On the Precipilation of the. Oxide of Gold hj Polash. 227 



land shells; admitting always, as every thing seems to p^ove, that 

 these shells are still in the place where they have lived originally. 



2. If we could suppose with some naturalists, contrary to all 

 appearance, that the strata called fresh-water strata have been 

 all formed under sea water, the present experiments will ac- 

 count for the absence (in other respects very remarkable) of the 

 bivalve river shells of the genera anodontes, mulettes, and cy- 

 clades. In fact, we have seen that the moUuscae which live in 

 these shells were not able to live in water charged like that of 

 our seas, with 0-04 of saline substances. 



3. Since it results from experiments many times repeated, that 

 the moUuscae, at least those of fresh water, cainiot live in water 

 charged with sulphate of lime, we can account for there being 

 no shells in the gypseous mass of Montmartre, and in general in 

 the old or new gvpsums, although they are frequently in layers 

 subordinate to shelly strata. 



4. Since the marine molluscse can live in water almost satu- 

 rated with muriate of soda, it would seem that the absence of 

 living organized bodies in lake Asphaltus, if this really be the 

 case, is owing to the presence of the bitter muriates of lime and 

 magnesia, and ))erhaps to that of the bituminous matters which 

 Lavoisier has not found in his analysis, without doubt, because 

 they are but occasionally met with and under certain circum- 

 stances onlv. 



On the other hand, since the sea mollusce perish in water 

 hvpersaturatcd with muriate of soda, it is not astonisiiing that 

 none of their remains have been found in the immense masses of 

 sal gemma, which are found in various countries. 



5. Lastlv, if \Ve admit that sea and fresh water moUuscae can 

 live in the same liquid, it would seem to result, that the fact of 

 living in fresh or in salt water cannot be a reason for establishing 

 particular genera, unless we can find sufficient and constant 

 characters in shells, or, what is better still, in the animals which 

 occupy them, when they are not fossil. 



XLVII. On the Precipitation of the Oxide of Gold hj Potash. 

 By M. FiGUiKR. Extracted hij AT. Gay-Lussac*. 



vJoLl), the propel tics of which have been so long too imper- 

 fcctlv known, and on which nuich yet remains to be done to place 

 its history on a level with that of most of the other metals, has been 

 recently dihgeutlv examined by M. Figuicr, an eminent chemist 

 of Montpelier. Messrs. Vau(iuelin, Duportal and Felleticr had 



* AnnaJts di Chimlr et Vhi/niqve, tomo ii. p. lOJ. 



P 2 asRerp«>d 



