NATURAL PHILOSOPHY. 125 



Iron, wrought, • • • 487 



Limestone, hydraulic, 2.7 .. . 150 



" magnesian, 2.5 . . . 130 



Manganese, binoxide of, 4.8 . . . 294 



Malachite, 4.0 ... 248 



Mica, 2.8 ... 160 



Novaculite, or whetstone, 3.0 .. . 186 



Ochre, 3.5 ... 217 



Platinum, metal and ores, 16 to 19 . .1116 



Porcelain clay, 2.0 . . . 140 



Pyrites, iron, 4.5 .. . 280 



Quartz, pure, compact, 2.6 . . . 155 



" loose, angular, and round sand, .... — . . . 100 



Trap, 3.0 ... 186 



Vitreous copper, copper glance, 5.5 . . . 341 



Wood tin, stream tin, 7.0 . . . 434 



Zinc, sulphide or blende, 4.0 . . . 248 



Zincite, red zinc ore, 6.5 , . . 331 



Zino carbonate, 4.4 ... 268 



Zinc silicate, 3.4 ... 200 



ATOMIC MOTION. 



Prof. J. F. Walling, of Lafayette College, of Easton, Pa., read 

 a paper at the 1868 meeting of the American Association for the 

 Advancement of Science, on Atomic Motion. 



After making the general statement that all the physical phe- 

 nomena of the universe were made up of motions of matter. Prof. 

 Walling went on to unfold a new theory of force and the consti- 

 tution of matter based upon the fundamental idea of one grand 

 primary universal force. He deemed it necessary, in order to 

 avoid the difficulties and inconsistencies of existing hypotheses, to 

 commence with strict definitions of force and matter. These were 

 given as follows : Force is that which when associated with matter 

 causes motion. Matter is that which can be moved. Its sole proper- 

 ties, per se, are quantity (synonyms, weight, inertia) and position. 



The theory of Boscovich, a Russian philosopher of the last cen- 

 tury, supposed atoms to be alternately attracted and repelled at 

 minute distances, according as their distance varied. That of 

 Prof. Norton, of Yale, supposed material atoms to be surrounded 

 by atmospheres of one or more ethers, whose atoms repelled eacli 

 other but attracted those of matter. 



A new theory had been suggested by Sir William Thomson, of 

 Edinburgh, in which vortex atoms were supposed to constitute the 

 different kinds of matter. The kind of motion which he supposed 

 to take place is seen in the well-known smoke rings which we 

 sometimes see issuing from the muzzles of guns, the stacks of 

 locomotives, etc. 



This attempt of Thomson is based upon the mathematical dis- 

 covery of Helmholtz, that a vortex motion, or wirbelbewegung, 

 as he calls it, when once instituted in a jDerfect fluid, would con- 

 tinue forever. Such a theory is a step in the right direction, as it 

 removes one of the absurdities of the old theories, namely, that of 

 solid atoms. He then proceeded to show that, by his hypothesis, 

 11* 



