SCIENCE IN RELATION TO THE ARTS. 221 



with powders of usual composition and with others in which the pro- 

 portion of sulphur was considerably increased, the extent of erosive 

 action of the products escaping from the explosion-vessel under high 

 tension being carefully determined. With small charges a particular 

 powder containing no sulphur was found to exert very little erosive 

 action as compared with ordinary cannon-powder ; but another pow- 

 der, containing the maximum proportion of sulphur tried (15 per cent), 

 was found equal to it under these conditions, and exerted very decid- 

 edly less erosive action than it, when larger charges were reached. 

 Other important contributions to our knowledge of the action of fired 

 gunpowder in guns, as well as decided improvements in the gunpow- 

 der manufactured for the very heavy ordnance of the present day, 

 may be expected to result from a continuance of these investigations. 

 Professor Carl Himly, of Kiel, having been engaged upon investiga- 

 tions of a similar nature, has lately proposed a gunpowder in which 

 hydrocarbons precipitated from solution in naphtha take the place of 

 the charcoal and sulphur of ordinary powder. This powder has among 

 others the peculiar property of completely resisting the action of wa- 

 ter, so that the old caution, " Keep your powder dry," may hereafter 

 be unnecessary. 



The extraordinary difference of condition, before and after its ig- 

 nition, of such matter as constitutes an explosive agent leads us up to 

 a consideration of the aggregate state of matter under other circum- 

 stances. As early as 1776, Alexander Volta observed that the volume 

 of glass was changed under the influence of electrification, by what he 

 termed electrical pressure. Dr. Kerr, Govi, and others have followed 

 up the same inquiry, which is at present continued chiefly by Dr. 

 George Quincke, of Heidelberg, who finds that temperature, as well as 

 chemical constitution of the dielectric under examination, exercises a 

 determining influence upon the amount and character of the change 

 of volume effected by electrification ; that the change of volume may 

 under certain circumstances be effected instantaneously as in flint- 

 glass, or only slowly as in crown-glass, and that the elastic limit of 

 both is diminished by electrification, whereas in the case of mica and 

 of gutta-percha an increase of elasticity takes place. 



Still greater strides are being made at the present time toward a 

 clearer perception of the condition of matter when particles are left 

 some liberty to obey individually the forces brought to bear upon 

 them. By the discharge of high-tension electricity through tubes con- 

 taining highly rarefied gases (Geissler's tubes), phenomena of dis- 

 charge were produced which were at once most striking and suggestive. 

 The Sprengel pump afforded a means of pushing the exhaustion to 

 limits which had formerly been scarcely reached by the imagination. 

 At each step the condition of attenuated matter revealed varying prop- 

 erties when acted upon by electrical discharge and magnetic force. 



