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in basalt artificially fused and cooled slowly, and both in form 
and optical properties I found that they agree so closely with 
the small crystals of labradorite found in some natural 
igneous rocks, that I cannot see why, until facts prove the 
contrary, we should not consider them to be that mineral. 
Comparing then the artificial products with the natural 
rock we clearly perceive that there is no kind of similarity. 
The rock was fused and slowly cooled, but the resulting mass 
differs as much as it well could ; and, when it does to some 
extent resemble a natural rock, it is more like a basalt than a 
syenite or granite ; and in fact its structure is almost identical 
with that of some of the stony masses obtained by fusing 
basalt or basaltic lavas. I am, therefore, led to conclude that 
the conditions under which the natural rock was in a more or 
less fluid state and the artificial was melted were very 
different, as is especially shown by the quartz in the syenite 
containing so many fluid- cavities, holding portions of the 
water which was present when the rock was consolidated. 
This water, an intense pressure, and a far more gradual 
cooling, all of which we are unable to imitate successfully, 
probably suffice to explain the total difference in the structure 
of the natural and artificial products. At the same time, I 
must contend, that the making of such experiments, and the 
microscopical examination of the resulting masses, is likely 
to lead to a far better knowledge of igneous rocks than we at 
present possess. 
NOTICE OF AN APPARENTLY UNDESCRIBED FOSSIL PLANT, FROM 
THE CARBONIFEROUS SANDSTONE, NEAR LEEDS. BY MR. 
HENRY DENNY, A.L.S. 
The palaeontologist, whose labours are confined to the 
vegetable kingdom, has far greater difficulties to encounter, 
and far less satisfaction as to the accuracy of his conclusions, 
