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LETTER XXIII. 



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OPINIONS RESPECTING THE FORMATION OF COAL. ...EARTH IM- 

 PREGNATED WITH PETROLEUM, THE OPINION OF BUFFON 

 AND GENSANNE... .OPINION OF SIGN. ARDUINO....OF DR. BUT- 

 TON 'AND PROFESSOR PLAYFAIR....OF MR. WILLIAMS. ...OF 



MONS. TINGRY....OF DR. DARWIN. ...OF MR. KIRWAN....OF MR. 

 HATCHETT....OF MONS. PATRIN....OF MONS. FOURCROY. 



AMONG the humiliating proofs of our limited powers of inquiry, 

 there are few which are more striking, than that which is manifested 

 by the inefficiency of our investigations relative to coal. Respect- 

 ing the origin of this substance, so plentifully bestowed on us for 

 Our daily use, and consequently continually subjected to the im- 

 mediate examination of our senses, the most widely different opi- 

 nions have been held ; and by those, too, who have been the most 

 competent to form a proper judgment. Even with that theory 

 which has been the latest promulgated, by a gentleman whose ex- 

 traordinary knowledge in mineralogy and chemistry stamps a high 

 degree of authority on every opinion he adopts, I am under the 

 necessity of expressing my dissatisfaction. 



This circumstance is the more unpleasant, since the observations 

 which led to the objections to this ingenious theory, have also led 

 to the adoption of an hypothesis, which, although sufficiently seduc- 

 tive to hold my judgment captive, may be found, by the more 

 discerning, to posses much less probability than those opinions to 

 which it is opposed. To enable you to form a judgment on this 

 subject, I shall proceed to place before you those opinions which 

 have been most generally adopted, and such objections as seem to 

 affect their validity. 



VOL. I. H H 



