32 COSMOS. 



tions which they follow over the long fissures with which 

 the earth's crust is furrowed. Relations of super-position of 

 trachyte and of syenitic porphyry, of diorite and of serpen- 

 tine, which remain doubtful when considered in the auriferous 

 soil of Hungary, in the rich platinum districts of the Oural, 

 and on the south-western declivity of the Siberian Altai, are 

 elucidated by the observations that have been made on the 

 plateaux of Mexico and Antioquia, and in the unhealthy ravines 

 of Choco. The most important facts on which the physical 

 history of the world has been based in modern times, have 

 not been accumulated by chance. It has at length been fully 

 acknowledged, and the conviction is characteristic of the agp, 

 that the narratives of distant travels, too long occupied in the 

 mere recital of hazardous adventures, can only be made a 

 source of instruction, where the traveller is acquainted with 

 the condition of the science he would enlarge, and is guided 

 by reason in his researches 



It is by this tendency to generalization, which is only 

 dangerous in its abuse, that a great portion of the physical 

 knowledge already acquired may be made the common pro- 

 perty of all classes of society ; but in order to render the 

 instruction imparted by these means commensurate with the 

 importance of the subject, it is desirable to deviate as \videly 

 as possible from the imperfect compilations designated, till the 

 close of the eighteenth century, by the inappropriate term of 

 popular knoivledge, I take pleasure in persuading myself that 

 scientific subjects may be treated of in language at once 

 dignified, grave and animated, and that those who are re- 

 stricted within the circumscribed limits of ordinary life, and 

 have long remained strangers to an intimate communion with 

 nature, ma}' thus have opened to them one of the richest 

 sources of enjoyment by which the mind is invigorated by the 

 acquisition of new ideas. Communion with nature awakens 

 within us perceptive faculties that had long lain dormant ; 

 and we thus comprehend at a single glance the influence 

 exercised by physical discoveries on the enlargement of the 

 sphere of intellect, and perceive how a judicious application 

 of mechanics, chemistry, and other sciences may be made 

 conducive to national prosperity. 



A more accurate knowledge of the connection of physical 

 phenomena ^ill also tend to remove the prevalent error that 



