The oxide of arsenic has a specific gravity of 3·729, according to the experiments of Dr. Ure,—of 3·529 when opaque, according to Mr. Alfred Taylor, and 3·798, when translucent. Very incorrect notions prevail as to its taste. It was long universally believed to be acrid,[493] and is described to be so in many systematic works and express treatises; but in reality it has little or no taste at all. The reader will find some details on this point in a paper I published in the Edinburgh Medical and Surgical Journal.[494] In the present work it is sufficient to observe, that I have repeatedly made the trial, and seen it made at my request by several scientific friends, and that, after continuing the experiment as long, and extending the poison along the tongue as far back, as we thought safe, all agreed that it had scarcely any taste at all,—perhaps towards the close a very faint sweetish taste. It appears to me that the experiments made on that occasion might have set at rest the question as to the taste of arsenic, and corrected an important error long committed by systematic authors in chemistry as well as medical jurisprudence. And accordingly in this country the truth is generally known.[495] Professor Orfila, however, continues to repeat the error; for even in the last edition of his Toxicologie he says it has “a rough, not corrosive, slightly styptic taste, perceptible not for a few seconds, but persistent, and attended with salivation.”[496] These sensations must be either imaginary or the indications of an organ peculiarly constituted. It is impossible to make satisfactory experiments with safety on its impressions on the back of the palate. But we may rest assured that in general it makes no impression there at all; for it has been often swallowed unknowingly with articles of food. Not a few have in such circumstances noticed merely its grittiness, and thought there was sand in their food. Two instances only am I hitherto acquainted with, where an acrid sensation would seem really to have been experienced in the act of eating or swallowing. In one of these, noticed in Rust’s Journal, the individual who was poisoned, could not finish the poisoned dish on account of its unpleasant, very peppery taste.[497] In the other case, which was lately communicated to me by Mr. Hewson of Lincoln, the individual, who was poisoned by arsenic dissolved in his tea-kettle,—happening in the first instance to wash his mouth with the water,—observed at the time to his daughter, that it had a very odd taste; which subsequently was called a burning taste. These facts, however, are evidently not altogether satisfactory. It is not improbable that, in an _ex post facto_ description, the reporters, as others in the same circumstances have clearly done[498], confounded the subsequent inflammation with mere taste in the act of chewing or swallowing. At all events it is absolutely certain that the great majority of people who