ance. In the other patient there were fourteen calculi, under the same circumstances. Another cause of the disappearance of symptoms, and probably not of unfrequent occurrence, is the lodgment of the stone between the muscular fasciculi of the bladder, where it becomes embedded in a pouch, and occasions no further inconvenience; and in both these cases a further source of deception may arise in the stone not being readily discoverable by a sound. (See a Plate in Dr. Marcet's Essay.) Lastly, the symptoms of stone have in some few instances almost entirely vanished without any apparent cause; and in two cases that have come within my own knowledge, calculi have been found after death, the existence of which was not suspected during the life of the patient. I cannot better close these remarks, than by again insisting, both from the patient and practitioner, upon the strictest attention to the earliest stages of the disease, when, in the majority of instances, it is in a manageable state; and by urging that attention to the nature of the urinary secretions, and to the causes which modify them, upon which alone effectual preventive means can be founded; and by recalling to mind the very important aid that is to be derived from general treatment, connected with the diet, the exercise, and the mode of life of the patient. Little is known respecting the comparative prevalence of calculous disorders in different districts and countries; and, as will be seen by reference to Dr. Marcet's chapter on this subject, the means of information are very imperfect. We may, I think, rest satisfied that peculiarities in the water of different places have no influence upon the production of calculous disorders, nor does the evidence appear conclusive respecting their supposed prevalence in cider countries: upon these subjects, however, it is extremely difficult to gain unobjectionable information. It is to be hoped that the usefulness of preserving calculi, with the history of their cases annexed, will induce private individuals to contribute their specimens to some public collection, that of the College of Surgeons, for instance; where they should not merely be preserved as curiosities in a glass case, but a proper section should be made of them, and a note of their chemical composition, together with the sources whence they were obtained, annexed to each calculus. In this way, in the course of a few years, a collection would inevitably arise invaluable both to the master and pupil, and tending more than any other method to elucidate the history of calculous disorders*. Among the important facts brought to light by Dr. Wollaston's researches, is the analogy between urinary and gouty concretions, the latter consisting of uric acid in combination with soda. Another circumstance, showing the relation subsisting between gout and gravel, is the frequent alternation of the two series of symptoms, and the abundant deposition of uric sand that often announces the departure of an attack of gout. The same causes which produce gout are probably often effective, as I have elsewhere stated, in disposing to calculous affections, and the same remedies are often efficacious in both diseases. It deserves trial, how far the Colchicum Autumnale, which has proved a specific in gout, may be efficacious in preventing the formation of that excess of uric acid in the system, which, when thrown off by the kidneys, forms the commonest kind of gravel and calculus, and that which is productive of the most alarming consequences +. This plan is pursued, I understand, in the Norwich and Norfolk Infirmary, with the greatest advantage + Since writing the above, I have received a very flattering account of the success that has attended the use of the Vinum Colchici in an obstinate case of red gravel, but have not been able to obtain such particulars as can at present be published. I trust the subject will not escape the attention of those whose practice may enable them further to investigate it. I take this opportunity of referring the reader to a valuable paper of Dr. Henry on Urinary Concretions, in the tenth volume of the Medico-Chirurgical Transactions. I was not acquainted with this paper whilst writing the above, or I should have availed myself of its contents. I am happy to find many of my conclusions sanctioned by Dr. Henry's authority. ART. II. Description of a Differential Thermometer. By W. HOWARD, M.D. THIS instrument is an imitation of Mr. Leslie's differential thermometer, but is on a different principle. In his, the degree of heat is measured by the expansion of air, but in the present one by the increase of expansive force of the vapour of ether or spirit of wine in vacuo, which affords a test of great delicacy, and is easily constructed. A tube (A) being first made with a ball at each extremity, in one of which is left a small orifice, a portion of ether or spirit of wine is then introduced, and heat being applied, is brought to a state of active ebullition. At this moment the orifice is closed with a piece of wax, and finally