PROGRESS IN EXPLOSIVES GUTTMANN. 287 



powder gun; the latter are made for modern weapons. The usual 

 " bulk " powders are composed of soluble nitrocotton mixed with 

 potassium or barium nitrate, and generally worked up in an in- 

 corporating mill or drum. The mixture is then either sprinkled with 

 water in a rotating drum, so as to form grains, or extended on a 

 shaking table making short and rapid oscillations. Alternatively it 

 may be put into an hydraulic press and then broken into grains, the 

 solvent being in every case sprinkled over when the grains are already 

 formed. 



The " condensed " powders are usually made by rolling the " paste " 

 into very thin sheets (0.1 millimeter and less), which are then cut 

 into small flakes to obtain the requisite rapidity of combustion. Such 

 powders are dried fairly quickly, and they may sometimes even be 

 boiled in water to promote elimination of the solvent. 



Since 1800, when Howard invented fulminate of mercury, and 

 since 1815, when Joseph Egg made the first cap, but little progress 

 has been made in the manufacture of these articles. It is still the 

 usual cap and the usual detonator, the only difference being that 

 potassium chlorate enters partly into the composition of detonators, 

 whilst for smokeless powders a hotter flame is found essential, and 

 is obtained by adding a combustible substance. Aluminum powder, 

 either mixed with the fulminate or pressed in a layer on top of it, 

 has been successfully employed.** The Rheinisch-Westfiilische Gesell- 

 schaft of Troisdorf make now detonators of tetranitromethylaniline 

 (called tetryl).'' It is said that quite half of all the detonators at 

 present manufactured in Germany are made with trinitrotoluene. 



The manufacture of fulminate of mercury is performed in almost 

 the same way as that described fifty years ago. 



The increasing demand for ammonium nitrate safety explosives 

 has resulted in the use of greater quantities of powerful detonators. 

 For the same reason great progress has been made with electric deto- 

 nators. Formerly high-tension fuses fired by frictional electric 

 machines were almost solely used, and Breguets were the only low- 

 tension fuses employed in mines. Nowadays the tendency is to use 

 low-tension fuses and magneto-firing apparatus, thus greatly reducing 

 the risk of firing the pit gases. 



BickfordV: invention still holds the field as regards safety fuses. 

 I have explained in my first lecture wherein the few improvements 

 consist that were made on safety fuses. It is curious that all attempts 

 to make a safety fuse with a core of smokeless powder or some other 

 nitro compound have so far been unsatisfactory. It seems impossi- 

 ble to insure uninterrupted burning. Of late, rapid-burning fuses 



o British patent No. 23366, of 1904. 

 6 Id. No. 13340, of 1905. 



