gible on the supposition of tubes filled with foreign matters, but not on that of dendritic crystallization.

If all specimens of Eozoon were of the acervuline character, the comparisons of the chamber-casts with concretionary granules might have some plausibility. But it is to be observed that the laminated arrangement is the typical one; and the study of the larger specimens, cut under the direction of Sir W. E. Logan, shows that these laminated forms must have grown on certain strata-planes before the deposition of the overlying beds, and that the beds are, in part, composed of the broken fragments of similar laminated structures. Further, much of the apparently acervuline Eozoon rock is composed of such broken fragments, the interstices between which should not be confounded with the chambers; while the fact that the serpentine fills such interstices as well as the chambers shows that its arrangement is not concretionary.* Again, these chambers are filled in different specimens with serpentine, pyroxene, loganite, calcareous spar, chondrodite, or even with arenaceous limestone. It is also to be observed that the examination of a number of limestones, other than Canadian, by Messrs. King and Rowney, has obliged them to admit that the laminated forms in combination with the canal-system are "essentially Canadian," and that the only instances of structures clearly resembling the Canadian specimens are afforded by limestones Laurentian in age and in some of which (as, for instance, in those of Bavaria and Scandinavia) Carpenter and Gümbel have actually found the structure of Eozoon. The other serpentine-limestones examined (for example, that of Skye) are admitted to fail in essential points of structure; and the only serpentine believed to be of eruptive origin examined by them is confessedly destitute of all semblance of Eozoon. Similar results have been attained by the more careful researches of Prof. Gümbel, whose paper is well deserving of study by all who have any doubts on this subject.

In the above remarks I have not referred to the disputed case of the common limestones; but I may state that I have not been able to satisfy myself of the occurence of the structures of Eozoon in such specimens as I have had the opportunity to examine. It is perhaps necessary to add that there exists in Canada abundance of Laurentian limestone which shows no indication of the structures of Eozoon. In some cases it is evident that such structures have not been present. In other cases they may have been obliterated by processes of crystallization. As in the case of other fossils, it is only in certain beds, *I do not include here the "septariiform" structure referred to above, which is common in the Canadian serpentine and has no connection with the forms of the chambers.

+ Such Irish specimens of serpentine limestone as I have seen, appear much more highly crystalline than the beds in Canada which contain Eozoon.

and in certain parts of those beds, that well-characterized specimens can be found. I may also repeat here that in the original examination of Eozoon, in the spring of 1864, I was furnished by Sir W. E. Logan with specimens of all these limestones, and also with serpentine-limestones of Silurian age, and that, while all possible care was taken to compare these with the specimens of Eozoon, it was not thought necessary to publish notices of the crystalline and concretionary forms observed, many of which were very curious and might afford materials for other papers of the nature of that criticised in the above remarks.

[The examination of a large number of sections of a specimen of Eozoon recently placed in my hands by Sir William Logan, in which the canal system is extraordinarily well preserved, enables me to supply a most unexpected confirmation of Dr. Dawson's statements in regard to the occurrence of dendritic and other forms of this system, which cannot be accounted for by the intrusion of any foreign mineral; for many parts of the calcareous lamellæ in these sections, which, when viewed by ordinary transmitted light, appear quite homogeneous and structureless, are found, when the light is reduced by Collin's "graduating diaphragm," to exhibit a most beautiful development of various forms of canal-system (often resembling those of Dr. Dawson's Madoc specimen, which cross the cleavage-planes of the shellsubstance in every direction. Now these parts, when subjected to decalcification, show no trace of canal-system; so that it is obvious, both from their optical and from their chemical reactions, that the substance filling the canals must have been carbonate of lime, which has thus completely solidified the shell layer, having been deposited in the canals previously excavated in its interior, just as crystalline carbonate of lime fills up the reticular spaces of the skeleton of Echinodermata fossilized in a calcareous matrix. This fact affords conclusive evidence of organic structure, since no conceivable process of crystallization could give origin to dendritic extensions of carbonate of lime disposed on exactly the same crystalline system with the calcite which includes it, the two substances being mineralogically homogeneous, and only structurally distinguishable by the ef fect of their junction-surfaces on the course of faint rays of light transmitted through them.-W. B. C.]

[The preceding paper was drawn out in part by the observation of Messes. King and Rowney on the Eozoon published in the Quarterly Journal of the Geological Society, vol. xxii, pages 185 to 217, and illustrated by two plates. The following are the Summary and Conclusion with which the paper of Messrs. King and Rowney closes.-EDS.]

X. Summary. Although zealous advocates at one time for the organic origin of "eozoonal" Ophite, we now, after a prolonged investigation, and after, as we believe, leaving no point unnoticed, feel ourselves under the necessity of totally relinquishing that opinion.

