The smell and taste was similar to that of Harrowgate water, but accompanied with less sparkling. Its volatile parts dissipated by exposure to the atmosphere, and formed a thin pellicle of sulphur on the surface. The colour of a bright silver table spoon was sensibly changed when suspended in the vapour, and the surface of a penknife was readily acted upon when immersed in the water. Boiling entirely deprived it of smell. The water is taken internally from 7 to 10 in the morning and evening, which is usually the time for bathing. The company employ these intervals in promenading to the dismal light of two or three lamps. The utmost precaution is observed in protecting the body by warm cloathing, which is here very necessary. The insipidity of social intercourse, added to a total defect of public amusement, present no inducements to the residence of a stranger. The climate is subject to extreme variations of temperature, and the prevalence of violent winds in the spring, which blow uninterruptedly from the ocean. The excessive heat of the summer season in the day time, is succeeded by cold moist vapours in the evening, which render an exposure of the body extremely hazardous. On the 23d of August, the thermometer in the shade at mid-day, indicated 78° Fahr. and in the sun 115°, giving a difference of 37°. At midnight it was 44°, giving a difference of 34° between the temperature of mid-day and midnight. There are four baths appropriated to public use. But the principal one, or men's bath, is the one from which the sample was taken. It is 36 feet long, 9 feet wide, and about 2 feet 10 inches deep. It is enclosed by a spacious vaulted apartment. The spring oozes from the north-west corner, yielding upwards of 45 cubic feet per minute, calculating from the rise of water in the bath. A pump is placed in the source for the purpose of applying a stream on the different parts of the body. A thermometer plunged immediately into the source, indicated a temperature of from 93° to 94°, which agrees with the statement of Dr. Withering. The east end, which is most remote, varied by several degrees. A fine white sand over a stratum of argillaceous earth, covers the bottom

of the bath on which the bathers' sit. An inclined board admits of the requisite elevation to bring the chin on a level with the surface of the water. An attendant regulates the period of immersion according to the nature of the patient, and renders every assistance for a small gratuity, which is perfectly optional to the bather. An apartment properly heated, is appropriated to the general service of dressing and undressing, and the usual precautions observed before and after bathing. The women's bath is about the same size, but from the room being larger, the average temperature of the bath is lower. The thermometer indicated the same temperature in the source. The product of the supply of the men's bath, is equal to the united products of this and the other two. The waste water of all the sources, is conducted westward into the cistern at the king's garden, where it serves the purpose of bathing cattle, and turning an horizontal water-wheel by the lateral impulse of the water, and as the wheel revolves with great rapidity, the prolonged axis of it moves the upper millstone with sufficient velocity. Most water-mills in Portugal are constructed upon this principle. The garden, or quinta, although in bad taste, is large and well kept. From May to September may be accounted the fashionable season. From vestiges of Roman antiquity discovered on the scite of the present establishment, it is probable, that the Romans were acquainted with the medicinal properties of these springs, but their history is involved in obscurity, until the marvellous virtues attributed to them attracted the notice and piety of Eleonor, (queen and consort of Dom John II.), who erected an hospital for the benefit of poor persons, in the year 1484, and hence the denomination of Caldas de Rainha, or Queen's Hot Baths. The first attempt at an analysis of this water was made at the university of Coimbra, in the year 1776, and afterwards by Dr. Nunez Gayo, in a memoir intitled Tratado da Ague de Caldas da Rainha, Lisboa, 1779, 8vo. The result of his experiments gave the following ingredients:

Iron, marine salt, the elements of phlogiston, selenites, fixed air, absorbent earth, argil.

Agreeing with the experiments made at Coimbra, with the exception of the presence of iron, not detected by that university, a small pamphlet was published in the year 1791, 4to, on the use and abuse of Caldas waters. "Advertencias sobre os abusos e legitimo uso dos Agoas mineraes dos Caldas da Rainha, por Francisco Tavares, Lisboa, 1791." Little information, however, can be derived from the above authorities, exhibiting throughout an imperfect knowledge of chemical science.

In the year 1795; a pamphlet was published by the celebrated Dr. Withering, of Birmingham, entitled, "Analyse da Agoa da Caldas da Rainha," &c. 61 pages, 4to. The work is entitled to much attention, as being the only considerable approximation hitherto made towards a knowledge of its component parts, but which this skilful naturalist was prevented from correctly ascertaining by the imperfection of his apparatus.

I remain your most obedient,

GEORGE RENNIE.

Dr. Withering's analysis of 128 oz, of the water is as follows:

Some of the water brought to England was found to be of

specific gravity 1005, 8.

16 ounces evaporated gave 24 grains of dry salts, and they were

ART. VIII. Report of Mr. Brande's Lectures on Mineralogical Chemistry, delivered in the Theatre of the Royal Institution, in the Spring of 1817. Continued from page 247 of Vol. IV.

Don

THE mineralogical and chemical history of platinum, copper, and mercury, formed the subject of the next lecture. Platinum has been known in Europe for about a century. Antonio de Ulloa, who accompanied the French Academicians to Peru, for the purpose of measuring a degree of the meridian in 1735, is the first who formally announces it by name; and in 1754, its properties were very diligently examined by Dr. Lewis, and an account of them published in his "Philosophical Commerce of the Arts."

This metal may be considered as the exclusive product of South America, having been hitherto only found in New Granada, in the province of Barbacoas, near the shores of the South Sea, and in Brazil. Vauquelin indeed, has lately detected it in very minute quantities in the gray sit ver ore of Guadalcanal.

It occurs in small grains, very heavy, an d of a silvery white lustre these, however, besides platinum, contain a variety of other bodies. The pure metal may be procured by dissolving

the ore in dilute nitro-muriatic acid, precipitating by sa' ammoniac, and heating the precipitate to redness. Granulated platinum is thus obtained, which at a white heat may be welded into bars. It is a white metal, sp. gr. 22, very ductile and malleable. Dr. Wollaston, by the ingenious expedient of enveloping it in silver, has drawn it into wire, one twothousandth of an inch only in thickness. It is very difficult of fusion, and a bad comparative conductor of heat and electricity; hence in the Voltaic circuit it sooner becomes red-hot than most of the other metals. The chemical properties of platinum were next shewn, the means of recognizing it in analysis pointed out, and the method exhibited of applying it to the surface of porcelain and earthen ware.

The chemist is the principal person who has been benefited by the discovery of platinum. Its power of resisting the action of heat, and of most acids, renders it very valuable for many purposes in the laboratory; there are, however, many bodies which unite with it at a moderate temperature, forming an easily fusible compound, and the introduction of these into vessels of platinum, must be carefully guarded against.

Although the metallic grains whence we obtain platinum consist chiefly of that metal, they also contain gold, iron, lead, generally mercury, and four other metallic bodies, which are of more recent discovery, and have been termed iridium, osmium, palladium, and rhodium. Of these, the two former were discovered by the late Mr. Tennant, and the two latter by Dr. Wollaston; and had we searched throughout chemistry for an illustrative instance of the delicacy of the modern art of analysis, it would be difficult to have found any one more notorious than the history of the discovery and separation of these bodies exhibits.

When crude platinum is acted on by nitro-muriatic acid, by far the greatest proportion is dissolved; but there remains a black powder, which was taken by Mr. Tennant as the subject of his researches, who found that by the alternate action of soda and muriatic acid, it might be entirely dissolved.