This convenient little implement is made of cast iron, and is so contrived that it may be folded into a very small space, as shown in Fig. 2, or extended for use as shown in Fig. 1. The jaws, F G, are pivoted together at C, the head of the pivot sliding in a rib of a slot, E, in the foot plate. The jaws have grooves in their upper surfaces, as shown in Fig. 1, the groove of one being placed further back than the groove ofthe other. The support, D, of the foot plate, is pivoted to the foot plate, and folds down, as shown in Fig. 2, when the jaws are thrust back ; thus making a very compact arrangement for carrying in the pocket or carpet bag. The folding and unfolding of the support, D, is effected by lugs cast upon the portion of the support, D, which passes between the jaws and the loot plate. These lugs lie directly under the points of the jaws indicated by the letters A and B, Fig. 2. The outer end of the groove which lies nearest to the foot plate, Fig. 1, striking against the lug which plays in that groove folds down the support when the jaws are thrust in ; while the inner end of the groove in the other jaw, striking thelug which slides in that groove, unfolds it when the jaws are thrust out. The jaws slide in ways which force them together when they are thrust in, and open them when they are thrust out.This implement will draw any sized boot from a lady's gaiter to the largest men's wear. Its convenience to travellers, as well as others, is obvious.Patented through the Scientific American Patent Agency, Oct. 29,1867, by Albert P. Seymour, of Hecla Works, Oneida county, N. Y., who may be addressed for the entire right for k the .United States or for State s rights. The East Hiyer Bridget We learn from the Brooklyn Times that the construction of the caisson which is to be sunk at the base of the Brooklyn tower of the East River Bridge, .. is begun, and is now well under . way. Colonel Wm. H. Paine is present at Messrs. Webb's yard every day, superintending the work on behalf of the Bridge Company. It is expected that the caisson will be ready to launch some time in March. It will then be floated to the location of the Brooklyn foundation of the tower. The river shore will be dredged out to low water line, and the caisson floated into its position on a high tide; on |: the water receding, it will be *_ anchored or " seated," and exec-Is vating to sink it -the required S depth will be carried on in its interior. Through the roof will be six shafts, or funnels, made of half-inch boiler iron. The two suoply shafts through which the workmen descend and ascend, and by which the excavated soil is removed, will be twenty-one inches in diameter each. Each of the two air shafts, by which air is supplied to the workmen, is-forty-two inches in diameter. Each of the two water shafts, in which the water oozing through the soil will be conducted, so as to keep clear of the workmen, is seven feet square. On top of this caisson will be piled timber to the hight of fifteen feet, and the whole mass filled in with concrete ; and on this bed of wood and stone will be placed the masonry for the towers. The caisson is in shape a parallelogram, 168 feet long and 102 feet wide on the outside, and is about 15 feet high. The sides are V-shaped, the bottom being eight inches thick, and the top eight feet three inches, and ten feet high, and the roof, which rests on these sides, is five feet thick. The whole is constructed with yellow pine a foot square, with the seams caulked. Between the outside layers of timber is a sheathing or layer of tin, between two of felt, intended to prevent the atmosphere from working into the interior of the caisson. The sharp edges of the structure, are to facilitate the sinking of the box thirty feet beneath low tide level, and accordingly this portion is strongly made. The first layer of timber is of oak; on this is bolted a cast-iron shoe, eight inches wide, oval on its face, being three inches thick in the center. Around the shoe is placed an armor of boiler iron, extending three feet above the shoe, on both sides of the wall, the whole strengthened by heavy angle irons on the interior, sixteen feet long. As the pressure of air on the caisson will increase as it sinks, it is estimated that the atmosphere resting on the surface will vary from 18,000 tuns to 40,000 tuns. Consequently, careful and accurate calculation is made to give strength to the box. The timbers are all bolted together, perpendicularly, horizontally, and diagonally, with the heaviest and longest bolts ever used. These bolts are, on an average, eighteen inches apart throughout the structure, and the ends are made air-tight by rubber washers. The immense number of bolts may be imagined, when it is expected that one hundred tuns of them will be used. The interior of the caisson will be a room one hundred