forces which act on the other wheels, they can noway

the going of the watch.

affect

The Author adds an account of another inftrument which he has invented, and fent along with the Proportional Compaffes to the Royal Society; but the vague manner in which he speaks of it, joined to the want of a drawing, renders it impoffible for us to form a juft idea either of its conftruction or merits. He concludes his paper with tables of the dimenfions of the feveral pinions generally ufed in clock and watch work, according to the principles which he has before laid down. CHEMISTRY.

Article 39. Chemical Experiments and Obfervations on Lead Ore. By Richard Watfon, D. D. F. R. S. &c.

In this paper, Dr. Watson first takes notice of the difference in the specific gravities of various lead ores, and even of different parts of the fame lump of ore. Notwithstanding this circumftance, we are told that the purchafing of lead ore by the measure, is the general, though not the universal custom in Derbyshire. To find whether the fulphur with which lead is generally mineralifed in the ore (particularly in the steelgrained and teffelated galenas) could be feparated from it in clofe veffels, or by distillation, as is the cafe with respect to fome kinds of the pyrites; he diftilled 16 ounces of fome teffelated Derbyshire lead ore in an earthen retort. Though he gave the retort a white heat, no fulphur was fublimed: but the ore loft a 32d part of its weight. The matters feparated from the ore were-a fmall quantity of a black fubftance, that rose up into the neck of the receiver; and which appeared to be pure lead ore, fublimed without being decompounded :-a small portion of a liquid, that had a pungent fmell, refembling that of the volatile vitriolic acid, and which had an acid tafte; though it did not effervefce with alcalis, nor produce any change in the colour of blue paper:-and lastly, a quantity of air or elaftic fluid; which, at the beginning of the procefs, had the smell of inflammable air. In the following experiment, however, he not only feparated the fulphur from the ore, but was enabled to afcertain its quantity.

Five ounces of the ftrongest fuming fpirit of nitre, diluted with an equal quantity of water, were poured on ten ounces of lead ore. A violent effervefcence enfued; and when the folution was completed, there remained floating upon the furface of the menftruum, a cake of fine yellow fulphur, perfectly refembling common fulphur. This fubftance, edulcorated and dried, generally amounted to one-third of the weight of the ore.

This matter however is not pure fulphur, but is a mixture of that fubftance and a calx of lead: for on putting fome of it on a red hot iron, a greyish calx remains, after the fulphur is confumed;

confumed; which on being put on a piece of ignited charcoal, is reduced, at least in part, to a metallic ftate. The Author confidering the great quantity of fulphur contained in the Derbyshire lead ores, where about 10,000 tuns are fmelted annually, proposes to the confideration of the lead fmelters the practicability of collecting it; both as a lucrative business to themselves, and a great faving to this country, where, it seems, we at prefent import the fulphur we use. For this purpose, he fuggefts the poffibility of collecting it, in long, large, and winding horizontal chimneys, connected with the furnaces in which the ore is roafted in the fame manner as is practised in Saxony, where arfenic is procured by a fimilar contrivance; the arfenical vapour being condenfed, and attaching itself, like foot, to the fides of the chimney; from which the arfenic is, from time to time, fwept out.

At the end of this paper, the Author relates fome experiments from which it appears that, though the furface of pure melted lead becomes covered with a pellicle of various colours; yet thefe appearances do not occur if a small portion of tin be mixed with the lead, even when the weight of the tin scarce exceeds the bath part of the weight of the lead. Zinc poffeffes the fame property, in this particular refpect, as tin. After the tin has been reduced to a calx, by the continuance of the heat, the lead again acquires its property of forming colours; which fucceffively appear in the following order: yellow, purple, blue, yellow, purple, green, pink, green, pink, green. The rationale of these appearances may be deduced from the well-known experiments and theory of Sir Ifaac Newton, lately illuftrated and confirmed by Mr. Delaval, in his ingenious Experimental Enquiry refpecting the changes of colours in bodies.

