474 Progress of Invention. 



placed in the flue of an ordinary furnace,' and after having expanded 

 in the cylinder, and thus actuated the piston, it is transmitted back to 

 the heating tubes, the caloric it still retains being by this means 

 economized. The heating power of the tubes is augmented by filling 

 them with scraps of metal which render them magazines of heat, 

 absorbing it when it would be in excess, on account of connection 

 with the cylinder having being cut off during expansion, and giving 

 it out at other times. A still better engine of this description has 

 been invented by Mr. Wenham. It is remarkable for simplicity, 

 economy, and compactness. The expansion of air driven through 

 a small furnace and a very mild explosion of carbonic oxide, supplies 

 a perfectly safe motive power. 



Purification OF Sulphuric acid. — Sulphuric acid, from the mode 

 of its manufacture, is very frequently found to contain nitric acid, 

 which though small in quantity, is difficult of separation, and if unre- 

 rnoved is often very inconvenient. It has been found, that sulphuric 

 acid may be completely freed from nitric, so as to afford no indication 

 of its presence, by means of freshly calcined and pulverized wood 

 charcoal, which may be removed by filtration. 



Production of Caloric by Magnetism. — It has been ascertained 

 that the rapid rotations of a magnet, or what is more effective, of a 

 compound magnet consisting of several magnetized bars, will afford 

 caloric. The effect is due to the prevention of motion which the 

 magnet tends to produce. The experiment may be made, by placing 

 above the poles of a magnet, which is capable of revolving on a verti- 

 cal axis with its poles upwards at the rate of fifteen or twenty times 

 a second, a small copper plate of a circular form, and about half a 

 millimetre thick, and putting upon this plate a flat bottomed flask 

 of considerable capacity, and having fixed in its neck, by a cork, a 

 tube in the form of an S with a little water in its lower curve 

 which is within the flask ; the rapid rotations of the magnet heats 

 the air : and this expanding acts on the surface of the water in the 

 tube and causes it to ascend. When a maximum temperature, depen- 

 ding on the velocity of rotation is attained, the water will remain 

 stationary. M. Louis D'Henry, to whom this experiment is due, 

 believes that with a sufficently powerful system of magnets, and a 

 rapid rotation, water in a copper vessel, placed on the copper plate 

 might be made to boil. 



New Substitute for Phosphorus in the Manufacture of Lucifer 

 Matches. — The terrible effects produced by ordinary phosphorus 

 on those who manufacture matches with it, and the obstacles to the 

 introduction generally of amorphorus phosphorus renders a substi- 

 tute for this pernicious material very desirable. Such a substitute 

 is most probably to be found in a mixture recently discovered by 

 M. Bottger. It consists of eight parts ti'ioxide of thallium, and one 

 part penta-sulphuret of antimony : and may be ignited by friction. 



Utilization of the Residues of the Smelting Furnace. — Large 

 quantities of cinders, hitherto incapable of use for any industrial 

 purpose are produced by smelting furnaces. They have been found 

 on examination to consist for the most part of very minute globules 

 of iron. The recovery of this iron will not only be a means of get- 



