Fkbki'.\ky 8, 1895.] 



SCIENCE. 



157 



thonght-provokiug qualities; enigmatic, be- 

 cause no one has yet been able to say just 

 what Maxwell's views were The pursuit of 

 his treatise is like a journey through a 

 dreamland, wherein the travelers seem never 

 to reaeh their destinations. But the leading 

 idea is plain. It is that the medium is the 

 important factor, and on the medium the 

 attention must be riveted if we would seek 

 a satisfactory explanation of electricity and 

 magnetism. 



Faradaj- died twenty years before, and 

 Maxwell nine years before, anything like 

 crucial experiments decided in favor of their 

 theory. The old theories of action at a 

 distance, without the aid of an intervening 

 medium, but with their fluids and positive 

 and negative subtilties, died hard, if indeed 

 they can be said to be quite dead yet. The 

 recent investigations of Hertz and others, 

 however, seem to render it practicallj' 

 certain that the Faraday-Maxwell concep- 

 tion is the correct one, and that the medium 

 in question can be no other than the medium 

 of light and heat. 



Thus the multifarious phenomena of the 

 four sciences of heat, light, electricity, and 

 magnetism appear destined to become uni- 

 fied as the mechanical properties of a uni- 

 versal plenum. The present concentration 

 of activity along this line of inquiry seems 

 fraught with results of the greatest interest. 

 AVc seem to be, in fact, on the eve of <lis- 

 eoveries no less brilliant and important than 

 those whose record has already adorned the 

 history of mechanics. Nevertheless, it nuiy 

 not be our good fortune to witness such ad- 

 vances. The ether may prove intractable 

 for a eeuturj' or more. It is conceivable, at 

 any rate, that the full comprehension of this 

 medium lies beyond the present range even 

 of tliat extra sense which the late Charles 

 Darwin attributed to mathematicians. It 

 may be essential, in fact, to first give atten- 

 tion to visible and tangible substances, like 

 shoemaker's wax, before the mind will be 



prepared to visualize the hidden reality. 



But however this may be, mechanical sci- 

 ence will remain worthy of the arduous la- 

 bors of its devotees. The phenomena of 

 matter and motion, though suVyect to few 

 and simple laws, are infinitely varied and 

 infinitely instructive. The knowledge of 

 those phenomena already acquired gives as- 

 surance, as Helmholtz said in these halls a 

 year ago, that we possess the right method of 

 investigation. "\Ve may therefore expect 

 that a diligent application of this method 

 will yield in the future a not less inspiring 

 body of truth than that which has come 

 down to us from Archimedes and his suc- 

 cessors. E. S. Woodward. 



Columbia College. 



THE FIVE BOOKS OF HISTORY. 

 Ix the study of the phenomena of historj' 

 scientific men resort to five great classes of 

 records. The science of geology seeks to 

 discover the history of the earth — of the 

 rocks of which it is composed and of the 

 plants and animals wliich have lived from 

 time to time. In this research the geolo- 

 gist discovers that nature's last chapter eon- 

 tains a story of mankind, for it is found that 

 the bones of man and some of the works of 

 his arts have Ijeen buried by natural agen- 

 cies in the geologic formations. Sometimes 

 these materials of history are buried in 

 cave drift and in deposits derived from min- 

 eral waters which drop from the ceilings or 

 ooze from the crevices of the caves. In 

 flowing away and evaporating, such waters 

 leave behind certain mineral constituents, 

 especially carbonate of lime, which, consoli- 

 dating and crystallizing, accumulate over 

 the floors and walls of the caves and form 

 pavements of calcite and aragonite. From 

 the waters drojiping down from the ceilings 

 stalactites are fornu'd above and stalagmites 

 below, in marble cohunns of great natural 

 beauty. I'nder and within such formations 

 the bones of men and vestiges of their arts 



