The degree of rapidity with which an explosive substance undergoes metamorphosis, as also the nature and results of such change, are in the greater number of instances susceptible of several modifications, by variation of the circumstances under which the conditions essential to chemical change are fulfilled. Excellent illustrations of the modes by which such modifications may be brought about are furnished by gun-cotton, which may be made to burn very slowly and almost without flame, to inflame with great rapidity, but without development of great explosive force, or to exercise a violent destructive action; according as the mode of applying heat, the circumstances attending its application, and the mechanical conditions of the explosive agent are modified. Nitro-Glycerin or Glonoin, which bears some resemblance to chloride of nitrogen in the suddenness of its explosion, requires the fulfillment of special conditions for the full development of its explosive force. Its explosion by the simple action of heat can be accomplished only when the source of heat is applied for a considerable time in such a way that chemical decomposition is established in some portion of the mass, and is favored by the continued application of heat to that part; under these circumstances the chemical change proceeds with very rapidly accelerating violence, and eventually brings about a sudden transformation of the heated portion into gaseous products, which transformation is instantly communicated throughout the mass of Nitro-Glycerin, so that confinement of the substance is not necessary to develop its full explosive force. This result can be obtained more expeditiously, and with greater certainty, by exposing the substance to the concussive action of a detonation produced by the ignition of a small quantity of fulminating powder placed in contact with or near to the Nitro-Glycerin. The development of the violent explosive action of Nitro-Glycerin, freely exposed to air, through the agency of a detonation, was regarded until recently as a peculiarity of that substance; but Abel’s experiments have shown that gun-cotton and other explosive compounds and mixtures do not necessarily require confinement for the full development of their explosive force; this result being obtained (and very readily in some instances, especially in that of gun-cotton) by means similar to those applied in the case of Nitro-Glycerin, viz.: by the percussive action of a detonation.