506 



THE POPULAR SCIENCE MONTHLY 



and solidification at existing mean atmos- 

 pheric temperature, of basic and acid slags 

 analogous to melted rocks. Mallet thus 

 rinds that less than one-fourth of the heat 

 annually lost by our globe is sufficient to 

 account for its total annual vulcanicity. 

 lie then shows the accordance of his views 

 with sundry facts of vulcanology and seis- 

 mology. Finally, he accounts, on his the- 

 ory, for the elevations on our moon's sur- 

 face, and the evidence there of former 



1 m 



volcanic energy, on a grander scale than 

 on our planet. 



'i ho Vibrations produced by Various Ex- 

 plosives. It is known that the instanta- 

 neous combustion of an explosive body is 

 brought about by vibrations, independently 

 of the agency of heat. An interesting in- 

 quiry here arises, whether these vibrations 

 are identical for all explosives ; and whether 

 we can determine in advance the action of 

 one explosive upon another. Two French 

 savants, MM. Champion and Pellet, have in- 

 vestigated this subject, and the following 

 is an account of their experiments : First, 

 they set up an apparatus with eight gas- 

 burners, to give " singing " flames, answer- 

 ing to the eight notes of the gamut. For 

 the first experiment an anvil was placed at 

 a distance of sixteen feet from this appara- 

 tus, and on it they placed in succession 0.03 

 grammes of iodide of nitrogen and fulminate 

 of mercury, both enclosed in sacks of gold- 

 beater's skin. The iodide, on being ex- 

 ploded, had no effect on the flames, while 

 the fulminate caused the following flames to 

 play : la, do, mi, fa, and sol. The conclu- 

 sion is, that the vibrations produced by the 

 two agents differ mutually, and further, 

 that the vibrations caused by the fulminate 

 act on some notes, passing over the others. 

 In the second experiment the flame-appara- 

 tus and the anvil were placed twelve feet 

 apart. It was now found that the iodide 

 acted on the higher notes, whereas the ful- 

 minate affected the entire scale. But. if 

 now we make each charge two decigrammes, 

 and bring the anvil very close to the appa- 

 ratus, the whole gamut will respond to both 

 explosions. The third experiment was a 

 repetition of the foregoing two, with this 

 exception, that nitro-glycerine was substi- 

 tuted for iodide of nitrogen. The result did 



not show any difference between these two 

 agents in their action on the flames ; and 

 yet it is known that there is a difference be- 

 tween their respective vibrations; for the 

 fulminate will explode compressed gun-cot- 

 ton, but nitro-glycerine will not, under iden- 

 tical conlditions. No doubt, if a more per- 

 fect flame-apparatus, with a series of low 

 notes, had been employed, a difference 

 would have been manifested in the course 

 of the experiment. 



Economy of Fuel. A self-feeding fur- 

 nace is now in use in several English manu- 

 facturing towns, which is said to effect a 

 great economy in the consumption of coal, 

 besides possessing the additional advantages 

 of burning all the refuse and completely con- 

 suming the smoke. A small and uniform 

 amount of fuel, just enough to replace that 

 consumed, is being constantly added to the 

 fire, which is supplied with exactly as much 

 air as is required to carry on the combus- 

 tion in the most economical and effective 

 manner. The apparatus is known as Vicar's 

 Furnace, and is readily fitted to any kind 

 of boiler, and to reverberatory furnaces of 

 all descriptions. 



Ammonia in Snow-water. Dr. Vogel has 

 an article on ammonia in snow-water in the 

 Sitzungsberivhte der mathematico-pliysiJcali- 

 schen Classe, of the Munich Academy of 

 Sciences. The method employed by him 

 is that of Schlbsing, for estimating the 

 amount of ammonia in arable soil. The 

 results obtained were as follows, one litre 

 (2.113 pints) being the unit: Freshly fallen 

 snow, caught in a porcelain basin, at zero, 

 gave 0.003 grammes ; at 3 gave 0.002 ; 

 at from 9 to 15 gave no ammonia. 

 Water from snow which had stood 24 hours 

 on a piece of manured garden-ground, con- 

 tained 0.012 grammes; from snow which 

 had stood on a meadow for 24 hours, 0.009 

 grammes ; from a zinc roof, 0.004 grammes. 

 Dr. Vogel observes that the quantity of 

 ammonia in snow depends on a variety ol 

 conditions, and that, since snow, owing to 

 its porosity, absorbs ammonia (and the same 

 is true of snow-water), it is necessary to 

 melt it in closed vessels. The amount of 

 ammonia in snow is also dependent on the 

 temperature at which it falls. At a rather 



