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249 
of the subject, in a scientific poiht of view, would not be without its 
weight." 
The connexion of magnetism with geology, is more intimate than it 
may appear to be to persons who have not informed themselves of the 
progress and present state of the sciences. In evidence thereof, it may 
be stated, that magnetic, and electro-magnetic powers, are active in dis- 
posing and arranging the materials composing the crust of the globe; 
their action, however, being more particularly proved in the transfer of 
metallic matter, or in other words, the operation of these forces furnish us 
with one mode of explaining how mineral veins have been filled. 
How much, or how influential these forces may be in the production 
of volcanic action, or whether they have had a distinct and perceptible 
influence in the general distribution of metallic matter, or how great 
their particular or general influence has been on the surface of the earth 
and in the depths beneath, we know not» 
Experiment and observation have not been sufficiently extended to 
enable us to answer these questions satisfactorily. We may be assured, 
however, of the fact, that changes are gradually effected by means of 
these and other agencies, which appear to co-operate with them, whose 
combined effects are not likely to be overrated. Heat, light, electricity, 
chemical affinity, capillary attraction, though often slow and silent in 
their action, yet they work a great amount of change in time. A stick 
of lunar caustic, if placed on a metallic plate, or in fact, if only ex- 
posed to the light, undergoes an entire change in the arrangement of its 
component parts — the silver re-appears in its pure metallic state — ^the 
antique bronze medals are converted into protoxide of copper — the feld- 
spar of a granitic column is perfectly decomposed by the laws of affinity, 
and by the operation of the same laws other bodies are re-produced, or 
re-composed, even in the tissues of organic bodies. Perfect crystals of 
calcareous spar, and of quartz, are developed from their solutions by 
electricity of feeble intensity, but acting for a lonsj time. What takes 
place on a small scale in a particular instance, is but an illustration of 
what may take place on a great scale in the interior of the earth. 
In an economical point of view, observations of this kind are not 
without their use. What we observe in Nature's own laboratory, may 
in many instances be imitated by us in oursj and if we cannot iinitaie, 
we may derive from her many useful hints. It is true, that Nature has 
at her disposal all time, and need not therefore be in haste to finish her 
work; she has, then, this advantage over us; yet this advantage is ma- 
[Assem. No. 200.J 28 
i 
