68 Hints^or the Formation of 



drop or thin coating of nitrous acid j and beyond all expec- 

 tation, when you take a filver bow having a little fulphure of 

 pot-afli adhering to the end of it. 



Fig. 19 reprefents the form of this experiment, where g- 

 is the frog, a, a the two glaffes with water, A the bow formed 

 of one fingle metal, and m the drop or a thin ftratum of a 

 mucous, faline. Sec. fluid with which the bow has been rub- 

 bed over, and which on this fide is between the metal and 

 the water. 



[To be contiDiied.] 



*■ 



X. Agenda, or a Colle^ion of Ohfervat'tons end Refearches^ 

 the Refults of which may ferve as the Foundation for 

 Theory of the Earth. By M, DE Sa us SURE*, 



[Continued from page 299 of Vol. Ill,} 

 CHAF» XV. 



Obfervations to be made on primitive Mountains, 



x.W. 



HETHER there be aay exception to the gene- 

 rally received opinion, that, in primitive mountains, no 

 veftiges are difcovered of organifed bodies. 



3. Whether it be true that m thefe mountains no indica-, 

 tions are found of bitumen or marine fait. 



3. To endeavour to determine the refpeftive ages of the 

 different kincls of primitive mountains; both compound, 

 fuch as granite, porphyry, gneifs; and fimple, as Hate, fer- 

 pentine, and primitive calcareous. 



4. Whether, in particular, it be certain that granite is tlie 

 moft ancieat ftone of alt thofe which form the outer cruft of 

 our globe, fo that it is never &mid placed above {fuperpofi ) 

 amy other kind of ftoae. 



* From Joi'm«I Hcs Mines, N«. XX. 



5, Whether 



