C. A. Goessmann on the Chemistry of Common Salt. 81 
changes now indicated. The agencies which produced these 
changes are still at work ; and hence the oceanic waters of the 
present day are liable to similar alteration in composition. There 
are reasons to suppose that for some time past one of the main 
changes has been the decomposition of the sulphate of lime by 
carbonate of magnesia, forming carbonate of lime, sulphate of 
and chlorid of magnesium. The latter compounds are 
characteristic of the salt deposits of recent date, as well as of 
the present marine waters; they could make their appearance 
only after the chlorid of calcium had been removed. There 
are of course various other means, by which this result may 
have been accomplished ; but I prefer to confine myself to the 
one now given, as being of particular interest in view of the 
fact, that chlorid of calcium is a characteristic constituent of the 
ante-tertiary ocean. These changes in the oceanic waters ex- 
tend apparently over long periods of time; they are more likely 
sib We do not hesitate on the strength of these observa- 
tions, to speak in general terms of a primitive ocean,—of an 
anie-tertiary or Silurian ocean, and of a Post-tertiary ocean, in- 
cluding in the latter that of the present day. 
Whenever during the various geological epochs a larger or a 
~chay renders the existence there of chlorid of calcium impos- 
smaller body of salt water was cut off from the main ocean, either 
in consequence of a receding of the ocean, | ior 
‘al basins, or of changes in the level of the strata, and was 
nan 
‘vaporation and the subsequent preservation either in whole 
or in part of its saline residue, then.a salt deposit was pro- 
Am. Jour. Sct. Snconp Serres, Vou. XLIX, No. 145.—Jan., 1870. 
6 
