MISCELLANY. 



651 



vapor, viz., oxygen and hydrogen, are disso- 

 ciated at 1,298 Fahr. "If, therefore," says 

 the author, " we heat a bar of iron to fully 

 1,298, and place it over a globule of water 

 upon an anvil, a blow with a hamruer will 

 elicit the detonation of a rifle ; I have re- 

 peated this experiment often. The elements 

 of the water dissociate by the heat, and in- 

 stantaneously recombine in cooling, causing 

 the detonation." 



The degree of dissociation, as of evapo- 

 ration, depends on the pressure : under four 

 atmospheres (60 lbs.), the heat required for 

 dissociation is l^YO . But the question 

 arises, If the vapor dissociates at these 

 temperatures, why do not the gases instan- 

 taneously combine and detonate ? The rea- 

 son is plain : in the boiler the atoms at 

 once become mixed with a volume of steam 

 sufficient to render them inexplosive. 



The condition requisite for the genera- 

 tion of explosive gas in a boiler is that 

 vapor be in contact with a surface heated 

 to 1,298, or higher, according to the press- 

 ure, as we have seen. Now, this condition 

 may occur in a boiler filled with water, 

 owing to the property which that liquid 

 possesses of assuming the spheroidal 

 shape when in contact with a highly-heated 

 surface. "It is, therefore, not difficult to 

 conclude," says the author, " that, in case 

 of very heavy firing, a thin film of vapor 

 may form between the water and the boiler, 

 and, when this is once formed, the heating 

 of the boiler would be so rapid that noth- 

 ing but the cooling process of dissociation, 

 which would then commence, could save it 

 from completely burning through." 



Explosion would then occur whenever 

 1. The oxyhydrogen gas, as compared with 

 the steam, rises to the explosive proportion ; 

 or, 2. When the steam, by condensation, 

 falls to the explosive proportion. To make 

 explosion possible, the proportion of oxy- 

 hydrogen gas to vapor must be at least as 

 1 to 7. 



Scientific Education in England. Sir 



Josiah Mason, a manufacturer of Birming- 

 ham, is about to found a scientific college 

 in that town on a most liberal scale. It is 

 intended to afford thorough systematic 

 scientific instruction, specially adapted to 

 the practical, mechanical, and artistic re- 



quirements of that great centre of manu- 

 facturing industry. Systematic instruction 

 is to be given in mathematics ; abstract 

 and applied physics ; chemistry, theoretical, 

 practical, and applied ; the natural sciences,- 

 especially geology and mineralogy, with 

 their application to mines and metallurgy ; 

 botany and zoology, with special applica- 

 tion to manufactures ; and physiology, with 

 special reference to the laws of health. The 

 English, French, and German languages will 

 be taught, but mere literary instruction is 

 excluded. No principal, professor, teacher, 

 or other officer of the college, is ever to be 

 called upon to make any "declaration as 

 to, or submit to any test whatever of, his 

 religious opinions," and the institution is to 

 admit all persons " without distinction of 

 age, class, creed, race, or sex," to the popu- 

 lar lectures ; while the regular course will 

 be open to qualified persons of all classes, 

 "especially the more intelligent youth of 

 the middle class." This Nature calls " one 

 of the most princely gifts yet made to pos- 

 terity in England by one of her wealthy 

 sons." 



The Hotchkiss Revolver-Cannon. Some 

 trials were recently made, says the Revue 

 d'Artillerie, at the Satory Polygon, with a re- 

 volving cannon, invented by Mr. Hotchkiss, 

 and intended for the Italian Government. 

 The special object of these experiments was 

 to ascertain the mechanical value of this 

 engine. This new arm (whose calibre is 

 1+ inch) differs essentially from all other 

 mitrailleuses hitherto brought before the 

 public, particularly in this, that it dis- 

 charges a small cast-iron shell with percus- 

 sion fuse, the effects of which may be for- 

 midable at distances relatively considerable. 



We will, at another time, present a com- 

 plete description of this gun, but for the 

 present must content ourselves with giving 

 some details of the ammunition employed. 

 This consists of a cartridge with shell at- 

 tached. The cartridge proper consists of a 

 soldered tube of tin, with one end closed to 

 form a cup. This closed end is reenforced, 

 within and without, by two iron caps, and 

 fastened with three rivets to a broader iron 

 plate, which forms the true base of the 

 cartridge, bears the pressure of the gases, 

 and affords a grip to the extractor. The 



