668 ME. MALLET ON THE TEANSIT ^TELOCITY OF EAETHQHAEY: WAVES. 
Table X. — Holyhead-Rock Compression. Quartz Rock. — Results of Compression 
compared. Column of unit length =1 inch. 
i 
Pressure in 
C. 
D. 
Gr. 
H. 
No. of 
pounds on unit 
Hard quartz 
Hard quartz 
Soft quartz 
Soft quartz 
experiment. 
of siu’face 
across 
with the 
across 
with the 
= 1 square inch. 
lamina. 
lamina. 
lamina. 
lamina. 
lbs. 
in. 
in. 
in. 
in. 
1. 
50 
•0000 
•0000 
•0000 
•0000 
2. 
1,000 
•0039 
•0374 
3. 
2,000 
•0992 
4. 
3,000 
•0043 
•0993 
5. 
4,000 
•1007 
6. 
5,000 
•0052 
•1021 
7. 
6,000 
•1036 
8. 
7,000 
•0101 
•1741 
9. 
8,000 
•0065 
Crushed. 
10 . 
9,000 
•0078 
11. 
10,000 
•0115 
12 . 
11,000 
•0078 
•0129 
13. 
12,000 
•0176 
14. 
13,000 
•0104 
•0359 
15. 
14,000 
•0117 
Crushed. 
16 . 
15,000 
•0130 
17. 
16,000 
•0091 
•0169 
18. 
17,000 
•0182 
19. 
18,000 
20. 
19,000 
•0104 
•0208 
21. 
20,000 
•0117 
Crushed. 
22. 
21,000 
•0156 
23. 
22,000 
24. 
23,000 
25. 
24,000 
26 . 
25,000 
27. 
26,000 
•0221 
28. 
27,000 
29. 
28,000 
30. 
29,000 
31. 
30,000 
32. 
31,000 
33. 
32,000 
•0234 
34. 
33,000 
35. 
34,000 
•0247 
36. 
35,000 
37. 
36,000 
•0260 
38. 
37,000 
Crushed. 
in. 
in. 
in. 
in. 
Mean compression for each J 
1000 lbs. on unit of surface. | 
•0007085 
up to 
35,000 lbs. 
•0010947 
up to 
19,000 lbs. 
•0014666 
up to 
12,000 lbs. 
•0172666 
up to 
6000 lbs. 
An examination of these Tables presents some remarkable and, so far as I am aware, 
now for the first time observed results. 
As might have been expected, the qiiartz-rock is much less compressible generally 
than the slate-rock, with this exception, however, that the softest specimens of quartz- 
rock, and those alone, are much more compressible than the softest slate, when both 
are compressed in the direction of or parallel to the lamination. 
