THE SIZE OF MOLECULES. METEOROLOGY. 67 



presence of simple objects is concerned, bodies of even 

 smaller dimensions can be perceived. 



According to the views of Helmholtz, the smallest 

 particle that could be distinctly defined, when associated 

 with others, is about -g-o^^ n f an inch. Sorby esti- 

 mates that a particle of albumen of this size contains 

 125,000,000 of molecules. In the case of such a simple 

 compound as water the number would be no less than 

 8,000,000,000. Even, then, if we could construct 

 microscopes far more powerful than any we now possess, 

 they would not enable us to obtain by direct vision any 

 idea of the ultimate molecules of matter. Sorby calcu- 

 lates that the smallest sphere of organic matter which 

 could be clearly defined with our most powerful micro- 

 scopes would contain many millions of molecules of 

 albumen and water, and it follows that there may be an 

 almost infinite number of structural characters in 

 organic tissues, which we can at present foresee no 

 mode of examining. 



The science of Meteorology has made great pro- 

 gress ; the weather, which was formerly treated as a 

 local phenomenon, being now shown to form part of a 

 vast system of mutually dependent cyclonic and anti- 

 cyclonic movements. The storm-signals issued at our 

 ports are very valuable to sailors, while the small 

 weather-maps, for which we are mainly indebted to 

 Francis Gralton, and the forecasts, which anyone can 

 obtain on application either personally or by telegraph at 

 the Meteorological Office, are also of increasing utility. 



Electricity in the year 1831 may be considered to 

 have just been ripe for its adaptation to practical pur- 



o 



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