Page images
PDF
EPUB

The proportion of phosphate of lime is large, and may be owing to the impalpable remains of animals that must have frequented these early seas in myriads, or it may be peculiar to the little shelly remains of polythalamia that form such a large portion of this bed. The fluoride of calcium, which I believe is here pointed out for the first time as existing in marls, does not owe its origin to any spicule of bony matter present in the specimen examined, at least none that the microscope could detect; so we must attribute it either to osseous matter triturated to an impalpable powder, or, what is more probable, suppose that it forms a part of the calcareous covering of those animalculæ just alluded to, the remains of which form the foundation of the city of Charleston. The ammonia is held mechanically in the pores, associated perhaps with carbonic acid, and is easily rendered apparent by dropping caustic potash on the marl. This has been found present in all the marls I have examined, and the fluoride of calcium in several.

SOURCE OF FLUORINE IN FOSSIL BONES.

The analyses of fossil bones communicated by MM. Girardin and Preisser to the Academie des Sciences, October, 1842, afford the only well-detailed numerical results of the composition of this class of bones that we possess. The authors appear to have bestowed considerable care upon their research, and their estimate of the proportion of fluoride of calcium present was as follows:

Per cent.

A metacarpal bone of a bear from the cavern of Mialet... 1.09

Tusk of an elephant........

2.64

Vertebra of a plesiosaurus...

2.11

The great bone of the pækilopleuron bucklandii.

1.50

Rib of an ichthyosaurus....

1.02

Head of the same ichthyosaurus..

1.65

Bone of the lamentin from the tertiary formation in the
environs of Valognes .

9.12

This fluoride would appear to form a distinguishing mark between fossil and recent bones, although Berzelius has found it to exist in these latter, and Marchand, in some recent experiments, mentions the same fact; still many other chemists have not succeeded in detecting it. MM. Girardin and Priesser suppose that it was owing to some accidental circumstances that Berzelius was enabled to discover it in the cases that he examined, they having in no instance found it, although carefully sought for. My experience tends to confirm Berzelius in his statement, having in several cases obtained most decided evidence of its presence in recent bones, but in very minute quantity. In many instances I failed to detect it, and attribute the failure more to the minuteness of the quantity than to the total absence of it.

I would here remark that in examining for fluorine in the ordinary way, by testing the effects of the hydrofluoric acid (liberated by the action of sulphuric acid) upon waxed glass with characters traced out, the process requires some precaution when the quantity present is supposed to be very small;

for I have been able in several instances to obtain a permanent delineation of the characters traced without the presence of fluorine. In these cases it is caused by the action of the vapors of either sulphuric or hydrochloric acid upon certain kinds of glass that contain a large quantity of metallic oxides, or upon glass the surface of which has been altered by the action of the air. There is, however, no apparent corrosion in these cases.

The existence of fluorine in fossil bones, and its doubtful— or, as some say, absolute-non-existence in those of recent animals, have induced MM. Girardin and Preisser to conclude that it did not belong originally to the bones of fossil animals, but has found its way there by infiltration after their death; and they appear to have come to this conclusion without having examined the chemical character of the formations from which the various bones were taken.

I have had an opportunity of throwing some light upon this subject from the examination of two bones taken from the same calcareous deposit and within two feet of each other, the one cellular and the other compact. The cells of one of these bones were filled with small concretions of calcareous matter, evidently arising from the infiltration of some of the material forming the bed in which they lie. These concretions, it would seèm, ought certainly to contain a portion of whatsoever matter had been infiltrated, as all infiltrations must have passed in together. These concretions, carefully detached from the bone, were examined especially for fluorine, but not the slightest trace was found; while on the contrary a very small quantity of the compact part of the same bone gave decided indications of the presence of this substance. This fact must certainly lead to the conclusion that the fluoride of calcium in the body of the bone was not infiltrated; for had it been otherwise it would have been associated with matter known to be infiltrated, as the calcareous nodules.

The same cellular bone was examined as a whole-that is to say, without detaching the calcareous matter-in comparison with the compact bone from the same locality; and in the former there was found less fluoride of calcium than in the latter, contrary to what would have been the case had this fluoride been infiltrated.

[blocks in formation]

The deposit from which these bones were taken was analyzed, and fluoride of calcium detected, pertaining to mollusca or vertebrated animals; and were it necessary to suppose that it could have existed in only one of these, I should unhesitatingly attribute its origin to the vertebrated animals, particularly on account of their abundant provision of phosphates. Bones were also examined that contained fluorine when the deposit from which they were taken showed no traces of this element.

Dr. Daubeny has lately examined the question of the existence of fluorine in recent bones, and decided it in the affirmative.

It is not surprising that we should find the phosphates and fluorides associated in the animal kingdom; for in the mineral kingdom fluorine is a very common attendant upon the phosphates, as for instance in the apatites, wagnerite, wavellite, uranite, etc.; and I think if we search the mineral kingdom we shall not find so constant an association of any two elements as fluorine and phosphorus. All the phosphates of the alkalies and earths contain fluorine.

If then this element is associated with the phosphates, they must exist together in the soils arising from the disintegration of the rocks containing these minerals, and the plants growing upon these soils would upon taking up the phosphates naturally appropriate the accompanying fluorides, which two classes of salts would subsequently pass to the same portion of the animal feeding upon these plants—namely, to the bones.

The reason why the existence of fluorine in recent bones is doubtful may be owing to the fact that the great mass of the phosphate of lime originally in the soil has from various causes disappeared, and with it the fluoride of calcium; and that the portion of this latter still remaining is so small that notwithstanding the double condensation that it undergoes through the agency of plants and animals, it is not in sufficient quantity readily within the reach of our tests.

to come

CHROME AND MEERSCHAUM OF ASIA MINOR.

In my journey to the south of Broosa (Anatoly, Asia Minor) I crossed a formation of serpentine and other magnesian rocks of considerable extent. Fifty miles from this city I discovered chromate of iron disseminated in these rocks; and ten or fifteen miles farther south (near the city of Harmanjick) there is an abundant deposit of this mineral. A circumstance worthy of remark is that this chromate of iron (the first that has been discovered in Asia Minor) is found in serpentine as elsewhere. This important fact can explain to a certain extent the formation of this chromate. It is well known that serpentine contains all the elements of chromate of iron, which during the consolidation of this rock might separate themselves by the force of segregation, so well known to operate in many geological phenomena. Two facts which seem to confirm this supposition are; first, the existence of the chromate of iron in masses and not in veins; and secondly, the pale color of the serpentine associated with the chromate. One small specimen that I have consists of a white rock composed principally of carbonate of magensia, in which small specks of chromate of iron are visible. It is possible that this carbonate is the result of the decomposition of the serpentine at the surface by the action of water containing carbonic acid. It is only at this locality that I found crystals of the chromate octahedral, but very small.

This discovery is of great importance to the arts and to the Turkish Government, which proposes exploring the mine.

In quitting the locality of chrome and going north-east, I traversed in several places the serpentine containing veins of carbonate of magnesia, quite pure; and this occurs until we arrive at the plains of Eski-Shehr. It is from different parts of this plain that comes the meerschaum most esteemed in the arts. Its geological position is very different from what I had

« PreviousContinue »