^;^^ j \^ in the same manner as for rammed walls, is put into a mould or 

 H^ illl^^ ^^^ '^^ ^^y ^^^^' generally that of the proposed wall's thickness in 



4-^ width, one or two feet long, and about one foot high. {Jig. 491. a) 

 The mould is a strong oaken or iron box, and the earth being 

 placed in it, is compressed either by the action of a press acted on 

 by a lever or screw, or a stamping-engine similar to the pile-driver 

 or great forge-hammer. The stone, or solid body of earth (6), 

 thus acquired, is then used in the same way as common hewn stone, 

 and either bedded or merely jointed with lime-mortar ; it is then 

 washed or harled, both for effect and duration. Various machines 

 for forming bricks and stones for the ordinary purposes of building 

 fence walls, and sheds, and other buildings of one story high, may be 

 found in the eighth and ninth volumes of the Mechanic s Magazine. 



Chap. V. 

 Gates and Bridges appropriate to Agriculture. 



3075. The gate may be considered as a movable part of a fence, or as a frame of 

 timber, or iron, readily moved, and calculated to give a convenient inlet and outlet to 

 enclosures. Gates may be considered in regard to the principles of their construction 

 and fixing ; the materials of which they are made ; and their different kinds. 



3076. With respect to construction, the great object is to combine strength with light- 

 ness. The absolute strength of materials depends on their hardness and tenacity. A 

 gate, therefore, consisting of one solid plate of wood or iron, would seem to require most 

 force to break or tear it in pieces : but this would not be consistent with lightness and 

 economy, and in the use of such a gate it would be found to open and shut with more 

 difliculty than one less strong. The skeleton of a plate of wood or iron is, therefore, 

 resorted to by the employment of slips or bars, disposed and joined together on mechanical 

 principles. These principles, applied to carpentry, direct the use of what are called ties 

 and strutts, in the judicious composition of which, as far as construction is concerned, 

 consists the whole art of carpentry. A tie {Jig. 492. a) is a bar, or piece of timber, so 

 placed in a structure as to resist a drawing or twisting power ; a strutt (b) is one so placed 

 as to resist weight, or whatever has a tendency to press or crush. The horizontal bars of 



