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It appears however to act in all directions: for a weight,laid upon it, either receives a like impression, or is thrownoff; and in the collections above mentioned an account isgiven of a large quantity (some ounces) which explodingfrom too great heat used in the drying of it, broke openthe doors and ssiattered the windows in pieces. Mr.Hellot found, that when a few grains of the powder wereplaced between two leaves of paper, and cemented toone of them by gum water, only the leaf which touchedthe powder was torn by the explosion, and the otherswelled out •, and that when both were brought into closecontact with it, by pressing them together, it tore themboth j from whence he concludes, that the action of theaurum is greatest on the bodies which it immediatelytouches. Both this property, and the ac u ten ess of thereport, may possibly depend upon one cause, the celerityof the expansion : experiments have ssiewn, that theresistance of the air to bodies in motion increases withthe velocity of the body in a very high ratio ; and per-haps the velocity with which aurum fulminans explodesmay be so great, that it is resisted by the air as by a solidmass.

The explosion of this preparation does not appear tomake any change in the gold. When the powder isspread exceeding thin between leaves of paper, and slowlyheated, the detonation, as Mr. Hellot observes, is slightand successive, the powder becomes purple, and appearsof the fame quality with the precipitate above mentionedwhich has no fulminating power. When a quantity ismade to explode at once, in a large vessel, or under aproper cover, for confining the particles violently di-spersed, the gold is found in fine dust, partly purplissi andpartly of its proper yellow colour : it is laid that when

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