MECHANICS AND USEFUL ARTS. 99 



a case, which gives facility for shaking the mould well when the plas- 

 ter is poured, so as to drive it well into the crevices. The plaster 

 should be fine ; and, in order that it may harden and set quickly, 

 about half an ounce of alum should be added to each pint of water 

 used in mixing it. Before using the mould, it should be carefully 

 oiled. Great care is required in mixing the plaster and watching it 

 when in the mould, for if it be allowed to remain long enough to 

 heat, the mould is destroyed. Sheffield (England} Independent. 



^ 



DISTILLATION OF SALT WATER. 



MANY machines have been invented for the purpose of distilling 

 fresh water from salt water, but hitherto there has always been some 

 objection to each and all of these contrivances. But the British gov- 

 ernment seem to have satisfied themselves that a Mr. Grant has invented 

 something which will answer the purpose, for they have lately pro- 

 vided several of their vessels of war with his machine. He calls it 

 " The Distilling and Cooking Galley." By some improvements made 

 since the first invention, the quantity of fresh water obtained by the 

 distillation of salt water during the time it is necessary to keep the 

 galley-fires lighted for the purpose of cooking will, on the average, 

 supply every person on board the vessel with one gallon of distilled 

 water every day. This water is preferred to that usually supplied to 

 ships for drinking and culinary purposes; and, as it passes imme- 

 diately from the condenser to the water-tanks, it enters the latter at 

 the temperature of the sea. In a few hours the simple motion of the 

 ship, without any chemical means, completely aerates the water, and 

 removes the vapid flavor which characterizes distilled water. Experi- 

 ments are in progress with a view of imparting at the moment of dis- 

 tillation the oxygen of which the water is deprived in the process, 

 and thus giving to it the briskness of spring water. This is proposed 

 to be effected by passing a current of electricity through the particles 

 of water by means of a very simple, self-acting apparatus. Abridged 

 from the London Times. 



FENCE FOR FIELDS LIABLE TO BE OVERFLOWED. 



THIS simple invention is patented by Wm. Miller, of Pennsylvania. 

 Two posts should be taken, about 7 inches square, and 5 feet long, 

 and sunk 3 feet in the ground. A triangular mortise, 2 inches deep, 

 4 high, and 5 wide, must be cut in the side of the posts 3 or 4 inches 

 from the ground, and a shallow notch in the form of a V must also be 

 cut in the top of the posts, and rails, corres} onding in form with this 

 notch, are laid on them. The lower rail i., fitted into the mortise by 

 making the ends round, like gudgeons, which are to be inserted in the 

 inorti-f. cadi gudgeon being about 2-1- inches in diameter, and of any 

 length. The boards being tla-n nailed on the side of the rails against 

 which the water flows, whenever the flood strikes them, the round 

 gudgeons will slide up the sloping sides of the mortise, and the upper 

 rails will rise out of the notches, so that the entire pannel will fall flat 

 upon the ground, being secured by the gudgeons. After the flood has 



