524 
Dr.  F.  Horton  on  the  Electrical 
Quartz. 
A  rectangular  slab  of  fused  quartz  was  used  in  these 
experiments.  Its  two  faces  were  ground  parallel  and  roughly 
polished,  and  the  edges  were  ground  square.  The  area  of 
the  slab  was  '946  x  '939  sq.  cm.  and  it  was  *1514  cm.  in 
thickness.  The  two  faces  through  which  the  current  was  to 
be  passed  were  platinized  by  means  of  a  colloidal  solution  of 
platinum,  and  thus  good  contact  over  the  surfaces  was  assured. 
The  platinized  slab  was  held  between  the  two  platinum 
electrodes  in  the  heating  furnace  and  its  resistance  at  various 
temperatures  measured.    The  following  values  were  obtained  : 
Temperature 
Centigrade. 
Resistancejn 
ohms. 
Conductivity  in 
mhos. 
486 
95,000,000 
1-79  xl0~9 
580 
12,000,000 
1-42  xlO"8 
652 
3,500,000 
4-86  xlO"8 
716 
1,570,000 
1-08X10"7 
703 
1,980,000 
8-59  Xl0~8 
795 
750,000 
2-27  XlO"7 
869 
409,000 
4-16xl0~7 
942 
250,000 
6-80xl0_i 
1013 
170,000 
100  Xl0~' 
1093 
121,000 
140  XlO-6 
1288 
65,200 
2-61  xlO"" 
Diagram  IX. — Showing  increase  of  conductivity  of  Quartz 
with  temperature. 
10 
9 
8 
k   7 
k  6 
k 
3 
2 
\ 
/ 
f 
> 
*   / 
n 
V)     1 
t 
i 
I 
I 
c^1 
K 
1 
A 
/ 
t 
X 
/ 
r-^ 
-er- 
500 
T£,y7P£/t#-ro/?e       C£/vT/GffAD£ . 
The'rapid  increase  of  conductivity  with  rise  of  temperature 
is  readily  seen  from  diagram  IX.,  in  which  the  above  values 
