traction, and by greater care employed in the collection of the boracic vapour. In 1833, about 650,000 Tuscan pounds were obtained; in 1836, two millions and a half.

But it appears to me that the powers and riches of these extraordinary districts remain yet to be fully developed. They exhibit a great number of mighty steam-engines, furnished by nature at no cost, and applicable to the production of an infinite variety of objects. In the progress of time, this vast machinery of heat and force will probably become the moving central point of extensive manufacturing establishments. The steam, which has been so ingeniously applied to the concentration and evaporation of the boracic acid, will probably hereafter, instead of wasting itself in the air, be,employed to move huge engines, which will be directed to the infinite variety of production which engages the attention of labouring and intelligent artisans; and thus, in the course of time, there can be little doubt, that these lagoons, which were fled from as objects of danger and terror by uninstructed man, will gather round them a large and intelligent population, and become sources of prosperity to innumerable individuals through countless generations.

On the Supposed Existence of Fluoric Acid, as an Ingredient in certain Animal Matters. By G. O. REES, M. D., F. G. S. &c.*

In the year 1802, Morichini published a paper, in which he declared fluoride of calcium to be an ingredient in human teeth. He was led to examine that substance from having succeeded in detecting the fluoride in a specimen of fossil ivory. Mons. Gay Lussac repeated these experiments; and in the 55th volume of the "Annales de Chimie," he states, that the fluoride exists in recent as well as in fossil ivory; and that he had also succeeded in detecting it in the tusks of the wild boar. Fourcroy and Vauquelin subsequently published a memoir in the 57th volume of the "Annales de Chimie," in which they positively denied the existence of fluoride of

* From Guy's Hospital Reports, No. ix. October 1839, pp. 381, &c.

calcium as an ingredient either in recent ivory or the enamel of teeth; they found it, however, in the fossil ivory of Argenteuil and Lourque, though it did not appear to exist in specimens from Siberia and Lay.

Baron Berzelius has published a paper in the 61st volume of the "Annales de Chimie," in which he states, fluoric acid may be detected in human teeth, bones, urine, and may be demonstrated, in the latter case, by operating on the precipitate obtained from the excretion by means of lime-water. Since the publication of this paper by Baron Berzelius, the existence of fluoric acid, as a constituent of the animal substances above mentioned, has been acknowledged by chemists generally; and it is mentioned as such in the standard chemical works of the present day.

Having lately been engaged in the analysis of human bone, with more especial reference to those ingredients which have been stated to exist in small proportion, I was led to search particularly for fluoride of calcium. My experiments were made in the usual manner, by trying to obtain the corroding action of fluoric acid on a plate of glass, which was used as a loose cover to a platinum crucible, which contained the substance for examination, mixed with strong sulphuric acid. A gentle heat was applied to the bottom of the containing vessel. In this way, several specimens of human bone (both before and after calcination) were subjected to experiment; but in no instance could I obtain any action upon the glass.

The experiment which the Baron recommends, in order to obtain corrosion from bone earth, is, to distil equal parts of strong sulphuric acid and water upon it, until the measure of water is brought over. He states, that the distilled liquor, if evaporated in the glass receiver, will produce a corrosion. I repeated this experiment, using 100 grains of bone-ash, and an ounce of the acid mixture; but could obtain no action on the receiver, by evaporating the distilled liquor; nor was there any corrosion or opacity produced on any part of the apparatus. During the evaporation of the last portions of the liquor, dense white fumes appeared; and there was some difficulty in vaporizing the whole of it. On neutralizing a portion with ammonia, and testing it with nitrate of silver, a yellow preci

pitate of phosphate of silver was thrown down. A further examination shewed the presence of sulphuric acid, and traces of hydrochloric acid. I was much surprised to find phosphoric acid in this result of aqueous distillation, as the heat had not been urged during the process; for I had considered that acid was of too fixed a nature to volatilize with water at so low a temperature. It appeared to me now, that the presence of phosphoric acid, in this distilled liquor, might be a source of fallacy in the above experiment for establishing the presence of fluoric acid as a constituent of human bone; for it is a well known fact, that phosphoric acid, if heated on glass of inferior quality till it volatilize, will act upon it with considerable energy, and all the animal substances in which fluorine has been said to exist, are particularly rich in phosphoric acid ;thus the ashes of ivory, of human bone, and the enamel of teeth, as also the precipitate obtained from urine by means of lime-water, are all of them composed, in very great part, of phosphate of lime.

