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muriate of magnesia, and sulphate of magnesia, may all be procured from these waters, there is no difficulty in accounting for the origin of each of these salts. The decomposition of the martial pyrites would furnish the carbonate of iron, which renders these waters so highly chalybeate; likewise the acid for the production of all the sulphuric salts, as well as the sulphur for the formation of the sulphuretted hydrogen found in these waters. The muriate of soda or common salt is doubtless coeval with the abundance of marine animal remains which are disseminated throughout the mass of aluminous earth, and came originally from the ocean— the sulphuric acid from the iron pyrites coming in contact with the magnesian limestone, will fully account for the presence of magnesia, and for the saline matter usually designated by the name of Epsom salt ; and as it is well known, that at a low temperature sulphate of magnesia will decompose muriate of soda, this will fully account for the origin of the alkali, which is the base of the sulphate of soda, or Glauber's salt, which always occurs in a state of solution in these waters.
From the best information which we have been able to obtain, we have learned that it is nearly one hundred years since the waters of Cheltenham w^re recommended for their medicinal qualities, and that the first well was railed in about the year IT 18.
For many years subsequent to this period, the properties of these waters were treated of by various medical writers; and between the years 1770 and 1780 they acquired so much reputation, that the town became a place of great resort for invalids, from all parts of the kingdom.
But as the celebrity of the waters increased, it was soon found that the wells could not supply the quantity which was required by the increased demand; and in the year I?88 a new well was sunk by order of his present Majesty, known by the name of the King's well. At first the supply from this well was very abundant, but it afterwards decreased so much, that it was often drank out by the company in half an hour.
The waters of all the wells having thus continued to diminish in quantity, serious apprehensions were entertained that the company which had been in the habit of visiting Cheltenham would meet with such frequent disappointments, from the failure of the springs, that they would be induced to look out for some other watering-place, and that in a short time the town would be entirely deserted by the strangers who had formerly visited it, either for the purposes of health or pleasure.
At this period a gentleman of the name of Thompson, who had purchased a great part of the land in the vicinity of Cheltenham, determined to search for mineral water upon his own estate, and to try to supply the deficiency so much complained of. The success he met with soon led him to think of turning this discovery to his own advantage, as well as that of the public; and accordingly a new pump-room was erected, and no exertions were spared, until water was obtained sufficient for the supply of whatever company might resort to the town and neighbourhood.
Mr. Thompson, foreseeing the advantages which might be derived from this inexhaustible source, now built a laboratory, for the purpose of concentrating the waters, and extracting the salts from them in a crystalline form. He soon found, however, that a large quantity of water would be necessary, for affording a constant supply to the boilera; and accordingly was obliged to sink many fresh wells before this object could be fully attained. For, owing to the tenacity of the clay, the water will not find its way through it, for any considerable distance, so as to percolate from one well to the other. In consequence of this, the proprietor was under the necessity of sinking upwards of seventy wells, and laying down several thousand feet of pipes, before he could obtain that full supply of water which the laboratory required.
Conceiving that it was desirable to give some account of the situation of the wells—of the different strata cut through —and of the variation in the water, at different depths from the surface—we have obtained from the proprietor an account of the results in sinking the well which is situated nearest to the laboratory, and this we copy, with the design of furnishing an idea of the nature of these wells in general.
After passing through the soil, they came to a bed of sand, which continued for twelve feet, at which depth fresh water was found; under this was a bed of blue clay, in which, at the depth of fifteen feet, or twenty-seven feet from the surface of the sand, a saline chalybeate water first made its appearance. This the workmen conducted into a distinct reservoir, cut on the side of the well, on purpose for its reception; and they arched it in such a manner, that a pump might be fixed in it so as to draw this water to the surface, without allowing it to mix with any other spring which might be discovered at a still greater depth. Having taken these precautions, the men then proceeded to sink lower ; and when they had cut through four feet more of the clay, they came to another spring, of the same nature as the former, but much stronger in its saline properties. A separate reservoir having been prepared in the side of the well for this water also, as in the former case, the men proceeded to sink to the depth of forty-four feet more, in . the same bed of clay, before another spring made its appearance. This water, which had then a pump fixed in it, was found to be more highly chalybeate than either of the former, and also to contain a much larger portion of common salt.—See Plate I.
