MECHANICS AND USEFUL ARTS. 97 



NEW MODE OF PRESERVING FRESH FRUITS. 



Dissolve gutta-percha in sulphurct of carbon. The liquid separates into 

 three layers, the upper of which contains mucilaginous matters, and the 

 lower earthy compounds and other impurities; the middle layer is perfectly 

 limpid, and contains the pure gutta-percha. Separate this from the others 

 by a siphon. Gather the fruits rather before complete ripeness; dry and 

 brush them ; dip them in spirits of wine ; then two or three times in the 

 gutta-percha liquid ; they may then be kept in a box or closet, the tempera- 

 ture of which must not exceed 50 Fahr. When the fruit is to be eaten, the 

 coating may be peeled off, or washed off with a little spirits of wine; and, 

 notwithstanding time and journeys, the fruit will be found to have preserved 

 its taste and perfume, as though it were perfectly fresh. Cosmos. 



UNIVERSAL PRINTING-PRESS. 



A press adapted to all kinds of printing, has recently been patented by M. 

 Silberman, of Paris, which is thus described in the British Engineer and 

 Arcli. Journal for December ]S~8. 



Pascal's law is this: "'Whatever be the amount of pressure brought to 

 bear upon any point in a contained fluid mass (whether the fluid be a liquid 

 or gas), the pressure is distributed with perfect and entire equality among all 

 parts of the mass, and consequently with perfect equality over all parts of 

 the surface of the vessel which contains the mass;" so that if the vessel, or 

 a portion of it, is pliable and elastic, it will communicate the same pressure 

 it receives to paper, cloth, or any other similar substance, laid upon an un- 

 yielding engraved surface. And the invention consists in printing by thus 

 applying the pressure of a fluid to a yielding surface laid against an unyield- 

 ing engraved surface; and this, whether the surface printed be that of the 

 vessel itself, which thus becomes the press, or whether it be communicated 

 to another interposed yielding surface, from the pliable and clastic side of the 

 vessel, so as to print, on any kind of material, plane, curved, or angular 

 surfaces. 



The application of this principle to the peripheric printing of globes, and 

 of vessels of glass and earthenware, is the subject of a separate paper. At 

 present let us consider merely its application to pi'inting upon plane surfaces, 

 as well as the different modifications it admits of, so as to suit the different 

 kinds of printing; and lastly, of its peculiar advantages over other methods. 



The following are some of the methods in use for the practical application 

 of the principle : 



1. A strong, shallow basin of tough metal is required, with a triple stop- 

 cock at bottom, admitting at pleasure the sort of fluid intended to be used, 

 whether it be atmospheric air, steam, or (when great pressure is required) 

 water, with hydraulic pressure. This basin is filled Avith water, and covered 

 by a tympan formed of a sheet, or of several sheets thick, of caoutchouc, 

 firmly clasped at the edges in an iron frame. A movable plate of iron, 

 strengthened by stays, is attached by strong hinges to one of the edges of 

 the tympan frame. This plate, when shut down upon the surface of the tym- 

 pan, forms the unyielding portion of the press, and supports the engraved 

 plate against the substance intended to be printed, which receives, by means 

 of the tympan, the pressure produced upon the water at the bottom of the 

 basin. 



In order to retain this plate firmly in its place upon the tympan, its edges, as 



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