Mr Richard Phillips has mentioned (in the Annals of Philosophy, Vol. v.), that when the water contained in uranite is driven off from the powdered mineral, a portion of the phosphoric acid is volatilized with it; the heat used being that of a common spirit-lamp. This is the only fact with which I am acquainted (with the exception of my own observation), to shew that phosphoric acid will volatilize with water. The heat used in Mr Phillips's experiment was, most probably, considerably higher than any which I applied. There seems no doubt that phosphoric acid is much more volatile than it has heretofore been supposed. Having failed in detecting fluoric acid in human bones, I determined on testing for its presence in the enamel of teeth, in recent ivory, and in the precipitate obtained from urine by the addition of lime-water. Two different specimens of ivory (tusks of the elephant) gave no evidence of the presence of fluoric acid, when carefully tested,

* It must be borne in mind, that the fluoric acid acts with facility on every kind of crown or flint glass, however good their quality may be. The supposition that bad glass was used in the experiment, is the only means I have of explaining away that which I feel sure is an error on the part of - several continental chemists.

either before or after calcination; and I was equally unsuccessful with the enamel of human teeth, and the precipitate from the urine.*

In these experiments, when I had failed in acting on the glass, I always found that the addition of 0.3 grains of fluoride of calcium to the experiment, produced a strong and indelible mark on the surface of the glass test-plate. I mention 0.3 grains, because it will always be found sufficient to produce a most unequivocal corrosion, though I obtained satisfactory results by the addition of a much less quantity. I have had only one opportunity of examining fossil ivory; and in that instance, I could not ascertain its locality. On submitting it, however, to the test used for recent ivory, bone, &c., I obtained immediate action on the glass. In conclusion, I must express my firm conviction, that fluoride of calcium, as an ingredient in fossil ivory, must be regarded as an extraneous matter, introduced by the partial mineralization of the animal substance ;—that no such constituent exists in recent ivory, the enamel of teeth, human bone, or urine;-in fact, that fluoride of calcium should be expunged from the list of the constituents of animal substances.

August 1839.

Sketch of Animal Life in Nova Zembla (Novaïa Zemlia.) By K. E. Von Baer.†

THE entire absence not only of trees, but also of every shrub which, without being sought for, might yet be sufficiently large to attract the eye, communicates to polar landscapes a peculiar and impressive character.

First of all, the power of measurement by the eye is lost, for, owing to the want of the usual objects of known dimensions, viz. trees and buildings, distances seem less considerable

I was much pleased to observe that Mr Pepys, in an analysis of enamel, published in Mr Fox's work on the Teeth, does not mention fluoride of calcium as an ingredient of that substance. This analysis was made by Mr Pepys in 1833, several years after the fluoride had been declared a constituent of the enamel.

↑ From " Wiegmann's Archiv für Naturgeschichte." 1839. Part II. p. 160.

than they really are, and even mountains appear to be of lower altitude. This remark has been often made and was not unknown to me, but, nevertheless, I found the deception, for which I was prepared, much greater than I had anticipated. I knew well, that from this cause alone, an expedition sent out by King Frederick the Second, from Denmark to Greenland, had failed in accomplishing its object. Mogens Heinson, who has always been regarded as an able seaman, commanded the ship, and, having come within sight of the coast of Greenland, steered directly for it with a favourable wind; but after sailing for several hours in the same course, thought that he approached no nearer to the shore. He became alarmed that some hidden power at the bottom of the sea detained him, and turned his vessel towards Denmark, whither he carried the report that having been attracted by a magnetic rock, he had not been able to reach the coast of Greenland. I was also acquainted with the naïve remark of Martens on Spitzbergen. "The miles appear quite short, but, when we come to walk them on land, they seem very different, and soon cause fatigue;" yet after all, the deception was so complete, that no reflection could remove it. I am likewise convinced that it depends not only on the want of the customary objects, but also on a peculiar transparency of the atmosphere, for on dull days it is not so perfect as on clear, and is not so striking in flat as in mountainous districts. On bright days, or at clear periods of the day, the air seems to be almost entirely colourless, and, as the heights visible to the eye are partly covered with snow, and partly exhibit a dark, and from the contrast, apparently a very dark coloured rock, the slight colour possessed by the air cannot be recognised. The mountains therefore seem to approach quite near to the spectator, and probably most so to those who have been accustomed to view mountains through a different kind of atmosphere.

Another effect of the want of trees, shrubs, and even grasses of considerable size, is the feeling of loneliness which seizes not only the man of reflection, but even the rudest sailor. There is nothing painful in this sensation; for it is of a solemn and elevating character, and can only be compared to that powerful impression which a visit to Alpine heights leaves in