and have made ufe of this, already, familiar to us, and which feems liable to no objection, fince it is not confined to any particular fpecies.*.

The following experiments were performed with various kinds of whin ftone, and have likewise been extended to lava. To investigate the relation between thefe two claffes of fubAtances, feems, in the prefent ftate of geology, an object of confiderable importance; for they refemble each other in fo many refpects, that we are naturally led to afcribe the formation of both to the fame caufe, and to believe that whinflone, as well as lava, has been expofed to the action of heat. In the courfe of the paper, I fhall mention feveral accidental refults, which, if confidered feparately, might feem unworthy of notice, but which, by affording the means of comparifon between the two claffes,, are of great fervice in the general inveftiga-,

tion.

The whinftone firft employed was, taken from a quarry* near the Dean, on the Water of Leith, in the neighbourhood of Edinburgh. This ftone is an aggregate of black and greenish-black hornblend, intimately mixed with a pale reddish-brown matter, which has fome refemblance to felf par, but is far more fufible. Both fubftances are imperfectly and confufedly cryftallized in minute grains. The hornblend is in the greateft proportion; and its fracture appears to be ftriated, though in fome parts foliated; that of the reddish-brown matter is foliated. The fracture of the ftone en maffe is uneven, and it abounds in fmall facettes, which have fome degree of luftre. It may be fcratched, though with difficulty, by a knife, and gives an earthy fmeil

when breathed on. It frequently cantains fmall fpecks of pyrites.

On the 17th of January 1798, Į introduced a black lead crucible, filled with fragments of this ftone, into the great reverberating furnace at Mr Barker's iron foundry. In about a quarter of an hour, I found that the fubftance had entered into fufion, and was agitated by a strong ebullition. I removed the crucible, and allowed it to cool rapidly. The refult was a black glass, with a tolerably clean fracture, interrupted however by fome fpecks.

In fubfequent experiments, 1 endeavoured, by flow cooling after fufion, to prevent, the whinstone from becoming vitreous, and to compel it to refume its original character by cryftallization. In this I fo far fuc ceeded as to obtain a fubftance, which was not glafs, though it did not posfels the properties of whinftone. The production of this intermediate subftance, which much refembled the liyer of an animal, is accompanied with fome curious particulars, which I, fhall enumerate and explainin another part, of this paper. On fome occafions, too, I obtained a vitreous mafs, in which were a multitude of little fpheres, having a dull or earthly fracture.

At last, on the 27th January, I fucceeded completely in the object I had in view. A crucible, containing a quantity of whjoftone, melted in the manner above defcribed, being removed from the reverberatory, and conveyed rapidly to a large open fire, was immediately furrounded with burning coals, and the fire, after being maintained feveral hours, was allowed to go out. The crucible, when cold, was broken, and was found to contain a fubitance, differing in all reSpecta

+ Called Bell's Mills Quarry.

fpects from glafs, and in texture completely refembling whinftone. Its fracture was rough, ftony, and cryftalline; and a number of fhining facettes were interfperfed through the whole mafs. The cryftallization was ftill more apparent in cavities produced by air bubbles, the internal furface of which was lined with diftinct crystals*.

Having fhewn this refult to feveral of my friends, Dr Hope regretted that the fubftance, previously to its artificial crystallization, had not been reduced to the ftate of folid glass; fince the adverfaries of the fyftem might alledge, that, during the action of heat, the original cryftallized texture of the ftone had never been com pletely deftroyed. Being convinced of the propriety of this obfervation, I determined, in future, to reduce the ftone firft to glass, and to perform the cryftallization after a fecond fufion.

For this purpose, with the affit ance of Dr Kennedy, to whofe cooperation I am greatly indebted for the fuccefs of all the following experiments, reduced a quantity of the fame whinftone to moft perfect black glafs. A crucible, filled with fragments of this glafs, being then expofed to a heat, which, from previous trials, was judged to be more than fufficient to reduce its contents to fufion, the fire was very gradually lowered till all was cold. I thus ex pected to obtain a refult fimilar to that last mentioned, but found, to my great furprife, that the fragments had never been in complete fufion, fince they fill, in a great meafure, retained their original shape. This extra

ordinary fact, which afterwards led to the difcovery of fome curious properties of whinftone, will be fully accounted for in a fubfequent part of the paper.

Another portion of the fame glafs being perfectly melted by a very ftrong heat, the temperature was reduced to about 28 of Wedgwood, and was maintained at that pitch during fix hours. The refult was a perfectly folid mafs crystallized to a certain depth from the outside, though still virteous in the heart.

In another experiment, performed like the laft in all refpects, except that the heat was maintained at 28 during twelve hours, I obtained a mafs entirely cryftalline and tony throughout, with facettes appearing in the folid parts, and small cryftals fhooting into fome of the cavities.

Soon after I had communicated these refults to Dr Hope, he performed, with complete fuccefs, an experiment fimilar to the first, in which I had obtained a crystallized fubftance, by the gradual cooling of the melted flone. The fame wast likewife, foon afterwards, performed by Mr Bofwell of Auchinleck.

My experiments, already defcribu ed, were confined to one fpecies of whinftone, but have fince been ex-Ń tended to fix other varieties. Theyli were all firft reduced to glafs by the application of a strong heat, and fub- fequent rapid cooling. After a fecond fufion they were cryftallized, by being kept long in a ftationary temet perature, between 28 and 35. This laft operation was beft performed in a long and narrow muffle, wholly

furround

furrounded with burning coals, according to a practice long followed by Dr Kennedy, by which the heat

could be maintained with fo great fteadiness as to render the refult almoft certain.

