The primary object of the device illustrated in the annexed engraving, is to afford a sure and sufficient support to the gate when closed, to prevent the loosening and pernlanent inclination of the hinge post. It also affords a ready means oi opening the gate; and secures its effective latching when closed. On the stile, or upright, A, is a slotted plate, screwed or bolted to the wood, and carrying a stud and roller, B. On the post, C, is a snug, or plate having a double incline, slightly hollowed at the apex to receive the perimeter of the roller, B. A projecting horizontal flange having inclined sides and a notch in the center is for the use of the catch, D, that is a part of the spring, E, which holds the catch in the notch. When the gate is to be opened, the spring, E, is pushed back, thus unlatching the gate and allowing it to swing in either direction. When closed,the roller, B, rests on the snug which then sustains the weight of the gate. It is not necessary that the gate should swing both ways; it may be furnished with this device adapted to suit the exigencies of any case. The device is cheap, easily attached to any swinging gate, and always reliable. Patented through the Scientific American Patent Agency, Dec. 15, 1868, by Benjamin Hendricks, who may be addressed at Huntington, L. I. The New Mode of Firing Gun-Cotton. An interesting practical exhibition of the newly-discovered properties of gun-cotton when fired by concussion, instead of by the direct application of flame or heat, was afforded recently at Woolwich. The huge 36-in. Mallet mortar, weighing 52 tuns, which was placed in the marshes in 1857, and designed to fire a Shell of 2,548 lbs. (empty), has, for some time past, been sinking in its great wooden bed, owing to the gradual decay of the wood. It was thought dangerous to run the risk of its falling upon any visitor by leaving it in this position. But Weights of 52 tuns cannot be moved for nothing. To erect sheers and the necessary appliances for raising the mortar Would have entailed an expenditure estimated at about 50. Under these circumstances, recourse was had to gun-cotton to destroy the bed, and precipitate the fall of the mortar. Four charges of 4 ozs. each, four of 6 ozs., and one of 8 ozs. (total, 48 ozs.) were placed on the wooden bed, and exploded by means of mining fuses charged with detonating composition. The material being rotten was especially unfavorable for the exertion of explosive force for the force had, so to speak, nothing to act against. But what could be done was done. The huge bed was shattered, and particles flew in all directions. The mortar, although it altered its position, refused, however, to fall, being held, to some extent, by a thick wrought-iron screw bolt. The next experiment was made upon this bolt. A one-lb. disk of compressed gun-cotton was tied to the bolt and exploded. The explosion was thus wholly unconfined. Nevertheless the bolt was broken in two places, a result which exceeded the most sanguine anticipations. Still the huge mortar remained in its position. A third operation had, therefore, to be made. This time two 1-lb charges were disposed under the left trunnion, and the 1-lb. charge was so placed as to give the mortar a kick behind. The explosion of these charges completed the work. The monster mortar slowly and gracefully bowed forward and fell to the ground. The gun-cotton had thoroughly done its work, at a cost of 14s. d.~Scientific Review. ------.---------------. fre . ------------- The UJse of Zinc in the Reduction of old Ores. M. D'Heureuse has been for some time experimenting in the use of zinc as a substitute for quicksilver in gold mining. According to the Scientific Review, he now finds that in the amalgamation process only about half the gold is extracted from the rock. Melted zinc appears to take up all the gold, allows slag and rubbish to float at its surface, requires little heat to keep it melted, and from its volatile nature can be dis- tilled in a retort to separate the gold and re-collect the zinc itself. The mode of operating is simply to introduce gradually the gold-bearing rock, in a pulverized state, into a bath of ' melted zinc. This metal immediately attacks and dissolves - nearly every particle of gold, while the debris rise to the surface of the bath, and can be skimmed off. When sal-phurets are present, the rock must be previously roasted. Surely nothing can be more economical and effective than this when plenty of zinc ore is at handi ------------------~+' * ------------------- Sugar from Pumpkins, We condense the following from a Southern cotemporary for the benefit of our readers: i During late years, several more or less successful attempts have been made to introduce into the United States, sugar-producing plants to replace the cane. The beet root and sorghum are among the number, but one of the most valuable, which is cultivated in every cornfield in the Middle States as a side product, has been quite neglected. This plant is no other than the common pumpkin, the Gucurbita pepo of botanists. Its period of harvesting lasts longer than that of the beet, it is easier preserved and its refuse is just as valuable for the feeding of stock. Pumpkins weigh from 50 to 60 pounds; they furnish about 4 per cent of sugar; their contents in juice is 80 per cent. This juice indicates from 10 to 11 on Baume's areometer. The sugar obtained from pumpkins is of a good grain and color. Before refining, it has a slight flavor of melon. The sirup is of a very dark green color, nearly black, and tastes like cane sugar. In Hungary, since the year 1837, several manufactories for making sugar from pumpkins have been in operation. The treatment of this fruit is perfectly identical with that of the beet root, and the machinery used for the purpose the same.