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the circumstances connected with their position, are such, that we are 
obliged to consider them as having been once in solution. Chemists 
are familiar with the fact that water under certain circumstances freely 
dissolves silex; besides, it is well known that it is held in solution in 
the hot springs of Iceland, St. MichaePs and many others in the vicinity 
of volcanoes; still, it is an insoluble substance after it has been once se- 
parated from water by precipitation, though in a state of minute subdi- 
vision. Again, silex becomes soluble by the assistance of the alkalies, 
potash and soda, especially when aided by heat. But the conditions 
under which it occurs in those beds are such, that no satisfactory ra- 
tionale offers itself in explanation of its solution. The following is the 
only one which occurs to my own mind, viz: that the silex is derived 
from the feldspar, and that by its union with the potash it becomes so- 
luble, either in the water of crystallization or of absorption, forming at 
one stage of its decomposition a silicate of potash; this compound, by 
subsequent reactions, suffers an entire separation of its elements, which 
finally results in the union of the particles of silex in the form of crys- 
tals or crystalline masses, and the entire removal of the potash by solu- 
tion. If this is the correct rationale, we are obliged still to maintain 
that only a part of the silex is employed in forming those nodules, for a 
portion still remains in mixture or combination with the alumine. The 
silex or quartz of the granite appears in coarse grains, diffused irregularly 
through the beds. 
Whatever rationale we may offer in explanation of this peculiar de- 
composition, we are furnished with a beautiful instance of a natural and 
spontaneous decomposition, or analysis of feldspar, as complete and per- 
fect as can be obtained in the laboratory of the chemist; so perfect in^ 
deed, that we are able to perceive each element side by side in each of 
those repositories, with the exception of the potash which is removed 
in consequence of its solubility in water. 
To assist our minds to comprehend more readily the law of those 
movements, which result in the formation of the concretionary masses, 
we may consider all the elements of the feldspar as forming at one time 
a plastic moveable mass like paste, and in which there is a perfect inter- 
mixture of the materials, or of the elements which composed the feld- 
spar originally. Under those circumstances, all the truly soluble parts 
would be washed away or removed by infiltration through the earthy 
materials. Those which remain would be left to be acted upon by mo- 
lecular attraction, and which would be exerted between particles of the 
same kind, or more especially between them. This influence would 
