had never passed from the stomach. In the winter of 1814, these distressing symptoms continued so long, and with such violence, as greatly to injure his general health, and to produce a considerable degree of emaciation, with a dry brown tongue, and a slow, weak, intermitting pulse. At that time he was restored, after some mercurial medicines, by the mistura ferri composita; but he was never long free from pain, although it was much mitigated. At the beginning of the ensuing winter, it returned with considerable violence, when the mistura ferri was again resorted to with some temporary relief. Bark and various other remedies have been given without benefit; the most immediate relief has always been obtained by large doses of magnesia and chalk in cinnamon water. The dose of these absorbents was taken in such quantities as to produce an uniform white appearance in the fæculent discharge. Reflecting on the cases which had been published, and in which the white oxide of bismuth is so strongly recommended, I determined to have recourse to it. Accordingly, about six weeks ago, he began with five grains three times a day, mixed with some tragacanth powder. Relief being obtained, the dose was increased to eight, then ten, and lastly, to twelve grains, thrice a-day, with such decidedly good effects, that P. C— called upon me yesterday, and said, he had been free from pain and uneasiness for some time, although he had occasionally, by way of experiment, indulged with impunity in such articles of food as had formerly very much disagreed, and that he had omitted taking the powders for four days, and no pain had returned. The bowels had been generally regular, but it was sometimes necessary to take a few grains of the compound of extract colocynth. Thus, this venerable gentleman has for the last three years enjoyed considerable comfort by the use of this medicine, and this relief from pain he would, most probably, not have experienced, but for the bismuth; for, during the three years which have elapsed since he first took it, the pain has at times returned, but has been uniformly removed, by having recourse to this mineral. Having experienced its good effects in this way, he has always had a packet of the white oxide by him, and, when necessary, has taken a small quantity in a tea-spoon, without weighing it, every evening for several nights. Age, and its attendant infirmities, are now, I regret to state, pressing upon him, as society will be deprived of one of its most useful and valuable members. His old grievance is occasionally troublesome with the other symptoms of declining years; and the probability is, that some organic disease exists about the stomach, most likely towards its pyloric orifice, the progress of which has been materially impeded, with always a great diminution, and occasionally a total loss, of pain for a considerable space of time. His comforts have, therefore, been greatly increased, and the approach of the infirmities of age procrastinated by the use of the bismuth. It is here worthy of remark, that the long-continued use of this medicine is productive of no bad consequences, as is the case with some remedies which produce temporary and beneficial effect, but whose continued exhibition becomes injurious to health. Care should be taken to have the white oxide of bismuth quite pure, as it is apt to be mixed with noxious ingredients in its native state before it is reduced to an oxide. Queen Street, May Fair, ART.XIV. On a new Hygrometer, which measures the Force and Weight of aqueous Vapour in the Atmosphere, and the corresponding Degree of Evaporation. By J.F.Daniell, Esq. F.R.S. and M.R.I. In the year 1812, my attention having been accidentally directed to the deposition of moisture which takes place upon certain bodies, when brought into an atmosphere which is warmer than themselves, the idea occurred to me, that the fact was connected with meteorological phenomena; and that experiments founded upon it, might be devised to elucidate the relation of air to vapour. I shortly after applied myself seriously to the inquiry, and was soon satisfied that I had not been deceived in my conjecture. The manner in which I proceeded at that time was shortly this: I made a mixture of two salts, calculated to produce cold by their solution; I then arranged half a dozen drinking-glasses upon a board, each furnished with a thermometer, and poured water into one of them. I added a tea-spoonful of the freezing mixture, which invariably produced a copious dew upon the exterior of the glass. I poured the contents of the first glass into the second, and so into the third, till the liquor, gradually acquiring heat by the process, arrived at such a temperature as no longer to produce any condensation upon the vessel. This point, as marked by the thermometer, was accurately noted, and was found to vary very considerably, according to the different states of the atmosphere. I kept a journal of the weather several months, registering the variations of the barometer, thermometer, De Luc's hygrometer, and the highest degree of the thermometer, at which moisture was condensed, and obtained some very interesting results. I afterwards varied my apparatus in the following manner: I procured five small brass hollow cylinders, three inches in diameter and four inches in height, fitted with a small cock in the bottom of each. These were very highly polished, and placed in a frame, one immediately over another, so that by