46 T. 0. Mendenhall— Edison's Tasimeter 



pressure was prolonged to twenty-four hours, the ] 

 the end being slightly lower than at any previous reading. 

 Finally, the apparatus was left with the weight applied for one 

 week. No measurements were made during that time, but at 

 the end the resistance was found to be decidedly lower than it 

 was at the end of two hours after the application of the pressure, 

 and it is especially to be noticed that on the removal of the 

 pressure the normal resistance of a week before was instantly 

 recovered. In this case the pressure applied was 100 grams. 

 The resistance before the application of the pressure was 11*08 

 ohms. Upon applying the pressure it immediately fell to 2'34 

 ohms. In two hours this had been reduced to 210 ohms, and 

 at the end of a week it was 1.93 ohms. Thus in two hours it 

 was reduced by about ten per cent, and after one week it was 

 again about ten per cent lower. 



It appears, therefore, that the element of time plays an impor- 

 feant part in the phenomena exhi on disk, and 



it seems highly probable that this has been one of the principal 

 causes, if not the chief cause, contributing to the inconstancy 

 and unreliability of the indications of the Tasimeter. The 

 experiments made thus far indicate a fair degree of constancy 

 in its results when this factor is considered. The writer hopes 

 to be able to make further examination concerning the extent 

 to which all of the conditions necessary to its use may be 

 controlled. 



The resistance of carbon under pressure has been made the 



usion reached by 

 really due to the 

 contact between the electrodes, and it appears that Professor 

 W. F. Barrett has arrived at a similar conclusion, as a result of 

 experiments made upon a "button of compressed lamp-black." 

 Without knowing anything about the nature of these experi- 

 ments, the w i iter .h-n. ,. t'« ovord his b.-iiel thai this theory 

 does not entirely account for the facts stated above. Besides, 

 it seems a little difficult to understand how so small a pressure 

 as lifty grams added to an already existing pressure of about 

 !,-.unt e;m increase the area of contact between a flat 

 plate and a flat disk nearly four times, to say nothing of the 

 -'recovery" which takes place so promptly upon the removal 

 of the pressure. 



