352 Professor Bischof on the Origin of 
composition of the water circulating in the vein-cleft 
changed. 
Thus, Dr Speyer of Hanau, found, near Dietesheim, encasing 
pseudomorphous crystals of sparry iron, of the form of cale- 
spar.* They occurin the druses of Anamesite, in which, too, 
spherosiderite is not unfrequently met with. It is not to be 
doubted that waters, which at an earlier period had deposited 
cale-spar, as they changed their nature and became charged 
with acid carbonate of the protoxide of iron, have effected the 
exchange between cale-spar and sparry iron. . We do not re- 
quire to ask whether that portion of earbonic acid which changes 
the neutral carbonate into bicarbonate, has a greater affinity 
for carbonate of lime than for carbonate of the protoxide of iron, 
or inversely ; for there are many examples in chemistry of an 
inversion of affinities, under different circumstances, namely, 
when unequal masses operate. Water, charged with the bi- 
carbonate of the protoxide of iron, may, if it flows uninterrupt- 
edly over cale-spar, part with the half-combined carbonic acid 
to this latter, and so dissolve it and carry it off, and, on the 
other hand, deposit the carbonate of the protoxide of iron thus 
become insoluble. But just as well might the reverse case 
occur, and the half-combined carbonic acid in a water charged 
with acid carbonate of lime be given off to sparry iron, and 
so the former be deposited, and the latter dissolved. In the 
first case, the greater mass of the half-combined carbonic acid 
in the bicarbonate of iron is effective ; in the latter, on the 
other hand, that of the half-combined carbonic acid in the bi- 
carbonate of lime; for, in the one case, new portions of the 
iron compound, in the other new portions of the lime com- 
pound, are uninterruptedly brought to bear by the water in 
circulation. Besides, the poss¢bility of cale-spar occurring in 
the form of sparry iron cannot be doubted, although no such 
case is known. 
That these pseudomorphous crystals of sparry iron, in the 
form of cale-spar, are produced in the wet way, no one will 
doubt. The crystals of sparry iron are partly hollow in the 
interior, partly more or less filled with cale-spar; the inner 
* Die Pseudomorphosen des Mineralreichs, von Blum.—Stuttgart 
1843; S. 304. 