MISCELLANEOUS ARTICLES. Article 26. An Account of the Island of St. Miguel. By Mr. Francis Maffon.

This island is one of the principal of the Azores. The only particulars relating to it, that can entitle this account of it to a place in the Philofophical Tranfactions, are contained in a general defcription of fome fountains, from which the water boils up fo hot, that a perfon cannot dip his finger into it without being fcalded.' A fteam likewife rifes, to a confiderable height, from feveral apertures, which is fo hot, that no one can approach it with the hand. In other places, fays the Author, ⚫ a perfon would think that a hundred fmiths bellows were blowing altogether, and fulphureous fteams iffuing out [iffue out] in thousands of places, fo that native fulphur is found in

* See an account of that work in the 57th volume of our Review,

P. 221.

Rev. Jan. 1778.

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every

every chink, and the ground covered with it like hoar froft; even the bushes that happen to lie near these places are covered with pure brimftone, condenfing from the fteam that iffues out of the ground, which in many places is covered over with a fubftance like burnt alum.' Though the Author appears to have been in poffeffion of a thermometer; no account is given of the actual temperature of these waters.

Near these boiling fountains, there are feveral cold mineral fprings; two of which are faid to fend forth waters which have a very ftrong mineral quality, of an acid tafte, and bitter to the tongue.'-Seven fpecimens of these and other waters have been fent home, and are enumerated at the end of this Article. The first of these was taken from one of these cold fountains; which is described as giving a strong acid water.'-As this ftrong acid water appears to us a very great curiofity, we could have wished that its analyfis had been fubjoined to this Article; as well as, indeed, that of the hot waters above mentioned, which are faid to poffefs confiderable virtues in the cure of the dead palfy, eruptions, and more particularly the gout. While the Author refided near thefe waters, feveral old gentlemen, who were quite worn out with the faid diforder, were using the waters, and had received incredible benefit from them.' He accordingly hints, that fhould any perfon venture fo far for his health, a small stock of the fuperfluities of life only need to be laid in, as the island yields every neceffary,' and the climate is very temperate.

Article 27. An Account of a remarkable Imperfection of Sight. In a Letter from Mr. J. Scott, &c.

The perfon who here communicates feveral extraordinary particulars of an bereditary infirmity in the vifual organs, with refpect to colours, can fee objects at a diftance, and distinguish their form and bulk as well as moft men: but fuch is his fingular idiosincrafy with respect to their colour, that he declares, though his bufinefs was behind a counter many years, where he had to do with a variety of colours' he does not know any green in the world; a pink colour, and a pale blue are alike. He has often thought a full red and a full green the fame, or a good match: though he can difcern the difference between yellow and a full blue. He relates an anecdote of his having been offended at an intended fon-in-law's having entered his house, on the day preceding his marriage, in a new fuit of cloaths, which appeared as much a black to his eyes, as any black that ever was dyed; while the gentleman had actually decorated himself with a fine rich claret-coloured dress."

We have called this imperfection hereditary; but, like fexdigitifm, it appears to have affected only fome individuals of his family. He derived it from his father; but his mother had

not this imperfection, and yet her own brother had the like impediment with himfelf. This is fomewhat fingular; unless his father and mother were related to each other before marriage. One of his fifters knows colours, the other does not; the laft has two fons who have this imperfection, and a daughter who is free from it. His own fon and daughter know all colours without exception.

Article 40. Defcription of a most effectual Method of fecuring Buildings against Fire, invented by Charles Lord Viscount Ma hon, F. R.S.

As it is impoffible to abridge this intercfting Article; and as the noble inventor has not in it explained the principles on which his method is founded; we fhall confine ourselves to his account of two trials of it, made in the prefence of the Prefident and fome of the Fellows of the Royal Society, the LordMayor and Aldermen of London, feveral of the foreign minifters, and others.

