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Do we thoroughly understand the nature and pro- 

 perties of the atmosphere that surrounds us? That 

 immense congeries, not only of air and vapours, 

 whether of a watry or inflammable nature, but like- 

 wise of effluvia of every kind, which are continually 

 steaming out from solid as well as fluid bodies, in all 

 parts of the terraqueous globe ? Do all our instru- 

 ments, with all the improvements of them, suffice to 

 give us a thorough knowledge of its constituent 

 parts] Do they inform us of their innumerable 

 combinations and changes, with the remote and im- 

 mediate causes of them ? Very far from it ; and yet 

 it is not a barely curious know ledge, but useful in 

 the highest degree : seeing, for want of it, not only 

 various diseases, but often death itself ensues. 



Let us descend to what is of a still more firm and 

 stable nature, and subject to the scrutiny of all our 

 senses ; namely, the earth we tread upon, and which 

 God hath peculiarly given to the children of men. 

 Do the children of men understand this? Of what 

 parts then is it composed ? I speak now of its in- 

 ternal parts, in comparison of which, the surface is 

 next to nothing. Many arguments induce us to 



believe that the earth is between seven anil eipht 







thousand miles in diameter. How much of this do 

 we know 7 Perhaps some cavities, natural or arti- 

 ficial, which have been examined by men, descend 

 one, or even two miles, beneath its surface. But 

 what lies beneath these? Beneath the region of 