Before we describe the process for preparing the Cheltenham salts from the waters of the saline chalybeate, as conducted at Mt. Thompson's manufactory, it will be necessary to give some account of the methods by which the products of the several springs are collected and brought to the laboratory.
Several wells having been sunk to the proper depth, at one hundred feet apart from each other, horizontal borings are then made from one to the other, and half inch leaden pipes are laid in the augur holes, until they become all connected with one main well. In this a pump is fixed, and the working cylinder is placed at a sufficient depth, to draw the water from all the collateral wells. Thus one pump is made to empty nine or ten wells.
Over each of these pumps a building ia erected, to secure it from injury; and reservoirs, capable of containing one thousand gallons each, are placed among the wella, in the most convenient situations, for receiving the water. Into these reservoirs all the water from this vast collection of wells ia driven by the several forcing pumps ; and a> these reservoirs arc placed at a sufficient elevation, they empty themselves by small uninterrupted streams into a main pipe, which is conducted under ground through the fields down to the laboratory. When it arrives there, the pipe is bent upwards, until it comes high enough to empty itself into a leaden cistern, of about twelve feet square, and which is placed in a convenient situation, for supplying the boilers, without any further labour of bucketing or pumping, but merely by opening a stop-cock, as occasion may require.
The boilers .which are employed for concentrating the waters, are very properly* made of wrought iron plates, securely put together with iron rivets. The first boiler is nine feet long, six feet in diameter, and four and a half feet deep. The second is six feet square, and four and a half feet in depth. The third is eight feet by three feet six inches, and two feet eight inches deep. These boilers are covered by plates of iron, united in the same manner; and each cover has an opening of about two and a half feet square, called a man-hole, for the purpose of cleaning out the precipitates from the boilers occasionally. Each man-hole is covered by an iron door, which moves upon strong massive hinges, and this door is screwed down, so as to make the boiler impervious to the steam which is constantly generated within. In the cover of the largest boiler an iron pipe, five inches diameter, is fixed, for the purpose of carrying off the steam; and this is conveyed underneath the laboratory to an adjoining building, for the purpose of heating the public baths. Smaller pipes are also fixed in the cover of this and the other boilers, for the collec
* We tay thete are very properly made of iron, became we know, that in some establishments utensils of copper are employed for the preparation of medicinal wits.
tion of a sufficient quantity of steam, to be employed in warming the counting-houses, the dressing-rooms at the baths, and all the other rooms belonging to the establishment. The three boilers, which are placed end to end in one continued row, are heated by one fire, wWch is plactd at one end of the largest boiler, and from this the heat is communicated to the other two in succession. When these boilers are charged with the mineral water, the fire is .lighted beneath them, and as soon as the evaporation has properly commenced, the cocks are partially opened wliich connect with the large leaden cisterns, so as to allow a small stream of the mineral water perpetually to run into the boilers, and repair the waste of fluid which the evaporation constantly occasions.
When the evaporation from the large boiler has been thus continued for seven days and nights uninterruptedly, amounting to not less than ninety-six gallons every hour, a large cock in the room beneath is opened, and the whole contents of the evaporating vessel is let off into a capacious cooler, in which a strainer is placed, for the purpose of arresting the carbonate of lime, magnesia, and the other insoluble matter which had been precipitated from the fluid, by the operation of boiling. The magnesian precipitate, which is generally very abundant, is unfit for medicinal use, in consequence of the carbonate of lime which falls with it. The proprietor, therefore, treats it with sulphuric acid, which has the property of forming a soluble salt with the magnesian earth, and an almost insoluble one with the calcareous, by which means the lime and the magnesia are separated. The magnesia having thus been again brought into a state of solution, the operator draws it off by a syphon from the precipitated sulphate of lime, and carries it to the evaporating pan, where it is concentrated and prepared for crystallization. The liquor in the second boiler, when it is thought to be sufficiently concentrated, is run off and filtered in the same manner.
When the earthy salt has had time to subside, and the filtration is completed, which generally requires twelve hours