turning the cock, the contents of the upper would flow into that directly beneath it. I put the cold liquid into the top bucket; and when steam was produced upon its surface, suffered the solution to run into the next, and so into the third, till all condensation ceased, when the temperature was marked as before. I found this apparatus very sensible; the bright surface of the metal being visibly obscured by the slightest film of moisture. These experiments were, however very troublesome, and required much time to ensure accuracy. The results I forbear from particularly detailing, as they are superseded by the more accurate observations which I have been enabled to make with the instrument which I am about to describe. It was not till many months after I had commenced this course of inquiry, that I discovered that the idea which had occurred to me, was not as new as I had conceived it to be. I found that Mr. Dalton, in his " Essay upon the force of steam or vapour, from water and other liquids, at different temperatures," (one of an interesting series, read before the Literary and Philosophical Society of Manchester, and published in the fifth volume of their Memoirs, which it would be difficult to match for originality, and sound philosophical induction,) thus describes his method of finding the force of the aqueous atmosphere :-" I usually take a tall cylindrical glass jar, dry on the outside, and fill it with cold spring-water fresh from the well; if dew be immediately formed on the outside, I pour the water out; let it stand awhile to increase in heat, dry the outside of the glass well with a linen cloth, and then pour the water in again: this operation is to be continued till dew ceases to be formed, and then the temperature of the water must be observed. Spring-water is generally about 50°, and will mostly answer the purpose the three hottest months of the year: in other seasons an artificial cold mixture is required." However flattered I might have been by any coincidence of opinion with so able a philosopher, the discovery of want of originality damped for a time the ardour of pursuit ; but I have ever since been impressed with the utility of any contrivance, which should enable an observer to mark with precision and expedition the constituent temperature of atmospheric vapour. Upon reading the account of the ingenious contrivance of Dr. Wollaston, which he has termed the Cryophorous, the subject again occurred to me, and I received from that instrument the hint which, after many trials, led to the completion of my hygrometer. Plate 5, fig. 1, represents the instrument in its full dimensions. A. and b. are two thin glass-balls of 11 inch diameter, connected together by a tube, having a bore of about Ith of an inch. The tube is bent at right angles over the two balls, and the arm b. c. contains a small thermometer, d. e., whose bulb, which should be of a lengthened form, descends into the ball b. This ball, having been about two-thirds filled with ether, is heated over a lamp till the fluid boils, and the vapour issues from the capillary tube f., which terminates the ball a. The vapour having expelled the air from both balls, the capillary tube f. is closed hermetically by the flame of a lamp. This process is well known to those who are accustomed to blow glass, and may be known to have succeeded, after the tube has become cool, by reversing the instrument and taking one of the balls in the hand, the heat of which will drive all the ether into the other ball, and cause it to boil rapidly. The other ball a. is now to be covered with a piece of muslin. The stand g. h. is of brass, and the transverse socket i. is made to hold the glass-tube, in the manner of a spring, allowing it to turn and be taken out with little difficulty. A small thermometer k. l. is inserted into the pillar of the stand. The manner of using the instrument is this: After having driven all the ether into the ball b. by the heat of the hand, it is to be placed in an open window, or out of doors, with the ball b. so situated as that the surface of the liquid may be upon a level with the eye. A few drops of ether are then to be poured upon the covered ball. Evaporation immediately takes place, which producing cold upon the ball a. causes a rapid and continuous condensation of the ethereal vapour in the interior of the instrument. The consequent evaporation from the included ether produces cold in the ball b., the degree of which is measured by the thermometer, d. e. This action is almost instantaneous. The thermometer begins to fall in two seconds after the ether has been dropped. A depression of 30 degrees is easily produced, and I have seen the ether boil, and the thermometer driven down below 0° of Fahrenheit's scale. The artificial cold thus produced causes a condensation of the atmospheric vapour upon the ball b., which first makes its appearance in a thin ring of dew coincident with the surface of the ether. The degree at which this takes place is to be carefully noted. A little practice may be necessary to seize the exact moment of the first deposition, but certainty is very soon acquired. It is advisable to have some dark object behind the instrument, such as a house or a tree, as the cloud is not so soon perceived against an open horizon. The depression of temperature is first produced at the surface of the liquid where evaporation takes place, and the currents which immediately ensue to restore the equiVOL. VIII. X |