Mica^ Ehonite and Gutta-percha. 165 



Surface resistance of quartz {crystal). —The distance from 

 terminal to terminal was 1-5^™ ; the actual figures were: 

 76,000,000 O Feb. 20th Hyg. 17° 

 75,000,000 " " 27th " 34° 



Calculating the mean for one surface of one square centi- 

 meter, we have 521,000,000 11. 



Surface resistance of ebonite. — Two strips were used ; the 

 breadth of gaps was in one case o'5™™, in the other 6*2™°^. 



Calculating the resistances actually obtained, for one surface 

 of one square centimeter we have 



No. 1 1,107,000,000 O Hyg. 34° 

 " 2 2,940,000,000 " " " 



2,000,000,000 " 

 These results are sufiiciently discordant ; those with quartz are 

 scant, but damp weather prevented additional observations. 



In closing this article, I give two determinations of the 

 resistances employed in the investigation, for the purpose of 

 showing the degree of accuracy readily obtainable in the 

 process of building up high units by my method. The two 

 operations were separated by an interval of about a week ; the 

 units were one year old. 



53,760 



53,830 O 



71,860 



72,370 " 



81,400 



80,500 " 



244,000 



211,000 " 



220,000 



205,000 " 



297,000 



292,000 " 



389,000 



384,000 " 



1,161,000 



1,163,000 " 



585,000 



554,000 " 



1,565,000 



1,504,000 " 



1,401,000 



1,380,000 " 



2,246,000 



2,193,000 " 



2,891,000 



3,140,000 " 



2,203,000 



2,193,000 '' 



3,707,000 



3,432,000 " 



2,990,000 



3,130,000 " 



3,070,000 



3,130,000 " 



1,958,000 



1,803,000 " 



7,808,000 



8,194,000 " 



7,902,000 



8,460,000 " 



8,720,000 



8,540,000 " 



5,584,000 



5,560,000 " 



8,120,000 



8,194,000 " 



6,780,000 



6,906,000 " 



New York, June 1st, 1902. 





