Fig. 12.
I have quite recently had a mould constructed for me by Mr. Becker,[42] and yesterday (November 16, 1865) made with it an experiment which, on account of the ease with which it may be performed, will interest all those who care about exhibiting in a striking and instructive manner the effects of regelation. The mould is shown in fig. 12. It consists of two pieces of cast iron, A B C and D F G, slightly wedge-shaped and held together by the iron rectangle R E which is slipped over them. The inner face of A B C is shown in fig. 13. In it is hollowed out a semiring M N, with a semicylindrical passage O leading into it. The inner face of D F G is similarly hollowed out, so that when both faces are placed together, as in fig. 12, they enclose a ring 4 inches in external diameter, from M to N, and ¾ of an inch in thickness, with the passage O, 1 inch in diameter, into which fits the polished iron plug P. At q and r, fig. 13, are little pins which, fitting into holes corresponding to them, keep the slabs A B C and D F G from sliding over each other.
Fig. 13.
Fig. 14.
The mould being first cooled by placing it for a short time in a mixture of ice and water, fragments of ice are stuffed into the orifice O and driven down with a hammer by means of the plug P. The bruised and broken ice separates at x, one portion going to the right, the other to the left. Driving the ice thus into the mould, piece after piece, it is finally filled. By removing the rectangle R E, the two halves of the mould are then separated, and a perfect ring of ice is found within. Two such rings soldered by regelation at a are shown in fig. 14. It would be easy thus to construct a chain of ice. An hydraulic press may of course be employed in this experiment, but it is not necessary; with the hammer and plug beautiful rings of ice are easily obtained by the regelation of the crushed fragments.
I have now to add the description of an experiment which suggested itself to my ingenious friend Mr. Duppa, when he saw the ice-rings just referred to, and which was actually executed by him yesterday (the 16th) in the laboratory of the Royal Institution. Pouring a quantity of plaster of paris into a proper vessel, an ice-ring was laid upon the substance, an additional quantity of the cement being then poured over the ring. The plaster ‘set,’ enclosing the ring within it: the ring soon melted, leaving its perfect matrix behind. The mould was permitted to dry, and, molten lead being poured into the space previously occupied by the ice, a leaden ring was produced. Now ice can be moulded into any shape: statuettes, vases, flowers, and innumerable other ornaments can be formed from it. These enclosed in cement, in the manner suggested by Mr. Duppa, remain intact sufficiently long to enable the cement to set around them; they afterwards melt and disappear, leaving behind them perfect plaster moulds, from which casts can be taken.