376 On some Relations of the Salts of Lime and Magnesia, 
59. The greater number of dolomites and magnesian rocks 
are shown by their fossils or by the nature of the associated 
strata to be of marine origin, but dolomites are also found m 
fresh-water deposits. Such is that with excess of magnesian 
carbonate from the brown-coal formation near Giessen (§ 57), 
and dolomites are said to occur with the lacustrine limestones of 
Dachingen near Ulm.—(Senft, Die Felsarten, 133.) 
Vv 
On the mode of formation of the preceding rocks. 
60. Having in the fourth division of this paper brought to- 
gether the principal facts in the history of magnesian rocks, as 
well from the researches of others as from our own observations, 
sla ees to the observations of Von Morlot and Marignac. 
’ [4], Vl, 
* Bischof cites Fournet, Histoire de la Dolomie, 1847, but I have not been able 
to consult the work in the ion of this paper. 
