74 Dr Bone's Observations on M. BeiidanCs Opinions 
Lastly, M. Bendant adduces as a proof in favour of the Nep- 
tunists, the comparison of the old porphyry masses, which ap- 
pear to lead to the igneous idea, with those porphyry masses 
which seem to sanction the Neptunian idea of their origin ; and 
he concludes, from the predominance of the latter, that the 
^ Neptunian probabilities are greater than the igneous ones. I 
am sorry to be obliged to say that this reasoning is altogether 
false, being founded on erroneous views ; in fact, M. Eeudant 
has not himself visited all the porphyritic countries which he 
looks upon as evidently of Neptunian origin, — he has only read 
their descriptions, or seen specimens of them. Had he examined 
them, he would have found that the Thuringerwald contained 
scoriaceous and porous porphyries in abundance ; that at Halle 
a great many igneous appearances are exhibited in the porphy- 
ries, which were unknown or neglected through a preconceived 
Neptunian hypothesis ; and, lastly, he would have been able to 
see the same phenomena in the Rhine countries, and even the 
Erzgebirge would have furnished him with most surprising ig- 
neous appearances 
I imagine I may now also conclude, in contradiction to M. 
Beudant, at least if I adopted the necessity of the principle 
which he expresses, by saying, that the porphyry masses lead- 
ing to igneous ideas being much more numerous than those 
which lead to tlie contrary opinion, the igneous probability is 
far greater than the Neptunian one.” 
Our author goes from the porphyries to the basaltic rocks ; 
lie perceives, on the one hand, a great analogy between the mo- 
dern basalts and those of the older red sandstones, of the grey- 
wacke, and , even of the mica-slates ; he sees every where the 
same prismatic structure, the same other particular forms, and 
the same augite : but, on the other hand, he soon observes that 
there is no olivine in ancient basalts, and that this mineral exists 
always in modern ones, when they are examined over a sufficient 
extent of country. (P. SOI.) 
In the first place, I most positively deny this last proposition, 
unless M. Beudant understands by a sufficient space the basalts 
of a whole group ; and, besides, how often are not cones and 
See my Memoir in the Journal etc Phjsiqxic, for 
