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POPULAR SCIENCE REyiEW. 
coniine obtained from Coninm maculatum and Cicuta virosa. The boiling 
point is from 168° to 170° and also that of the native ; the specific gravity 
varies from 0*893 to 0 899 at 15°. The main difference, as regards the 
properties of the native and artificially-prepared coniine, is that the latter 
does not exbibit any optical rotatory action. See also “ Chemical News.” 
The Tungsten Compounds have been very thoroughly investigated by 
Professor Roscoe, F.R.S., who lately [February 15, 1872] read a paper on 
rhe subject before the Chemical Society. The paper is of some length, and 
should be consulted by those who are interested in the subject. 
GEOLOGY AND PALAEONTOLOGY. 
Crystals of Calcite surrounding Stalactitic Bitumen. — At a recent meeting 
of the Literary and Philosophical Society of Manchester [Feb. 6, 1872], 
Mr. Boyd Dawkins called attention to a remarkable group of crystals of 
calcite and sulphide of iron surrounding stalactitic bitumen, found at Castle- 
ton in Derbyshire, by Rooke Pennington, Esq. The mode of formation was 
this. When the mountain limestone of that district became charged with 
bitumen, the latter penetrated into a cavity which it traversed in long 
stalactite drops. Subsequently the cavity was more or less filled with 
crystals of calcite and sulphide of iron, which were deposited by the water 
charged with those substances around the drops of bitumen. The heat by 
which the bitumen found its way into the rocks must have disappeared 
before the crystals were formed j for had the latter been the result of 
hydrothermal action, they may have been coated, but certainly could not 
have been traversed by the solid bituminous stalactites. 
On the Value of Lithology in determining the Age of Rocks. — Clearly 
Professor Dana is not so much in favour of lithological evidence as Dr. 
Henry Hunt ; for, in a paper in Silliman’s u American Journal ” for Feb- 
ruary 1872, he says, in regard to Dr. Henry Hunt, that he has relied, for 
his chronological arrangement of the crystalline rocks of New England and 
elsewhere, largely on lithological evidence, and commends this style of evi- 
dence, when such evidence means nothing until tested by thorough stratigra- 
phical investigation. This evidence means something, or probably so, with 
respect to Laurentian rocks ; but it did not until the age of the rocks, in their 
relation to others, was first stratigraphically ascertained. It may turn out 
to be worth something as regards later rocks when the facts have been 
carefully tested by stratigraphy. A fossil is proved, by careful observation, 
to be restricted to the rocks of a certain period before it is used — and then 
cautiously — for identifying equivalent beds. Has anyone proved by careful 
observation that crystals of staurolite, cyanite, or andalusite, are restricted 
to rocks of a certain geological period ? Assumptions and opinions, how- 
ever strongly emphasised, are not proofs. It is no objection to strati- 
graphical evidence that it is difficult to obtain ; is very doubtful on account 
of the difficulties ; may take scores of years in New England to reach any 
safe conclusions. It must be obtained, whatever labour and care it costs, 
before the real order and relations of the rocks can be known. Until then, 
lithology may give us guesses, but nothing more substantial. 
