Economy of Machinery and Manufactures. 117 



*'A beautiful mode of representing small branches of the most delicate vegetable 

 productions in bronze, has been employed by M. Chantrey. A small sprig of the 

 fir tree, a branch of holly, a curled leaf of broccoli, a vine leaf and tendrils, or any 

 other vegetable production, is suspended by one end, in a cylinder of paper, which 

 is placed for support within a similarly formed tin case : the finest river silt, care- 

 fully separated from all the coarser particles and mixed with water, so as to have 

 the consistency of cream, is poured into the paper cylinder, by small portions at a 

 time, carefully shaking the plant a little each time, in order that every vein and curl 

 in the leaf may be covered, and that no bubbles of air may be left. The plant and 

 mould are now left to dry, and the yielding nature of the paper allows the loamy 

 coating to shrink from the outside. When this is dry, it is surrounded by a coarser 

 substance ; and finally, we have the twig, with all its leaves, imbedded in a perfect 

 mould. This mould is carefully dried, and then gradually heated to a red heat. At 

 the ends of some of the leaves or shoots, wires have been left to afford air holes by 

 their removal, and in this state of strong ignition, a stream of air is directed into the 

 hole formed by the end of the branch. The consequence is, that the wood and 

 leaves, which had been turned into charcoal by the fire, are now converted into 

 carbonic acid by the current of air, and after some time the whole of the solid mat- 

 ter of which the plant consisted is completely removed, leaving a hollow mould, 

 bearing on its interior all the minutest traces of its late vegetable occupant. When 

 this process is completed, the mould being still kept at nearly a red heat, receives 

 the fluid metal, which by its weight diives out, through the holes, any air, which, 

 at that high temperature, may remain behind."* 



Of ^^ copying by moulding" many examples are cited by the au- 

 thor, illustrative of the methods and advantages of this branch of the 

 arts, from the humble brick and tile, to the costly mouldings employ- 

 ed by the jewellers, and the curiously embossed work upon porcelain. 

 Many of the splendid dwellings in our own metropolitan cities, are 

 indebted to this art, for the beautiful cornices, which ornament their 

 apartments. 



" Copying ly stamping" comprises the modes of coining and stri- 

 king medals, making ornaments for military accoutrements, Stc. Sic. 



It would exceed the limits of this paper to make further extracts 

 from this part of the work, but the author treats, successively, of 

 copying by punching, of wire drawing, of rose engine turning, of 

 copying dies, of the pentegraph, and finally of copying by stereotype 

 plates, which are themselves castings, made in moulds formed by 

 movable types, " those obedient messengers of the most opposite 

 thoughts and conflicting theories" — all showing that the principle of 

 copying is an important auxiliary to cheapness and uniformity in the 

 mechanic arts. 



Having thus glanced at the principles, which impel and regulate 

 mechanical operations, the author proceeds to consider the economy, 

 which governs the application of machinery, and the polity, or in- 



* The author does not inform us in what way the mould may be made available 

 for more than one casting. 



