54 ANNUAL OF SCIENTIFIC DISCOVERY. 



dissolve, yielding a liquid which is thicker than benzine, and may be 

 obtained very clear by filtration and rest. The residue may be sepa- 

 rated by straining, and will furnish an excellent waterproof composi- 

 tion. As for the liquid itself, it incorporates easily with all fixed or 

 volatile oils. It dries very fast, and does not shine, unless mixed Avith 

 resinous varnishes. It is extremely flexible, may be spread in very 

 thin layers, and remains unaltered under the influence of air and 

 light. It may be employed to varnish geographical maps of prints, 

 because it does not affect the whiteness of the paper, does not reflect 

 light disagreeably, as resinous varnishes do; and is not subject to 

 crack, or come off in scales. It may be used to fix black-chalk or 

 pencil drawings ; and unsized paper, when covered with this varnish, 

 may be written on with ink. 



NEW APPLICATIONS OF GUN-COTTON. 



The London Chemical News refers approvingly to a patent re- 

 cently obtained in England by S. Branwell and A. Rollason, for 

 obtaining new and peculiar products from mixtures of gun-cotton 

 (pyroxyline) with various substances. 



In order to obtain cheap gun-cotton, the patentees state it may 

 be made of rags instead of new cotton. It is first dissolved in any 

 of its solvents, such as ether and alcohol, and becomes collodion. To 

 this is now added any of the purest animal and vegetable oils, and it 

 forms the new liquid which is to be used as a cement and vehicle. 

 By adding to it gums and resins a cement is formed, which may be 

 rolled out into sheets and stamped in dies into cups, fancy boxes, and 

 various other articles. The oxyd of copper imparts a green color to 

 it, and the chloride of lime added renders it uninflammable. The 

 addition of fine flax fibre or the flocks of wool render it strong and 

 flexible. It is stated to be an excellent compound for taking casts 

 required for the purposes of dentistry, the models of jewellers, and 

 other articles requiring sharp and smooth edges and sides. 



The collodion oil-liquid, when very thin, may also be employed as 

 a varnish for pictures, prints, etc. 



THE PNEUMATIC DISPATCH. 



For some months past (see Annual of Sci. Dis., 1861), a Pneu- 

 matic Dispatch Company has been in operation in London, pipes of 

 a few inches in diameter being laid, through which small parcels 

 were sent to various parts of the city. The company, finding the 

 system to work well, have decided to enlarge the tubes to a height of 

 two feet nine inches and to a width of two feet six inches, and ulti- 

 mately extend their system throughout the whole metropolis. Pre- 

 liminary to this, the following experimental trials have been insti- 

 tuted, for the purpose of effectually testing the project, on a vacant 

 piece of ground adjacent to London. A quarter of a mile of the tubing 

 has been laid down ; various irregular curves and gradients being 

 introduced, to show that hills and valleys would not prevent the 

 effective working of the system. Under a temporary shed, a high- 

 pressure steam-engine of thirty horse power, having its cylinder 



