50 



ANNUAL OF SCIENTIFIC DISCOVERY. 



high pressures, when confined mechanically, cast-iron, as well as other 

 metals, appears, like liquids, to exert an equal pressure in every direc- 

 tion in which its motion is opposed. Clark's Britannia and Conway 

 Tubular Bridges. 



A NEW METHOD OF OBTAINING ELABORATE METALLIC CASTINGS. 



A NEW method of obtaining elaborate and delicate castings has been 

 devised by Mr. Dircks, of London. The most intricate and curious cast- 

 ings we are acquainted with are those obtained in moulds, from 

 nature's own works, by imbedding a leaf, plant, &c., in a semi-fluid 

 medium, which, when hardened, can be dried and raised to a tempera- 

 ture sufficient to burn the enclosed object to ashes. But, if it were 

 desired to produce, by this method, a casting, as a wreath, bouquet, 

 group of animals, &c., the artist would find himself unable, or else be 

 obliged to make as many separat&jaaouMg a&4jiere were involved parts 

 hi the object to be cast. To^^^thhdtSffi^y^Alr. Dircks employs 

 a laver of wax on a sheet/oc^elass : the wax isGnisteived in the man- 



* -L *^O^^^ -*C7^ x 



ner desired, and a plaster (rast mafteorithe top orj&et engraved wax. 



On slightly warming thfemass, theplaster and wak Ikave its surface 



together, presenting a penecl^Q3pfoj|ni a]$J${jance. ] The plaster is 



now to be heated grad 



like snow into the eart? 



plaster, quite sharp, p 



appearance, even where 



ness. In this way any figure ma; 



X sinks into it 

 now engraved 

 waxed or oily 

 an inch in thick- 

 in sheet wax, and after- 



wards cast in plaster. A metallic casting is then made in the usual 

 manner from the plaster. In order to economize wax, a mixture of 

 stearine, Burgundy pitch, and resin, may be substituted. In this way 

 metallic castings may be obtained, which hi delicacy exceed any before 

 produced. An electrotype may, if desired, be taken from the plaster, 

 instead of a castin. ^London Athenaum. 



INCRUSTATION IN BOILERS. 



DR. BABBIXGTON, of London, has taken out a patent for preventing 

 incrustation by voltaic agency. For iron boilers he recommends a 

 plate of zinc, 16 oz. the square foot, to be attached to one of its edges 

 by solder to the ulterior of the boiler ; and both sides of the plates 

 being left exposed to the action of the iron and water, voltaic agency 

 thus excited is said to have the desired effect. For large boilers, two, 

 three, or more plates may be used, as necessary. 



IMPROVED METHOD OF DRIVING A TILT-HAMMER. 



A NEW invention for the driving of tilt-hammers has recently been 

 introduced into the United States Armory at Springfield, which will be 

 of great importance to every large forging establishment in the country. 

 The old method of driving a tilt-hammer is by a water-wheel to each 

 hammer, or to every two hammers. The necessity of compelling this 

 arises from the fact that if the hammer were driven by a belt, from a 



