SCIENTIFIC SUMMARY. 
257 
hydrochloric acid gas, agates and jaspers, coloured green and yellow, 
were converted into brownish stones. The action of dry hydrochloric 
acid is to convert the calcareous veins which traverse minerals, into 
chloride of calcium ; which, being soluble in water, we are thus enabled to 
make, as it were, an anatomical examination of certain compound mine- 
rals, and in this way to simplify their formulae. Hydrogen , by reducing 
the oxide of iron in certain red marbles and agates, causes these latter to 
assume a blackish colour. It reduces malachite to the metal state, and 
blackens lapis-lazuli. Ammonia gives red granite a blackish colour, the 
same as bloodstone. It reduces malachite, as above, and converts pyro- 
lucite into protoxide of manganese, with the production of nitric acid, the 
protoxide still preserving the crystalline form of pyrolucite. Cyanogen : 
this gas acts as an energetic de-oxydiser ; it removes the colour of 
amethyst, and yellow and red cornelian, leaving a deposit of carbon in the 
fissures of these stones. It also blackens red agates by reducing the oxide 
of iron. Hydro-sulphuric acid does not affect the smoked or yellow 
diamond, nor the sapphire. It gives the ruby a violet tint. Red quartz 
and amethyst are discoloured by it. Red cornelian is discoloured and 
loses its transparency on account of the formation of hydrates ; the tur- 
quoise is blackened, and marbles, granites, and agates, whose colour is due 
to oxide of iron, are similarly affected. M. Kuhlmann obtained the fore- 
going results by enclosing portions of the minerals in a porcelain tube, 
heating this to a temperature which, though elevated, was not sufficient to 
produce decomposition of the minerals, and then causing a stream of the 
gas in question to play upon the latter. — Yide L’lnstitut , November 
11 , 1863 . 
GEOLOGY AND PALAEONTOLOGY. 
Air Breathers of the Coal Period in Nova Scotia. — In a late number of 
the “ Canadian Naturalist and Geologist” we find a very valuable paper 
with the above title. It is from the pen of J. W. Dawson, F.R.S., a man 
well known for his many additions to the science of Geology : he describes 
four species of Hylonomus, one of Hylerpeton, two of Dendrerpeton, one 
of Baphetes, and one of Eosaurus, all of which belong to the class reptilia ; 
and he also describes two invertebrata, one a mollusk, Pupa vetusta ) and 
the other a centipede, Xylobius Sigillance. The coal measures of Nova 
Scotia like those elsewhere, present ample evidence of brackish and fresh- 
water conditions. But in this respect they are not exceptional. “ It is 
true that, in Great Britain, evidences of marine life do occur in the coal 
measures ; but not, so far as I am aware, in circumstances which justify 
the inference that coal is of marine origin.” The writer mentions that at 
Fort Lawrence we meet with a forest, growing in upland soil, forty feet 
below high-water mark and covered with mud, containing living Myas 
and Tellinas i but we are not justfied in supposing that this forest grew in 
the sea. Dr. Dawson is not content with mere descriptions of the air- 
breathers, but endeavours to strike a blow at the advocates of the doctrine 
of “origin of species by natural selection.” For example, he supposes 
