508  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
Tensile  strength  of  standard  briquettes   (7  sq.  in.  section). 
No.  of  bri- 
quette. 
Composition. 
Water. 
Time. 
Total. 
Date  made. 
Date  tested. 
Strength. 
In  wa- 
ter. 
In  air. 
1 
Bri- 
quettes. 
Aver- 
age. 
20, 580 
1 
o 
Neat 
Perct.     Hrs. 
24       24 
Days. 
Days. 
«24 
May    26 
May    27 
f       225 
250 
1       240 
238 
20, 590 
Neat 
24 
24 
6 
J 
May    26 
July     2 
I"       485 
j       495 
[       500 
490 
20, 595 
6 
\\  cement,  3 
)     sand. 
\n 
24 
6 
7 
May    26 
Jnly      2 
j       340 
I       320 
j-     330 
20,590a 
la 
2a 
3a 
4a 
Neat 
24 
24 
27 
28 
May    26 
June  23 
635 
647 
621 
652 
638 
■    638 
20,  595a 
6a 
7a 
8a 
9a 
1  cement,  3 
sand. 
}  13 
24 
27 
28 
May    26 
June  23 
425 
432 
430 
435 
427 
.    430 
"  Hours. 
As  is  usually  the  case,  the  shales  to  be  used  at  Independence  and 
Neodesha  are  more  variable  in  nature  than  the  limestones.  In 
places  they  change  rapidly  in  character,  principally  by  a  variation 
in  the  amount  of  sand  present.  The  amount  of  calcium  carbonate 
also  is  exceedingly  variable,  ranging  from  almost  20  per  cent  down  to 
a  very  small  amount;  but  with  these  variations  the  proportions  of 
magnesia  and  of  the  alkalies  remain  fairly  constant,  and  in  no  case 
lias  an  excessive  amount  of  magnesium  carbonate  been  found.  The 
following  is  an  analysis"  of  the  shale  underlying  the  limestone  at 
Neodesha  : 
"  Univ.  Geol.  Survey  Kansas,  Annual  Bull,  on  Mineral  Resources.  1902,  p.  50. 