The lower room of a building, which was about 26 feet long, by 16 wide, was filled with fhavings and faggots, which were fet on fire. The heat was fo intenfe, that the glafs of the windows was melted, like fo much common fealing-wax, and run down in drops; yet the flooring boards of that very room were not burnt through, nor was one of the fide timbers, floorjoifts, or cieling-joifts, damaged in the finalleft degrce; and the perfons who went into the room immediately over the room filled with fire, did not perceive any ill effects from it whatever; even the floor of that room being perfectly cool during that enormous conflagration immediately underneath.'

To reprefent a timber-built town on fire, and to fhew how effectually even a wooden building, fecured in this manner, would ftop the progrefs of the flames; a kind of timber building (of full 50 feet in length, and of three stories high in the middle) had been erected, quite clofe to one end of the fecured wooden house. The former was filled and covered with above 1100 large kiln faggots, and feveral loads of dry fhavings; and the whole pile was fet on fire. The event is thus related:

The height of the flame was no less than 87 feet perpendicular from the ground; and the grafs upon a bank at 150 feet from the fire was all fcorched: yet the fecured wooden building, quite contiguous to this vaft heap of fire, was not at all damaged, except fome parts of the outer coat of plafter work.'An attempt was next made to burn a wooden ftaircafe, fecured according to the inventor's method: but it refifted the flames, as if it had been conftructed of fire-ftone. Since this experiment, five other, ftill ftronger, fires have been made on and under it; the whole fpace having been filled with fhavings

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fhavings and large faggots: but this Afbeftine ftair-cafe is ftill ftanding, and is but little damaged.

The noble Inventor of this method propofes, in a fhort time, to give the world an account, in detail, of many other experiments on this important fubject; and of the application of his method to different kinds of buildings, and to the different conftituent parts of a houfe. He means likewise to add a full explanation of the principles upon which it is founded, and the reasons for its certain and surprising success.

Article 50. Track of his Majesty's armed Brig, Lyon, from England to Davis's Streights, and Labrador, &c. By Lieutenant Richard Pickerfgill, &c.

This Article is digefted in a tabular form, and contains the daily obfervations made for determining the longitude by the fun and moon, the error of the common reckoning, the variation of the compass, dip of the needle, &c. as obferved during the voyage in 1776. At the end of the paper, the Author,' without meaning any perfonal reflection,' animadverts on the accounts given by others of this part of the world, fo little known, and fo terribly reprefented. Having heard fuch dreadful ftories of these countries,' he adds, I cannot help remarking it, as a circumstance equally foolish and ridiculous; tending to mislead those who, from a laudable principle, would be benefactors to their country, but are deterred from it by fuch reprefentations and he declares his intention of publishing, in a fhort time, his obfervations on the ice, the atmosphere, the land of Forbifher, and the probability of a North-west paffage *.

The remaining papers in this volume are-Article 28. Containing an Account of Baptifms, Marriages, and Burials, during 40 Years, in the Parish of Blandford Forum, Dorfet; by Richard Pulteney, M. D. F. R. S.; where it appears that, on an average, there only dies 1 in 39 yearly.-Art. 30. Aftronomical Obfervations made in the Auftrian Netherlands, in the Years 1773, 1774, and 1775; by Nathaniel Pigott, Efq; F. R. S. &c.-Art. 34. An Account of the Blue Shark, together with a Drawing of the fame; by W. Watfon, jun. M. D. F. R. S.Art. 35. A Defcription of the Exocœtus Volitans, or Flying Fish;

It is to be feared that we fhall have no more of thefe papers: Mr. P. lately loft his life by the overfetting of a boat on the Thames, as he was going on board a privateer, of which he had the command. The mention of this accident, naturally fuggefts to us the melancholy idea of a ftill greater lofs which the public hath sustained by the unfortunate death of, perhaps, the greatest navigator that ever exifted: Need we add the celebrated name of Capt. Cook ?— The reft was told in the London Gazette of January 11, 1780.

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