232 Progress of Invention. 



suitable for excluding the air. A compound possessing the good 

 qualities of iron, and not acted on by the atmosphere, is likely to 

 prove invaluable. Alloys of copper and manganese may be ob- 

 tained in a similar way, and some of them possess very important 



properties. Generation of Seat by friction. — This is a subject 



which is exciting some interest in France at present ; and although, 

 generally speaking, the production of motion by means of heat, 

 and the change of this motion back again into heat, is too cir- 

 cuitous a mode of proceeding to be economical, there may be 

 circumstances in which it would be preferable to any of the ordi- 

 nary methods of obtaining heat. M. Pelon's contrivance for the 

 purpose consists of a truncated cone of wood, covered with hemp, 

 and revolving within a similar cone of copper, in such a way that 

 considerable friction arises from the rubbing of the hemp against 

 the copper, while at the same time this friction is prevented from 

 becoming inconveniently great by a lubrication which is effected 

 by an ingenious application of centrifugal force. The whole is 

 placed in a metallic casing, within which the air to be heated is 

 made to circulate slowly. A large apartment is said to have been 

 effectively and very rapidly warmed by this apparatus with a 

 trifling expenditure of force ; and it seems applicable to the heat- 

 ing of railway and other carriages, the cone of wood being kept in 



motion by the revolution of the carriage wheels. Evaporation by 



Mechanical Means. — The evaporation of solutions for the produc- 

 tion of crystals, etc., constitutes a serious item of expense. It is 

 found that this may be greatly lessened by a concentration or pre- 

 paratory evaporation effected by mechanical means. For this 

 purpose horizontal, cylinders are placed, one at the top and the 

 other at the bottom of a frame, the lower cylinder being im- 

 mersed in the liquid to be evaporated. Over these cylinders are 

 stretched a number of vulcanized India rubber cords ; and when 

 the upper roller is turned by the hand, or by other suitable means, 

 these ascend, carrying up with them portions of the fluid, and 

 bringing them into contact with the air, which — especially under 

 exposure to the sun — causes large quantities of moisture to be 

 dissipated. The effect thus produced is found much cheaper 

 than when obtained by the agency of heat in the usual way. 



—Artificial Leather. — This is now formed by mixing cuttings 



of leather with an equal bulk of solution of caoutchouc, spread- 

 ing the mixture, to a desired thickness, on plates of metal, 

 and when the outer surface has become sufficiently hard, passing 

 the whole between rollers, then drying at 90° Fahr. The artificial 

 product thus obtained may be pressed into any desired shape in 

 moulds, and used for any of the purposes to which leather is 



applied ; it may even be vulcanized, by a very simple process. 



Cocaine. — This substance, which is not long discovered, is one of 

 that class to which theine, caffeine, etc., belong. It is obtained 

 from coca, the leaves of the Eryihroxylon coca, a South American 

 shrub, which are chewed very generally by the inhabitants of those 

 regions where it grows, and is remarkable, not only for enabling 

 persons to endure the want of food, but for being in a surprising 



