fame fort of blue, though not fo good.

Hence we may conclude, that the falt of the first experiment, which was produced by three drams of spar with acid of vitriol, contained thirteen grains of vitriol of iron.

Pruffian blue, made without help of allum, contains nearly half its weight of iron. Hence, from the foregoing experiments, three drams of this fpar contain gr. viii. of iron, 3j. and gr. xlix. of calcareous earth, and 3j. gr. iij. of the earth of sal catharticus amarus, or perhaps fome other earth, which forms, with acid of vitriol, a foluble falt.

The spathofe iron ore being frequently found crystallized like the foregoing new spar, and having also a gloss on it, I was willing to try whether it had any affinity with it; but by the following experiments it appears to be of a different nature, not containing any calcareous earth.

.The fpathose iron ore diffolves almost totally in acid of falt, and the solution is of a deep yellow colour. A folution of tartar of vitriol in water added to it causes no precipitation; and hence it is evident, that it contains no calcareous earth. Acid of vitriol treated with the spathofe iron diffolves the whole of it, excepting a few dregs; another proof of its containing no calcareous earth. The acid of nitre diffolves alfo this fpar, and the folution is colourlefs.

[ 35 ]
L

IV. Account of a Petrefaction found on the Coast of East

Lothian.

By Edward King, Esq. F. R. S.

TO SIR JOHN PRINGLE, BART. P. R. S.

SIR,

Read Nov. 26, 1778.

N consequence of the honour

IN

to put into my hands a very curious specimen of a recent petrefaction, permit me now to offer to your confideration a few thoughts concerning this production, which have occurred to me on comparing it with others of a similar kind, and which may at least serve as hints for further investigation.

We should not venture, it is true, without great caution, to fpeculate on these matters, as hafty and fpecious conclufions may easily be drawn by any one who indulges too readily a quick and lively imagination, which will ever be too ready to mislead, rather than to procure folid information. But though I

am well aware of this danger, yet I venture to lay before you these few obfervations; and if you judge them at all worthy of attention, I would wish to communicate them, through your hands, to the Royal Society, for they are not made merely in confequence of a flight and hasty furvey of this one specimen, but are in truth conclufions that I have been led to form incidentally in the course of a very long inquiry, which I have been for fome years pursuing on another occafion; the result whereof I shall perhaps, if I live, hereafter communicate to the Society in a more full and explicit manner than the compass of a paper of this kind will permit.

The account of this fpecimen, with which you favoured me, is as follows. In the year 1745, the Fox man of war was unfortunately, ftranded on the coast of East Lothian in Scotland, and there went to pieces; and the wreck remained about three and thirty years under water; but this last year a violent storm from the Northeast laid a part of it bare, and several maffes, confisting of iron, ropes, and balls, were found on the fands near the place, covered over with a very hard ochry substance, of the colour of iron, which adhered thereto so strongly, that it required great force to detach it from the fragments of the wreck. And, upon examination, this fub

4

ftance

stance appeared to be fand, concreted and hardened into a kind of stone.

The specimen now laid before the Society had been taken out of the fea, from the fame spot, fome time before, and is a confolidated mafs that had undergone the fame change. It contains a piece of rope that was adjoining to some iron ring, and probably had been tied thereto. The fubftance of the rope is very little altered; but the fand is fo concreted round it, as to be as hard as a bit of rock, and retains very perfectly impreffions of parts of the ring, just in the same manner as impreffions of extraneous foffil bodies are often found in various kinds of ftrata.

Now, confidering these circumstances, we may fairly conclude, in the first place, that there is, on the coasts of this island, a continual progreffive induration of maffes of fand and other matter at the bottom of the ocean, fomewhat in the fame manner as there is at the bottom of the Adriatic sea, according to the account given by Dr. DONATI(a).

And, in the next place (which is what more particu larly deserves our attention on this occafion), it should feem, that iron, and the folutions of iron, contribute very much to hasten and promote the progress of the concre◄ tion and induration of stone, whenever they meet and are (a) See the Phil. Tranf. vol. XLIX. p. 588.

united

united with thofe cementing cryftalline particles, which there is reason to believe are the more immediate cause of the confolidation of all ftones and marbles whatfoever, and which do very much abound in fea water.

It would exceed the limits of this paper, were I to attempt here to mention only a small part of the various facts that have come to my knowledge; and which have convinced me, and I truft, when offered fairly to the confideration of others, will make it appear fully to all that are attentive to these kind of researches, that there is, to this very day, a formation of ftone, and even of marble itself, in certain places, in a much more perfect manner, than has been generally conceived; and far beyond what has been supposed, even by those who have been ready too hastily to account for such a process merely in confequence of obfervations made on stalactitical and fuch like ordinary concretions.

I shall not therefore prefume to trouble the Society, at present, with any detail of the inquiries I have made relating to that subject, though in reality they have been the foundation of the obfervations made in this paper; but shall confine my remarks merely to this one curious circumstance; that wherever there is any induration and petrefaction of matter, from any causes whatever, it is greatly haftened in its progress, and the confolidation is rendered much more compleat and firm by