60 | _ SCIENCE. 
idiom. Another objection is, that the practice intro- 
duces a distinction difficult to maintain on account of 
the graduation of the nominal into the adjective sense. 
‘The Carboniferous’ may or may not imply some 
such noun as formation, and the degree of such impli- 
cation is variable. 
Authors of the second group speak of the Potsdam 
and Potsdam strata, but of the carboniferous and 
carboniferous strata. The distinction thus made is 
etymologic, being based on the immediate derivation 
of the name of the formation. To this there are two 
objections. First, it is contrary to the analogies of 
the language, for capitalization is generally controlled 
by meaning. We speak of ‘the Pacific,’ although 
the designation is etymologically acommon noun; and 
we call the recently popular feminine waist-gear a 
jersey, although the designation is etymologically a 
proper noun. Second, it has the effect of recalling 
attention continually to the derivation of names, and 
thus retaining their connotative meaning. For mne- 
monic reasons, and for these only, it is convenient 
that names of formations should originally be conno- 
tative, but it is of prime importance that they should 
eventually become merely denotative. There was a 
certain original utility in having ‘ Potsdam’ eall to 
mind a place, and ‘ carboniferous’ a character; but 
the names having become securely attached to their 
several formations, it is now imperatively demanded 
that each shall designate a certain portion of the strat- 
igraphic column and a certain portion of geologic time, 
without connotating place or composition. Indeed, 
the reason why modern usage .employs geographic 
terms in the naming of new formations, instead of 
designating.them by their physical characters, is that 
a minimum of connotation is thus secured from the 
outset. 
Authors of the third class capitalize all names of 
formations, whether used as nouns or adjectives, and 
in so doing escape these evils. The only objection I 
see to their practice is, that it classes with proper 
nouns a group of names which may fairly be compared 
with other groups not so classed. The demarcation 
between common and proper nouns is essentially 
somewhat obscure; and the drawing of the line is 
largely a matter of practical convenience. It is note- 
worthy that no author whatever has so drawn it as 
to include all names of formations with common 
nouns. 
The capitalization of all formation names has the 
manifest advantage that it enables one to say that the 
Carboniferous rocks are not the only carboniferous 
rocks, or, in other words, that it doves not deprive the 
geologist of the independent use of words indicative. 
of rock cbaracter which have been appropriated for 
the names of formations. If the use of capitals were 
altogether discarded in the designation of formations, 
this advantage would be lost, but another would be 
gained; for we should then be able to speak of the 
rocks of Potsdam without implying their potsdam 
age. G..K. GILBERT. 
Remsen’s ‘ Theoretical chemistry.’ 
Will you kindly allow me to correct an error into 
which it seems that I fell, in my notice of Professor 
Remsen’s ‘ Theoretical chemistry’ (Science, ii. 826) ? 
It cannot be denied that the statement, ‘‘ Of the sub- 
stitution products of benzene which contain three 
substituting groups, more than three varieties have 
been observed,’’ is literally true. 
form of expression were such that I could not but 
think this assertion was made of those derivatives in 
which the three substituting groups were alike. Had 
it occurred to me that the statement was not thus lim- 
The cqntext and: 
Synchronism of geological formations. 
I trust that you will permit me a little more space — 
to reply to the further remarks of Mr. Nugent on this 
subject (Science, iii. 33), seeing that your correspond- 
ent has failed to grasp the point which I had in- 
tended to elucidate in my last communication. 
Mr. Nugent is correct when he contends that I rest’ 
my case on the non-occurrence of ‘ evidences of in- 
versions;’ and, if my line of argument based on this 
fact fails to meet with his approval, I sincerely regret 
it. Paleontology, as far as Iam aware, has thus far 
failed to show a single unequivocal case of faunal 
inversion such as I have indicated; nor does there ap- 
pear at the present time very much likelihood of its 
ever being able to do so. Nor would the discovery 
of a solitary instance materially affect the question, 
inasmuch as, upon the theory of very broad contem- 
poraneity suggested by Huxley, instances of inversion 
ought to be about as numerous as those of non-inver- 
sion. My courteous critic admits that ‘‘ there is no 
reason why such instances of inversion should not 
have occurred over and over again,”’ and that at the 
present time their ‘ occurrence is almost unknown;’ 
but his appeal to the ‘imperfection of the geological 
record’ (both geological and geographical), in expla- 
nation of the overwhelming negative testimony, will, 
I am afraid, scareely meet the situation. 
The special cases referred to — Barrande’s colonies, 
and the intermixture of Silurian and Devonian, and 
Devonian and carboniferous fossils in the old red 
sandstone of Scotland —are far from being of the 
character desired. The former need scarcely to be 
commented upon, since they have always been in- 
volved in a certain amount of obscurity; and their 
very existence as such has very recently been denied 
by Marr, who personally examined the region, Lap- 
worth, and a host of other geologists. In the case of 
the old red sandstone of Arran, where there is an in- 
tercalation of a band of marine limestone containing 
Productus giganteus, P. semireticulatus, P. puncta- 
tus, Chonetes hardrensis, Spirifera lineata, and other 
well-known carboniferous fossils, Professor Geikie 
(who, we believe, first made the observation) distinctly 
affirms that these organisms must ‘‘ have been in ex- 
istence long before the formation of the thick Arran 
limestone,”’ and that their habitat during the period 
of the deposition of the underlying sandstone was im- 
mediately outside of the basin or basins that through 
upheaval were now being gradually isolated from the 
sea: in other words, we have here merely an instance 
where the range of a certain number of organic forms 
has been extended somewhat lower down in the geo- 
logical scale than it had hitherto been indicated. 
These same forms re-appear in the superimposed lower 
carboniferous limestones, and, as Professor Geikie 
observes, they must have been living during the long 
interval coincident with the sedimentation of the 
intervening sandstone ‘ outside of the upper old red 
sandstone area.’ The same relation holds with the 
Siluro-Devonian mixture in the basal old red of Lan- 
arkshire. Noonecan deny the local displacement and 
interchange of portions of two consecutive faunas, 
especially at about the beginning or close of their own — 
respective series; but these displacements are not of 
the nature of the inversions that ought to illustrate 
the doctrine of broad contemporaneity. 
To what extent similar or identical faunas indicate — 
absolute chronological relationship can probably never 
ited, I certainly should not have pronounced it rash, 
but so cautious and incomplete that it must inevita- 
bly mislead even the most careful reader. } 
THE CRITIC. 
