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POPULAR SCIENCE MONTHLY. 



This was confirmed by finding traces of 

 zinc in a number of corpses. He 

 enumerates many ways by which zinc 

 was found to enter the soil, among 

 which are the following: The drainage 

 waters from many foundations con- 

 tain considerable quantities of zinc. 

 In all regions where zinc smelting is 

 carried on, or where there are zinc or 

 brass foundries, the vegetation contains 

 zinc; this arises from the fact that the 

 particles of zinc oxid are extremely 

 light and are carried to great distances 

 in the atmosphere. In one instance the 

 effluent from a slaughter house was 

 precipitated by an eflfective chemical 

 for the purpose which was sold under 

 the name of 'sulfate.' This precipitant 

 was found to be a very impure zinc 

 sulfate, containing much iron and 

 manganese. The excess of the substance 

 passed into the stream contaminating 

 it with zinc, while the precipitate, 

 consisting largely of zinc albuminate, 

 went with the other slaughter house 

 refuse as fertilizer. It is quite possible 

 that much of the 'tankage,' so largely 

 used in this country in the manufac- 

 ture of fertilizers, contains no incon- 

 siderable quantity of zinc. Where zinc 

 is thus present in the fertilizer, it 

 would be apt to pass in traces into the 

 fruit raised on soil thus fertilized. It 

 is reasonable to suppose that such 

 minute quantities of zinc would be per- 

 fectly harmless when taken into the 

 human system, but their detection 

 would serve to throw unjust discredit 

 upon American fruit growers, long 

 after they have ceased to use zinc in 

 any part of the evaporators with which 

 the fruit can come in contact; at least 

 when preparing dried fruit for the ex- 

 port trade, these precautions have for 

 some time been taken. 



AN ELECTROMAGNETIC BASIS 

 FOR MECHANICS. 



About forty years ago Maxwell 

 pointed out the main features of the 

 electromagnetic theory of light. This 

 theory very soon supplanted the old 



mechanical wave theory, or the elastic 

 solid theory; and now the fundamental 

 notions in light are purely electric or 

 electromagnetic in character. It is 

 very remarkable, however, that aside 

 from the change in the fundamental 

 notions themselves the old theoretical 

 structure remains to a very great ex- 

 tent unchanged and that even the old 

 nomenclature lends itself easily to the 

 needs of the new theory with few excep- 

 tions. The change that has followed 

 upon Maxwell's work is very like 

 the moving of a house from old to new 

 foundations. 



There is at the present time a pros- 

 pect of a similar transfer of the entire 

 subject of mechanics to a purely elec- 

 tromagnetic foundation. Every one re- 

 alizes that the notions of inertia and 

 of gravitation, and the principles in- 

 volved in Newton's laws of motion are 

 far too abstract in their nature, and as 

 elemental notions they are far too 

 complicated to be entirely satisfactory 

 as a basis for the most concrete of the 

 physical sciences. It seems that the 

 theory of electromagnetism is to sup- 

 ply precisely what is needful to reduce 

 mechanics to a more elemental basis. 

 The change, if it come, will no doubt be 

 similar to the change which has taken 

 place in the theory of light; the super- 

 structure of theoretical mechanics and 

 even the nomenclature will remain to 

 a great extent unaltered. 



The possibility of explaining the in- 

 ertia of matter electrically was first 

 shown by Heaviside. A charged body 

 has more momentum when moving at 

 a given velocity than if it were not 

 charged, and if the body is small 

 enough in comparison with its charge 

 all its momentum may be accounted 

 for in this way. 



The possibility of explaining gravi- 

 tation was first pointed out by H. A. 

 Lorentz, who attributes it to an excess 

 of attractive over repulsive forces of 

 electric charges. 



A remarkable consequence of Heavi- 

 side's theory of inertia is that accelera- 



