210 



HENKY A. ROWLAND 



TABLE II. 



MAT 1. RELATIVE EFFECTS FOR DIFFERENT INTENSITIES OF CHARGE AND 

 TIME OF CONTACT 



These Tables seem to prove beyond question that calcite in clear 

 crystal has no electric absorption. Quartz seems to have about ^ that of 

 glass; but we have remarked that quartz is not a good substance to test 

 the theory upon. 



Some experiments were made with cleavage-plates of selenite, which 

 are always more or less imperfect, as the laminae are very apt to sepa- 

 rate. These gave, however, effects about -J or ^ those of glass. 



In order to test still further the absence of electric absorption in 

 calcite, the electrometer was rendered very sensitive, and the calcite 

 plates were tested with gradually increasing charges, from that which 

 in glass gave 200 millim. after 1 second contact, up to the maximum 

 charge (ten sparks of the unit-jar) which the condensers were capable 

 of carrying. In these trials, the calcite still showed no effect, even 

 with 30 seconds contact. During these experiments glass was fre- 

 quently substituted for the calcite, to leave no question but that the 

 apparatus was in working order. 



It is to be noted that the relative effects of the quartz and the glass 

 were different for dried plates and plates exposed to the atmosphere. 

 This was possibly due to the glass being a better insulator, and thus 

 retaining its charge better when dry than in its ordinary condition. 



IV 



Thus we have found, for the first time, a solid which has no electric 

 absorption; and it is a body which, above all others, the theory of 

 Clausius and Maxwell would indicate. The small amount of the effect 



