A substance of a sparry appearance found in mines, called cauk or calk, has by the later chemists been discovered to contain an earth, the properties of which entitle it to form a new genus among earthy bodies. From its remarkable specific gravity, it has obtained the name of terra ponderosa, or barytes; and is now found to exist in various combinations, particularly, united with the vitriolic, and with the aerial acids. It was from the first suspected to be of a metallic nature by that eminent chemist Pro-fessor Bergman; and Dr. Withering, in some excellent observations and experiments on it published in the Philos. Transaactions (vol. Ixxiv. part ii.) places it between the earths and the metallic calces. Its native combinations exert deleterious effects upon animals; and its artificial ones, though milder, are capable of acting with violence in moderate quantities; a farther presumption of its metallic nature, since no combinations of the simple earths shew any activity of that kind. From the aerated barytes an artificial combination has been made with the muriatic acid, which has been introduced into medicine.

Dr. Crawford, in the year 1789, made several trials in St. Thomas's hospital of the muriated barytes, the result of which was published in the Medical Communications, vol. ii. The preparation he used was a saturated solution of the salt in water; but in part of the cases this salt was not the pure muriated barytes, but had a mixture of an eighth of muriated iron; the medical effects, however, of the pure and the compound salt were not found to be sensibly different. The cases in which it was used with the moil striking success were scrofula in its different forms and combinations, with swelled glands, foul ulcers, enlarged joints, and general cachexy. Some of these which had refilled the usual remedies, were Angularly relieved by the muriated barytes, either given alone, or in conjunction with mercurial and antimonial medicines and bark. The dose varied from two drops to twenty, twice a day; few patients, however, could bear more than from six to ten without nausea; and it did not appear that by habit the stomach was enabled to bear a considerable increase of dose, but rather the contrary. In a few instances this medicine appeared to increase the cuticular se-cretion; in most it occasioned an unusual flow of urine: and almost universally improved the appetite and general health. Sometimes it produced vertigo, an effect apparently connected with its nauseating quality. It is not to be doubted, Dr. Crawford observes, that if admi-nistered injudiciously, it is capable of producing deleterious effects, both by disordering the nervous system, and bringing on violent vomiting and purging. From trials made upon dogs, it appears that a very large dose would prove fatal.

It may be proper to mention, that the aerated barytes is found in the lead mine of Anglezark, near Chorley in Lancasthire, and as far as appears, there only in England. [See a paper by Mr. James Watt, junior, in the third volume of the Manchester Society's Memoirs.]