688 THE POPULAR SCIENCE MONTHLY, 



and is not likely to afford any features of important interest. The 

 same is the case, in a higher degree, with the most of Arabia, which the 

 inhabitants themselves say God created in anger, and which the travels 

 of Palgrave and Blunt show is not likely to afford enough scientific 

 results to pay for the toil and dangers of a thorough examination. 

 Our knowledge of Mesopotamia and Syria is being rapidly increased by 

 the zeal of antiquarian explorers, whose investigations, although they 

 are rather historical than geographical, and concern the past rather 

 than the present, are not without results of contemporary interest. In 

 Asia Minor and Armenia, researches already carried on need to be 

 completed and systematized and made generally applicable to the whole 

 country ; and there are spots within three or four days' journey from 

 Constantinople that still need to be thoroughly worked out. 



We are back in Turkey, whence we started, but on the southern 

 instead of the northern side of the Hellespont and Bosporus. We 

 might complete our tour by examining these straits, and finding 

 whether they are traversed by a single current, carrying the waters of 

 the Black Sea into the Mediterranean, or by two currents, one super- 

 ficial and running to the west, the other submarine and directed tow- 

 ard the east a question that may have a bearing on the future of the 

 countries east of the Black Sea. Revue Scientijique. 



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WHAT IS A MOLECULE? 



MODERN science declares that every substance consists of an 

 aggregation of extremely small particles, which are called 

 molecules. Thus, if we conceive a droj) of water magnified to the 

 size of the earth, each molecule being magnified to the same extent, 

 it would exhibit a structure about as coarse-grained as shot ; and 

 these particles represent real masses of matter, which, however, are 

 incapable of further subdivision without decomposition. A lump of 

 sugar, crushed to the finest powder, retains its qualities ; dissolved 

 in water, the mass is divided into its molecules, which are still parti- 

 cles of sugar, though they are far too small to be seen by the highest 

 powers of the microscope. The physical subdivision of every body 

 is limited by the dimensions of its molecules ; but the chemist can 

 carry the process further. He " decomposes," or breaks up, these mole- 

 cules into " atoms " ; but the parts thus obtained have no longer the 

 qualities of the original substance. Hence the molecule may be con- 

 sidered as the smallest particle of a substance in which its qualities 

 inhere ; and every molecule, though physically indivisible, can be 

 broken up chemically into atoms, which are themselves the molecules 

 of other and elementary bodies. 



