Book IV. 



GATES, STILES, AND BRIDGES. 



505 



509 



3107. Parker's sympathetic park-gate {Jig. 510.) is an ingenious contrivance, by which, on the approach 

 of a carriage, the gate opens apparently by its own volition, and closes again after the carriage has passed 

 through, without any apparent cause. The manner in which this extraordinary effect is intended tobe pro- 

 duced L by small plates let into the ground at short distances from the gate, and when the carriage wheels 

 roll over them, they are made to descend like a weighing machine, and to act upon certain levers concealed 



in a trunk under the road, by means of which a toothed wheel is made to revolve, and to turn a toothed 

 pinion affixed to the swinging-post or axle of the gate, and hence to throw it open or close it (Newton's 

 Journal, vol. xiv. p. 225.) In an agricultural point of view, this gate is of no use ; but as a curiosity it is 

 worth noticing, and perhaps in the drives or ridings in somt pleasure-grounds and parks it might be worth 

 executing. In England it might save the tax on a groom, and in America and Australia it might be as 

 good as a helper, which, for such aids as opening gates are not very easy to be found. 



3108. Stiles are contrivances for man to pass over or through fences, without the risk 



of even permitting the larger quadrupeds to accompany or follow lum. There are many 



forms perfectly well known every where: as by steps over a wall ; by a zig-zag passage, 



formed by stakes, through a hedge or paling ; a turning-bar or turnstile, &c. 



31C9. The stile of falling bars (fig. 511.) is chiefly used in pleasure-grounds, or between paddocks ; 



511 



it consists of bars, light at one end (a) and heavy at the other (ft), with concealed joints or pivots, in an 

 upright post (c) placed nearer one end of the bars than the other. Then, while the weight of the short 

 ends of the bars keeps them in a fencible position, a slight pressure on the other end will form a passage 

 (</) which any one may easily step across. 



31 10. Bridges are frequently required on estates and farms, for crossing ditches and 

 water-courses. They arc generally large stone conduits or barrel-drains ; or in the case 



