Roburite was also one of the explosives investigated by the committee appointed in September 1889 by the Durham Coalowners’ and Miners’ Associations, for the purpose of determining whether the fumes produced by certain explosives are injurious to health.  Both owners and workmen were represented on the committee, which elected Mr T. Bell, H.M.  Inspector of Mines, as its chairman, with Professor P.P.  Bedson and Drs Drummond and Hume as professional advisers.  The problem considered was whether the fumes produced by the combustion of certain explosives, one of which was roburite, were injurious to health.  The trial comprised the chemical analysis of the air at the “intake,” and of the vitiated air during the firing of the shots at the “return,” and also of the smoky air in the vicinity of the shot-holes.  Five pounds and a half of roburite were used in twenty-three shots.  It had been asserted that the fumes from this explosive contained carbon-monoxide, CO, but no trace of this gas could be discovered after the explosion.  On another occasion, however, when 4.7 lbs. of roburite were exploded in twenty-three shots, the air at the “return” showed traces of CO gas to the extent of .042 to .019 per cent.  The medical report which Drs Hume and Drummond presented to the committee shows that they investigated every case of suspected illness produced by exposure to fumes, and they could find no evidence of acute illness being caused.  They say, “No case of acute illness has, throughout the inquiry, been brought to our knowledge, and we are led to the conclusion that such cases have not occurred.”

Manufacture.—­As now made, roburite is a mixture of ammonium nitrate and chlorinated di-nitro-benzol.  The nitrate of ammonia is first dried and ground, and then heated in a closed steam-jacketed vessel to a temperature of 80 deg.  C., and the melted organic compound is added, and the whole stirred until an intimate mixture is obtained.  On cooling, the yellow powder is ready for use, and is stored in straight canisters or made up into cartridges.  Owing to the deliquescent nature of the nitrate of ammonia, the finished explosive must be kept out of contact with the air, and for this reason the cartridges are waterproofed by dipping them in melted wax.  Roburite is made in Germany, at Witten, Westphalia; and also at the English Company’s extensive works at Gathurst, near Wigan, which have been at work now for some eighteen years, having started in 1888.  These works are of considerable extent, covering 30 acres of ground, and are equal to an output of 10 tons a day.  A canal runs through the centre, separating the chemical from the explosive portions of the works, and the Lancashire and Yorkshire Railway runs up to the doors.  Besides sending large quantities of roburite itself abroad, the Company also export to the various colonies the two components, as manufactured in the chemical works, and which separately are quite non-explosive, and which, having arrived at their destination, can be easily mixed in the proper proportions.