146 Progress of Invention. 



chlorate of potash, and, as he believes, a compound of hyposul- 

 phurous acid with soda, ammonia, oxide, and suboxide of copper. 

 He obtains this compound by dividing a solution of copper into 

 two equal parts, supersaturating one with ammonia, and the other 

 with hyposulphite of soda; then mixing the two solutions, and 

 stirring briskly. One part of the violet coloured powder which 

 precipitates is mixed with two parts of the chlorate of potash, a 

 little powdered glass being added. This composition detonates by 

 percussion, and ignites when rubbed in a mortar. It is not soluble 

 in water, nor is it hydroscopic ; but even when made with moist 

 chlorate of potash and solution of gum its cohesion is so imperfect, 

 that it often crumbles off the matches when they are rubbed. It is 

 also liable to the objection of requiring no particular kind of 

 surface for ignition, which involves the danger of causing confla- 

 grations. Dr. Hierpe uses for the match heads four to six parts 

 chlorate of potash, two parts bichromate of potash, two parts ferric 

 oxide, and three parts strong glue. The ferric oxide may be 

 replaced by oxide of lead, or of manganese. Matches made with 

 this composition will ignite only on a surface coated with a mixture 

 containing twenty parts sulphide of antimony, two to four parts 

 bichromate of potash, four to six parts oxide of iron, lead, or man- 

 ganese, two parts glass powder, and two to three parts strong 

 glue or gum. 



Gas Engines. — It is one of the advantages of modern progress 

 that many operations formerly performed by the painful efforts of 

 man and animals, are now effected with much greater ease and 

 economy by means of power obtained from other sources. A 

 striking illustration of this is found in the use of portable steam- 

 engines in public works. Perhaps a still more striking is the 

 utilization of the enormous water power* available in Paris for the 

 lifting of heavy weights to great heights, and in the employment 

 of Lenoir's gas engine for a similar purpose. It is evident that for 

 intermittent efforts the steam-engine is far from economical, on 

 account of the necessity of keeping up the steam during the 

 intervals of inaction. This objection does not hold with the gas 

 engine. It consumes nothing when it is not actually at work, it 

 is, besides, very portable, and the gas, as also the water for refri- 

 geration, it requires may be had almost anywhere. It is not 

 surprising, therefore, that it is coming into use in France in building 

 operations, any defects it may possess being more than counter- 

 balanced by the advantages it offers. 



The Electric Light Adapted to Use in Mines. — "Notwith- 

 standing the excellence of Davy's lamp, especially in its improved 

 forms, the most lamentable accidents are of constant recurrence in 

 mines ; sometimes, no doubt, they are due to imperfection in the lamp, 

 but most usually to imprudence in the miners. The use of electricity, 

 as a means of illumination, would remove all danger of this kind ; 

 but hitherto its light, though very intense, was useless for ordinary 

 purposes on account of the impossibility of rendering it sufficiently 

 diffused ; and, besides, its arrangements were complicated, on 

 account of charcoal points being necessary. These objections seem 



