500 SCIENCE OF AGRICULTURE. Part II 



wind. The two points in the heel of the gate, to which the thimbles are fastened, may be considered A 

 firm or fixed points. From these points, viz. 1 and 2, {fig. 494.) two braces proceed to 4 and 3 in the middle d 

 the bottom and top bars, and being there secured, these become fixed points, and from these two points, viz, 

 4 and 3, two braces proceed to 5 and 6, fixing those jwints. The gate is thus doubly braced, viz. from the 

 top of the heel to the top of the head, by means of the braces 1, 4, and 4, 5 ; and from the bottom of tha 

 heel to the bottom of the head, by means of the braces, 2, 3, and 3, 6. On each side of the gate are tw4 

 braces, and those parallel to each other. The brace proceeding from the bottom of the heel of the gate, 

 and that which is parallel to it, as also the bottom bar, are all strained in the way of compression ; and 

 the brace proceeding from the top of the heel, and the other brace which is parallel to it, and also the top 

 bar, are all strained in the way of extension. The strains in this gate being none of them transverse, but 

 all longitudinal, it would support a vast weight at its head, without having its form altered. All the 

 braces serve the double purpose of keeping the gate in its due form, and of shortening the bearings of the 

 bars, and strengthening them. Few gates have less timber in their braces, and^ perhaps, in no other way 

 can a gate be so firmly braced with so small a quantity of timber. At 3, 4, 7, and 8, two braces and a bar 

 of the gate are firmly screwed together, by meafis ftTif On pins and screw-nuts. At the other points, where 

 only one brace crosses a bar, common gate-nails are used. To resist the pressure of heavy cattle, a bar, or 

 board, about six inches broad and one inch and a quarter thick, should be laid with its broad side upon the 

 top bar (see section at C), and fixed thereto by means of the ends of the braces in the middle, and by the 

 head and heel of the gate at the two ends of it. This board wilF, in tJ)ispositipn, resist about the same hori- 

 zontal pressure as a thick top bar threeinches and a half square' although it contains little more than half the 

 timber. It is necessary that the lower bars of a field or fold gate should be sufficiently close to prevent 

 pigs, lambs, &c. from getting through ; but the distances between the upper bars should be greater, that 

 it may be constructed without either unnecessary wood or weight. In order, therefore, to arrange the 

 bars so that the increase of their distances may be uniform, the following rule may be serviceable : " The 

 height between the bottom bar and the top bar being given, the position of the other four bars, or for any 

 other number of bars, may be found ; thus, suppose a 6 the given height, to which the width of an inter- 

 mediate bar is added, one half on the 

 top bar, and the other half on the hot. 

 torn bar. One bar must always be 

 exactly in the middle between these 

 two, as at c, to which the braces, at 

 their crossing, are to be bolted. In 

 this design another bar is required 

 ' between a and c, and two bars be- 



tween c and b; that is, the whole 



2s distance, a b, is to be divided into five 



'>.^l parts, in a regular progression to each 



'^^ ^ other. Draw any line, a rf, and from 



" 'n -/'^. Of set off, of any length, five equal 



~---.,*^^ ^N^ divisions; from the second division 



i '~~~.!""-V^. draw a line through c, in the direc- 



494 



a- 



ds:. ^ i-- 



tion e, and from the fifth division 

 if-Z rr-". -v.^> 5.w a. c draw a line through *, also in the 

 * direction e, where the two lines will 



cross; then from the division 1, 3, 

 and 4, draw other lines to e, the point last found, and where these lines cross, the line a b will be the 

 position of the centres of the breadth of the other bars. From the centre of each bar, thus found, mark 

 off half the length of each mortice, and whether the rails be of the same width as the mortices, or tenoned 

 with an equal shoulder on their upper and lower edges, they will be all in a regular progression ; or, in 

 numbers, if the distance a 6 be divided into 110 equal parts ; 



The First distance from B will be 16 of those parts 

 Second - - - . 18 - - - 



Third 21 - - - . J }- 110 



Fourth - - - . 25 - . 



Fifth 30 - . - - } ^ -^ 



The progressive differences between the distances being 2, 3, 4, and 5, the three first being equal to the 

 two last, and the whole equal to one hundred and ten. But if adjusted in the proportion of the followmg 

 numbers, the whole height A B, being divided into thirty equal parts, the bars at the bottom of the 

 gate will be a little closer : 



The First distance - - - - - - 4 " 



Second 5 



- 5} 15 n 

 ^^ Third .--..... eJ I 30 



Fifth 8, 



These numbers have one as a common difference. If these rails have shoulders, and are pinned so as to 

 draw them close to the head and heel, they will be better than without shoulders. The pins should not 

 be exactly in the middle of the breadth of the head and heel, but nearer the inner edge, that the piece of 

 wood between the pin-hole and the end of the rails may not be so liable to split out. 



3081. " On the hanging of gates. When gates are hung to open one way only, their heels and heads 

 generally rest against the hanging and falling post, and are about six inches longer than the opening ; but 

 when they are hung according to this design, gates may be made one foot shorter, or six inches less than 

 the opening ; and, consequently, they are lighter, stronger, and less expensive. The heel may be three 

 inches and a half from the hanging-post, and the head two inches and a half from the falling post. When 

 the two hooks in the hanging-post are placed in the same perpendicular line, a gate, like a door, will rest 

 in any position to which it may be opened ; but in order that a gate may shut itself when thrown ppen, 

 the hook must not be in the same perpendicular line, and the farther they are out of it, the greater will be 

 the force with which the gate will close. The following is a method of fixing the hooks and eyes, or 

 thimbles, to answer this purpose : Supposing the hanging-post to be set perpendicular, and that on^ side 

 or face of the gate is intended to be in a line with one side of the posts, as shown in the engraving, t'le 

 centre of the upper hook may be two inches and a half from the inside, and one inch from the face of the 

 posit. The centre of the eye, or thimble, for the upper hook, may be one inch from the heel, and one inch 

 frolfn the face of the gate. The centre of the lower hook may be an inch and a half from the inside, and 

 half an inch from the face of the post. The eye for the lower hook may be two inches from the heel, and half 

 an inch from the face, of the gate. The best way of fixing the hooks to wooden posts, is to have shoulders 

 to keep them at the proper distance, and a screw and nut on the end which is to go into the post, to which 

 they should be tightly screwed. The eyes should have straps to go on each side of the heel, and along 

 the bottom and top rails of the gate. The straps for the bottom eye may be about six inches long, with 

 two holes for bolts ; one of the bolts to go through the middle of the heel, and the other through the bottom 

 rail and brace. The straps to the top eye may be nine inches long, with three holes for bolts. Blocks 

 being fitted in between the straps and the bars, the nuts are then screwed on the bolts. Eyes of this 

 description, which answered very well, have been made of cast iron ; the pins and screws of the hooks 

 were of wrought iron, the other part cast The position of a plane passing through the centre of each hook, 

 is shown in the engraving {fig 494.), by the dotted line A B on the plan. If the gate was opened to B, it 