and sixty-six feet long, one hundred feet wide, and nine feet high. There will be about one million five hundred thousand lineal feet of timber used in constructing the caisson, and when ready for launching it will weigh three thousand tuns. In order to launch it, there will be seven ways or keels underneath, and a watertight compartment, or air-chamber, in the interior, thirty-eight feet wide, extending lengthwise. In addition to this there are ten heavy supporting frames to sustain the roof. As regards the negotiations lor obtaining the site for the tower on the Brooklyn side, it appears that they have so far made but little progress. This tower will, it is understood, be built in the third or upper slip of the Pulton ferry. The Ferry Company lease their ferry property from the City of New York, and the Commissioners of the Sinking Fund of that city are vested with the power of leasing and selling public property. The Brooklyn Eagle states that when negotiations were opened by the Bridge Company to obtain possession of the- upper slip and section of the adjacent land, the Sinking Fund Commissioners reierred the matter to a Commission of Estimate and Assessment, consisting of Wilson G. Hunt, and Thomas R. Agnew, who have not yet made their report. It is understood, however, that this will be forthcoming without much further delay, after which the preparations for the reception of the caisson will be at once proceeded with. the Force of Contraction Applied to Repairs of Buildings. The force of contraction is equal to that of expansion, and quite as irresistible. Its immense power was strikingly illustrated some years since in Paris. T'he two sides of a large building, the "Conservatoire des Arts et Metiers," having been pressed out by the spreading ot the arched ceilings and the immense weights supported by the floors, M. Molard undertook to remedy the evil by boring holes in the wall at the base of the vaulted ceilings, and opposite to each other, through which strong iron rods were introduced, so as to cross the interior of the building from one side to the other. On the projecting ends of the bars on the outside of the building were placed strong iron plates, which were screwed, by means of nuts, tightly against the walls. The rods were then heated by means of rows of lamps placed under every alternate bar, and being lengthened by the expansion, the nuts and plates were pushed out to the distance of an inch or more beyond the walls. While in this condition, the nuts were screwed a .second time tightly against the wall. The lamps were then extinguished, and the rods, contracting as they cooled, drew the walls together with a force almost irresistible, and to a distance as great as that to which they had been lengthened by expansion. These bars being then left in their new position, the alternate bars, which had remained unheated, and by the contraction of the others had been also made to project beyond the walls, were again tightly screwed against the building. These were in turn expanded and lengthened by the application of the lighted lamps, and once more screwed up tightly against the walls. The lamps were then extinguished, and by the contraction of the second set of bars the walls were drawn still further toward each other. These were then left, in turn, to hold the building in its new position, and the first set of bars a second time brought into requisition. And thus the process was continued until the walls were drawn into their proper vertical position; and the bars being left in their places, they have remained firm and upright ever since. In this manner a fore was exerted which the power ot man could scarcely have applied by any other means. The same process has since been applied to the restoration of other buildings which were threatening to fall.—Pynclicm's Chemical Forces. Air in Illmminatliig Gas. Professors Silliman and Wurta have been investigating the effects of atmospheric air upon the illuminating power of gas, with, according to the Chemical News, the following results: " For any quantity of air less than 5 per cent, mixed with gas, the loss in candle power due to the addition of each 1 per cent, is a little over six tenths of a candle (0'611 exactly) ; above that quantity the ratio of loss falls to half candle power for each additional 1 per cent up to about 12 per cent of air ; above which, up to 5 per cent, the loss in illuminating power is nearly four tenths of a candle for each 1 per cent of air added to the gas. With less than one fourth of atmospheric air, not quite 15 per cent of the total illuminating power remains, and with between 30 and 40 per cent, it totally disappears. A BELGIAN report on the preservation of telegraph posts decides that chloride of zinc is the best and cheapest agency to employ, though it does not work equally well in all soils.