EXl»EiaMENTS ON IrfOLYfiDENA. £53 



spi'eacl tills sand, upon Which a fresh calc'areous deposition 

 took place ; and these operations could have occurred only 

 in the sea. Count Marzari has had the goodness to present 

 me a specimen of this sand, which is similar to what was 

 thrown out of the sviperior aperture of Etna in the eruption 

 of 1763, which I have mentioned above, 



I shall remind the reader here of what I have said seve- Distinction be- 

 I'al times, that to distinguish the different periods when anj^'extincr' 

 volcanoes have been burning, and uot to confound them volcanoes. 

 together, it is proper, to call those ancient, which have 

 burned in the sea before our continents were laid dry ; and 

 those only extinct, which by their situation are still capable 

 of burning, if the inflammable matters that gaA^e rise to 

 them were not consumed. But this necessary distinction 

 will never be made, as long as it is believed, in spite of 

 the dictates of observation and experience, that burning 

 volcanoes may exist independent of the waters of the 

 sea. 



Mr. 'Fl. de Bellevue must be convinced, tliat my sole jj^^ author'* 

 object, in making these observatior.s, is to illustrate in a object. 

 more precise manner the grand phenomenon of volcanoes, 

 that we may not ascribe to them effects in which they have 

 no concern, or deny them those they have really produced. 

 These limits, grounded on well established facts, can alone 

 free us from systems founded on contrary notions, and af- 

 ford more certain bases to geology, that interesting and im- 

 pwtant branch of terrestrial physics. 



II. 



Experiments on MolyhcUna. By Christiajj Frederic 



BUCHOLZ. 



(Cwicluded from p. \QQ.J 



VIII. Manner in which molybdena comports itself with cer' 

 tain acids. 



Exp. 29. JL EN" grains of powdered molybdena were put With sulphu. 

 into half a drachm of sulphuric acid of the specific gravity "'^ ^^'*^' 



of 