hermetically sealed by the blowpipe. The tube may then be carefully bent in the form of a hook, and the scale and foot being adapted, the instrument is finished. (B). This thermometer is intended to be used in the same cases as that of Mr. Leslie, but I conceive it to possess some advantages. It is more delicate. When a heated body, as the hand, is approached to one of the balls, the liquid sensibly ascends or descends, and as soon as this cause is removed, begins instantly to return to its former level. Whereas in the air thermometer, the impulsion to the liquid is not instantaneous, and it continues to move in the same direction a moment after the heating cause is removed. Scale 4 Inches. If the two balls were freed entirely from air, the liquid would always remain at the same level in each branch of the tube, except a trifling difference caused by capillary attraction. This perfection cannot be obtained by the most skilful artist; there always remains behind, notwithstanding all care to prevent it, a small residuum of air, which is sufficient to make a difference in the height of the two columns. To obviate this inconvenience, before the scale is adapted, the liquid is all to be brought into one ball, and the instrument is then reversed and left for a considerable time in that position, that both balls may acquire an equal temperature, and the small portion of air may be equally diffused through them. It is then to be restored to its proper position, and the point at which the liquid finally settles, is to be marked as the commencement of the scale. The same operation is to be repeated whenever the instrument has been deranged by transportation or other causes. If it were possible to employ constantly ether or spirit of wine of exactly the same degree of strength, it is plain from the laws investigated by Mr. Dalton, that the scale would be constantly uniform; but as this is not easily obtained it is arbitrary. I have hitherto used the division of the millimetre of France *. * The best mode of constructing the above instrument, is to bend the tube previous to the introduction of the ether, a considerable portion of which should be boiled out of the tube, in order to ensure the expulsion of atmospheric air; it is also convenient to tinge the ether of a red colour, by the addition of a drop of tincture of cochineal. I have constructed upon the same principle a photometer, and an ethrioscope, both of which, though liable to some objections, are most curiously sensible to the impression of light, and to the frigorific emanations of the heavens. I have also employed a modification of the same instrument as a photometric thermometer, which I have found useful in comparative experiments upon the light of different flames. For this purpose, the instrument is constructed as shewn in the above wood-cut, by Dr. Howard; the upper ball is then covered by a thin coating of Indian ink, and the other with gold leaf, applied by a dilute spirit-varnish; it is then covered by a thin glass shade. Upon bringing a candle near the black, or sentient, ball, that is within the distance of 14 inches, or one foot, it produces an instantaneous depression of the column of liquid. Placing this instrument at the distance of 16 inches from the flame of a wax candle, it fell 1o in l'. A gas flame which I had previously ascertained, by a comparison of shadows, to give the light of eight wax candles, caused a depression of 10o in 1', when placed at the same distance from the instrument. W. T. B. ART. III. Select Orchidea from the Cape of Good Hope.. Continued from page 44 of Vol. VI. Of SATYRIUM bracteatum, PTERYGODIUM alatum, CORYCIUM orobanchoides. NOTE. Vol. 6. p. 44. 1. 17. for " DISPERIS," read "DISA." Plate III. Fig. 1. SATYRIUM BRACTEATUM. SATYRIUM. Corolla ringent; petals five front-ones connate at the base. Label at the back of the corolla, vaulted, with a double spur or a double pouch at the base. Anther reversed. Stigma two-lipped. Oвs. a genus remarkable among its nearer co-ordinates for having the true labet at the back of the flower; for Swartz, as Mr. Brown has shewn, in his Prodromus of the Flora of New Holland, was wrong in supposing the middle front petal to be the label in this genus. SATYRIUM bracteatum, leaves ovate, three-nerved, bractea ovate, reflexed, spurs very short and obtuse. Satyrium bracteatum. Thunb. Prod. 6. Flor. Cap. 1. 93. Swartz in Act. Holm. 1800. 216. Idem in Schräder's Neues Jour nal, 1. 35. Willdenow Sp. Pl. 4. 56. Ophrys bracteata. Linn. Suppl. 403. Root with roundish tubers. Stem about a span high. Radical leaves ovate, nerved; stem ones ovately oblong, several. Spike many-flowered, close; bractes ovate, spreading, longer than the flowers. Label roundish. Lower lip of the corolla, 3-lobed. Plate III. Fig. 2. PTERYGODIUM ALATUM. PTERYGODIUM alatum; stem leafy, leaves lanceolate, label three-cleft, middle segment very short. Pterygodium alatum. Swartz in Act. Holm. Idem in Schräder's Neues Journal, v. 1. 37. 1800. p. 218. Ophrys alata. Thunb. Prod. 2. Linn. Suppl. 404. Willd. Sp. Pl. |