It has been seen (1) that the "chamber-casts" or granules of serpentine are more or less simulated by chondrodite, coccolite, pargasite, &c., also by the bytryoidal configurations common in Permian Magnesian Limestone; (2) that the "intermediate skeleton" is closely represented, both in chemical composition and other conditions, by the matrix of the above and other minerals; (3) that the " proper wall" is structurally identical with the asbestiform layer which frequently invests the grains of chondrodite-that, instead of belonging to the skeleton, as must be the case on the eozoonal view, it is altogether independent of that part, and forms on the contrary, an integral portion of the serpentine constituting the "chamber-casts," under the allomorphic form of chrysotile-and that perfectly genuine specimens of it, completely simulating casts of separated nummuline tubules, occur in true fissures of the serpentine granules; (4) that the "canal-system " is analogous to the imbedded crystallizations of native silver and other similarly conditioned minerals, also to the coralloids imbedded in Permian Magnesian Limestone-that its typical Grenville form occurs as metaxite, a chemically identical mineral imbedded in saccharoidal calcite; (5) that the type examples of "casts of stolen-passages" are isolated crystals apparently of pyrosclerite. Furthermore, considering that there has been a complete failure to explain the characters of the so-called internal casts of the "pseudopodial tubules" and other "passages" on the hypothesis of ordinary mechanical or chemical infiltration, also bearing in mind the significant fact that the "intermediate skeleton," in Irish and other varieties of "eozoonal rocks," contains modified examples of the "definite shapes" more or less resembling the crystalline aggregations and prismatic lumps in primary saccharoidal marbles-that "eozoonal" structure is only found in metamorphic rocks belonging to widely separated geological systems, never in their unaltered sedimentary deposits,-taking all these points into consideration, also the arguments and other evidences contained in the present memoir, we feel the conclusion to be fully established, that every one of the specialities which have been diagnosed for "Eozoon Canadense" is solely and purely of crystalline origin: in short, we hold, without the least reservation, that, from every available standing point-foraminiferal, mineralogical, chemical, and geological-the opposite view has been shown to be utterly untenable.

XI. Conclusion.-From what has been stated in some of the preceding pages, respecting the various chemical changes which eozoonal" Ophite appears to have undergone, and its mineralogical constituents, we are strongly inclined to believe that it is a pseudomorphic rock, that it existed at one time in the ordinary metamorphic state, perhaps as hornblendic or augitic gneiss, and that it is primarily of sedimentary origin. Whether the same may be concluded of all ophitic rocks is a question on which we cannot offer any opinion-negative, or affirmative. There are some grounds for believing, however, that certain dolerites, generally considered to be of eruptive origin, have become changed into Ophite: and though we have not detected any "eozoonal" structure in an example apparently of the kind, from Monzoni in the Tyrol, which has fallen under our observation, it would not surprise us if this structure were found in ophitic rocks supposed to belong to the eruptive section, considering that the essential mineral (augite) of dolerite contains a large percentage of silicate of lime.

ART. XL.-Reply to Mr. Gabb on the Cretaceous rocks of California; by T. A. CONRAD.

In the last number of this Journal, Mr. Gabb in some remarks on the age of certain fossils of California, charges me with an "unfair avoidance of a difficulty." I am not aware of either a difficulty or unfairness. The latter refers to the omission of several of his species in my Eocene Check List. This I did for the sufficient reason that I could not be sure whether his typical form was from division A or B of his Cretaceous rocks. I believe that he has in only one instance figured a supposed identical species from each division, and in that instance the shells are not specifically, nor I think even generically related. After such experience, it could hardly be expected that I should trust his judgment in other comparisons.

Mr. Gabb includes the genus Anchura Conrad, in division B, but from his statement in his Paleontology it appears not to have been found associated with other fossils, and therefore it is much more likely to be a genus of division A, inasmuch as it has never been found in the Tertiary of any region. He says that the genera Gyrodes, Perrisolax and Margaritella are strictly Cretaceous, which I admit, but his species of Perrisolax in division B, is a member of an Eocene genus Levifusus, and which is closely related to a Claiborne species. He makes no mention of Gyrodes in division B, in his Paleontology, and of Margaritella he refers M. globosa to division A, and makes no

mention of its occurrence in division B, and M. crenulata he refers to no particular division.

It can hardly be reasonable to complain of my omission of Callianassa in a Check List devoted exclusively to Testacea, and I doubt the identification of such imperfect specimens of crab's hands as he has figured.

I omitted Ammonites n. s. because it was neither figured nor described, and might be an accidental intruder among Eocene fossils, as so many Cretaceous shells have been found to be. Would it be fair to place the Miocene beds of Cape Fear river, N. C., in the Cretaceous formation on account of the presence of two Cretaceous fossils, Exogyra costata and Cucullæa vulgaris?

Mr. Gabb compares his division B to the Maestricht beds, but the latter contain Belemnites, Ammonites, Baculites and Hamites, and according to Lyell, no Tertiary species; whereas Mr. Gabb includes in his division B, the Tertiary genera Aturia, Venericardia, Dosinia, Pseudoliva and Ficus. His Dosinia elevata, however, is a species of a very different Eocene genus, Dosiniopsis Conrad. D. pertenuis Gabb is either another species of Dosiniopsis or a younger specimen of elevata. D. gyrata is not stated to occur in division A, and D. inflata can hardly be a Dosinia. Any evidence so far is wanting to prove the strata in question Cretaceous, and as the group of fossils is so decidedly Tertiary in their forms and some species identical, I am forced to the conclusion of their Eocene origin.

ART. XLI.-Geographical Notices.

I. NOTE ON THE DIVERSITIES IN PUBLISHED ESTIMATES OF THE HEIGHT OF MOUNT WASHINGTON, NEW HAMPSHIRE.

THE variation, in statements pretending to approach accuracy, concerning the height of Mt. Washington, has been before remarked, but it may be interesting to see, in numerical order, the principal computations, and estimates given, in English feet, above the level of the sea. They are as follows:

1. 6,103, as quoted by Prof. Jacob Bigelow in an article presently to be mentioned, from the observations of Capt. Alden Partridge, of Norwich, Vt.

2. 6,128, given on the maps of Colton's General Atlas, edition of 1866; though in the text of the same work the height given is 6,496 feet, we are not told on what authority.

3. 6,225, from barometric observations, made in July, 1816, by a botanical party, comprising Prof. Jacob Bigelow, M. D., of

AM. JOUR. SCI.-SECOND SERIES, VOL. XLIV, No. 132.-Nov., 1867.