'9'3-] ELECTRICALLY EXPLOSIVE STATE. 185 



of the building. The resuhs were tlie same when the two grounds 

 were thus independent as when the_\- were united. 



The wire to be exploded, contained within the glass tube of the 

 figure, was a quarter ampere fuse wire, having a diameter of 0.115 

 mm. A small copper wire having a diameter of 0.105 mm. was also 

 used with similar results. 



A single discharge from either the positive or the negative side 

 of the condenser caused the tube of glass to be shattered into frag- 

 ments so minute that their impact upon the face of the observer 

 when standing six or eight feet distant, produced no harmful elTect. 

 On several occasions, when the discharge came before it was ex- 

 pected, their impact upon the eyes was also harmless. 



The small glass tube shown in the figure was enclosed in a larger 

 tube having an internal diameter of about half an inch. This tube 

 was also enclosed in a strip of cardboard. In this way the dust into 

 which the inner tube was converted could be collected. It could 

 only be recognized as glass on examination with a pocket lens. 



The effect of the explosion upon the outer tube, the ends of which 

 were open, was found to be in all cases more marked when the com- 

 pression or negative discharge was sent through the wire than when 

 the discharge rods and wire were connected with the positive term- 

 inal. In some cases the rarefaction wave would produce no appar- 

 ent effect upon the outer tube, while the negative or compression 

 wave would crack it or shatter it into three or four fragments. 



In order to make comparative tests, the apparatus shown in the 

 figure was constructed in pairs, the two tubes being cut from adjoin- 

 ing parts of the same glass tube. This was also done with the larger 

 tubes which were placed between the supporting blocks and sur- 

 rounded the small tube shown in the figure. In some cases two 

 fuse wires or one fuse wire and one copper wire were placed in 

 parallel within the tube. In this way the explosive effects were 

 somewhat varied. In all cases the greater effects of the compression 

 discharge were so marked that there appears to be no doubt of the 

 result. 



In order to compare the heat effects of an ordinary direct cur- 

 rent, the wire was, by a switch connection, subjected to the current 



4 



