Dr Kosmann of Breslau has designed a safety cartridge for use in fiery mines, but it has not yet passed the ordeal of practical employment. It depends for its efficiency upon the sudden evolution of a large volume of hydrogen gas, which is brought about by the action of dilute acid upon finely divided zinc. The ‘cartridge’ consists of a glass cylinder pinched into a narrow tube at the centre, so that interiorly it is divided into two compartments. One of these contains the powdered zinc, and the other the dilute acid, the passage between them being closed by a rubber cork. The borehole into which it is inserted is first of all made gas-tight by a lining of clay; then the cartridge is put in position, with an iron rod in connection with it so placed that, when struck with a hammer from the outside of the hole, it will drive in the rubber cork, and so bring the acid into contact with the zinc. We shall be interested to hear how the method answers in practice. JACK, THE BUSHRANGER. AN AUSTRALIAN REMINISCENCE. Reading in your _Journal_ (writes a correspondent) an article headed, ‘A Bushranger Interviewed,’ recalls to my memory a strange incident which occurred some years ago to my own brother, when on his way from Sydney to the gold-fields, and for the accuracy of which I can vouch. At the time of his arrival in Australia, the country was in a state of panic: a reign of terror existed, caused by the daring outrages committed on parties on the journey to and from the diggings. Robbery with violence, escorts shot down, and large consignments of gold carried off, were of daily occurrence. The bush was infested by a gang of desperate bushrangers, whose leader, under the cognomen of ‘Jack,’ seemed to bear a charmed life. For years he had evaded all the efforts made to capture him, though the military scoured the bush. No sooner was an outrage perpetrated, than all trace of the perpetrators was lost, as if the ground had swallowed them. He had a perfect knowledge of the most secret movements of the parties he attacked. He seemed ubiquitous, outrages occurring in such rapid succession and far apart. Such an air of mystery hung about him, that a superstitious feeling mingled with the moral terror he inspired. He was represented by some persons who had seen him, as a fine powerful-looking man, with nothing forbidding in his appearance.