AT

T Buffora, the traveller fhould equip himself like the Arabs. It will be neceffary for him, as foon as he embarks, or even before, to fuf. fer his beard to grow; but, as it may be uncomfortable to wear his beard at full length, it will be fufficient if he do but preferve his muftachoes. This, however, must be particularly attended to, and can by no means be difpenfed with; for, though a man without a beard might be fafe in a large city, or in any civilized place, yet in a journey of this nature, wherein he will often meet with barbarous wandering tribes, who would not hefitate a moment about putting him to death if they should discover that he was a Fringui*, he will perceive the neceffity of imitating the Arabs in drefs as nearly as poffible.

As few Europeans have any knowledge of the Arabic language, particularly as it is spoken in Arabia, he will be much at a lofs, especially when he has none but Arabs about him. He will, therefore, find it useful to have with him a kind of vocabulary, to enable him to afk ufeful or neceffary questions.

When the traveller arrives at Bagdad, he will find that the English are more refpected than any other nation; he will therefore feel the neceffity of acting in the most honourable manner in every transaction, that he may fupport the dignity of the national character; for fuch is the illiberal way of thinking among these people,

that, should an individual of any country act meanly, the people would condemn all his nation; and the bad conduct of one perfon might thus endanger the lives of hundreds of his countrymen, who might adopt the fame route.

From Bagdad there is but one mode of travelling, which is under the guidance and protection of the Tartars, or meffengers of government. These men are under the immediate' order of the Bafha and his minifters; but are at all times ready to enter into any contract with an individual, which they ufually make very profitable to themselves, particularly when they have to conduct thofe who are enabled to obtain firmauns †; for, by virtue of thefe, the Tatars are enabled to take feveral horfes and attendants, and a large quantity of merchandise on their return, which pays them very well. In the Author's firmaun it was intimated that he was an English Conful, which enabled his Tatar to obtain guards (free of expence) whenever there was danger to be apprehended from the wandering tribes. This is by far the fafélt way of travelling, as the perfon of a conful is feldom infulted.

Great care fhould be taken when an agreement is about to be made with a Tatar. It is advifable to pay him only half of the money agreed for at Bagdad, that he may have an intereft in delivering the traveller fafe at Conftantinople. Care fhould

be

tars.

be taken alfo, that the Tatar does not engage to carry merchandize for any one, which he will do if poffible. The neceffaries which the traveller takes fhould be compreffed into as narrow a compass as poffible. A little tea, coffee, and fugar, will be fervice able in the winter feafon; and fome fpirits, either brandy or hollands, may be useful; but he thould by no means be encumbered with either of these in, fummer.

The traveller fhould be equipped in the fame manner as the Tatar, which will always enfure him refpect. Some have attempted to travel under the character of the Tatar's fervants (the Armenian merchants in particular do this,) but the Author confiders it as too degrading for the character of an Englishman. The Tatars, who are accuftomed to travel. very faft, ufually ride the hindmoft horfe of the company, and whip the the other beafts to keep them going. This fhould never be permitted; but whoever attempts a journey of this kind fhould be a good horseman.

The traveller ought not to encumber himself with fpecie, except about half a dozen piaftres, to give as prefents to those who may render fome little fervices. He will, it is true, he often folicited for gifts, but fhould always refer the applicants to his Tatar; and when they find that, they will not apply a fecond time. It is much more prudent to take bills,

M

drawn by the merchants, which will ufually meet due honour, while they offer no temptation to robbers.

From Conftantinople, if the traveller be unacquainted with the language, it will be neceffary to engage a Janizary to conduct him to the frontiers, who will be paid in about the fame proportion as the Tatars.

It has often been a subject of inquiry, which is the speedieft method of forwarding dispatches to and from India? The Author is of opinion, that the route by which he came must be the moft expeditious for forwarding difpatches to India. When the meffenger arrives at Bagdad, he can. fet out immediately in a kiraffe down the Tigris till he reaches the Hie, down which he will proceed till he enters the Euphrates. By this channel he may be able to reach Buffora in three days, which must be much quicker than going by land to Hilla, and from thence down the Euphra-, tes.

The ufual mode of forwarding dif-. patches from India is by the way of Buffora, over the Great Defert to Aleppo; from thence to Conftanti. nople, and afterwards by the German. poft to Vienna and Hamburgh. This is certainly done at an eafy expence, and much lefs than by way of Bagdad; but the latter would, no doubt, be a quicker route in cafe of neceffi ty, as the Arabs are obliged to crofs the Great Defert on camels.

ELVILLE-Caflle, the Seat of the Right Honourable Henry Dundas, ftands in a low fituation, on the northern bank of the North Efk, near to the village and parish church of Laffwade, at the diftance of about five miles South West from Edinburgh and about three miles Weft from Dalkeith. It is not feen from any confiderable ditance. The ad. jacent grounds, on both fides of the river, advance boldly almoft to the very edge of the ftream; then terminating fomewhat abruptly, leave on

either fide a small extent of low-lying. level mead, between the defcent and the bank of the river. The tract of. level mead on the northern bank is the broadeft, and here ftands Melville Caftle. From the higher grounds immediately above, the profpect is, fufficiently rich, extenfive, and .varied. Some fine wood is fcattered near the Houfe, and round the Park.

In the prefent view, MelvilleCaftle is fuppofed to be feen from, the fouthern bank of the river, .on which it ftands.

ON