EXPERIMENTS ON THE PLASTICITY OF ICE 
171 
Table IV. — Showing the Apparent and True relative motions of forty-five points 
two feet apart, in a line transverse to the axis of the Mer de Glace, 1844. 
Mark, 
No. 
Readings of Position. 
Apparent Motion. 
Corrected Motion. 
Remarks. 
Aug. 20 
10 A.M. 
jAug. 21 
6 P.M. 
Aug. 23 
1 P.M. 
Aug. 26, 
11 AM. 
August 
20, 21. 
August 
20—23. 
August 
20—26. 
August 
20, 21. 
August 
20—23. 
August 
20—26. 
l. 
+0-15 
-01 
-0-25 
00 
-0-25 
-0-4 
- 0-15 
-0-25 
-0-45 
-0-15 
Between 1 and 2 a slight fissure. 
2. 
+0-3 
-0-5 
-025. 
- 0-2 
-0-8 
-0-55 
- 0-5 
-0-8 
-0-6 
-0-55 
3. 
+01 5 
+015 
+0-6 
+ 0-7 
0-0 
+0-45 
+ 0-55 
-0-05 
+0-35 
+0-4 
4. 
-0-2 
-01 
+0-25 
+ 0-3 
+0-1 
+0-45 
+ 0-5 
+0-05 
+0-35 
+0-3 
5. 
-0-25 
-0-35 
-005 
+ 0-3 
-01 
+0-2 
+ 0-55 
-015 
+005 
+0-25 
6. 
-0-25 
0-0 
+0-6 
+ 1-2 
+0-25 
+0-85 
+ 1-45 
+0-2 
+0-65 
+M 
7. 
-0-2 
+0-2 
+0-9 
+ 1-8 
+0-4 
+ 1-1 
+ 2-0 
+0-3 
+0-9 
+ 1-6 
Veined structure very strong. 
8. 
00 
+0-3 
+ 1-2 
+ 2-45 
+0-3 
+ 1-2 
+ 2-45 
+0-2 
+0-95 
+2-0 
9. 
0-0 
+0-5 
+ 1-45 
+ 2-5 
+0-5 
+ 1-45 
+ 2-5 
+0-4 
+ 1-2 
+2-0 
Between 9 and 10 a fissure. 
10. 
-0-2 
+015 
+ M 
+ 2-3 
+0-35 
+ 1-3 
+ 2-5 
+0-25 
+ 1-0 
+ 1-95 
11. 
-0-4 
+0-25 
+ 1-35 
+ 2-7 
+0-65 
+ 1-75 
+ 3 - l 
+0-5 
+ 1-4 
+2-45 
12. 
-00 
+0-5 
+ 1-6 
+ 2-85 
+0-5 
+ 1-6 
+ 2-85 
+0-35 
+ 1-25 
+2-15 
13. 
-0-55 
+015 
+ 1-45 
+ 3-3 
+0-7 
+2-0 
+ 3-85 
+0-55 
+ 1-6 
+3-1 
14. 
-0-55 
+0-35 
+ l - 5 
+ 3-7 
+0-9 
+2-05 
+ 4-25 
+0-75 
+ 1-65 
+3-45 
15. 
-015 
+0-6 
+2-05 
+ 4-15 
+0-75 
+2-2 
+ 4-3 
+0-55 
+ 1-75 
+3-45 
16. 
-0-2 
+0-65 
+2-2 
+ 4-5 
+0-85 
+2-4 
+ 4-7 
+0-65 
+ 1-9 
+3-8 
17. 
-0-25 
+0-6 
+2-2 
+ 415 
+0-85 
+2-45 
+ 4-4 
+0-65 
+ 1-95 
+3-45 
18. 
-0-15 
+0-7 
+2-4 
+ 4-85 
+0-85 
+2-55 
+ 5-0 
+0-65 
+2-0 
+4-0 
19. 
-01 
+0-95 
+2-5 
+ 5-35 
+ 1-05 
+2-6 
+ 5-45 
+ 0-8 
+2-05 
+4-4 
20. 
-015 
+ 10 
+30 
+ 5-9 
+ 1-15 
+315 
+ 6-05 
+0-9 
+2-55 
+4-9 
Two fissures betw-een 19-20 and 20-21. 
21. 
+0-25 
+P7 
+3-55 
+ 6-7 
+ 1-45 
+3-3 
+ 6-45 
+ 1-2 
+2-7 
+5-25 
22. 
+01 
+1-6 
+3-5 
+ 6-7 
+ 1-5 
+3-4 
+ 6-6 
+ 1-25 
+2-75 
+5-35 
23. 
+0 3 
+ 1-7 
+40 
+ 7-55 
+ 1-4 
+3-7 
+ 7-25 
+ 11 
+3-0 
+5-95 
22-23, slight fissure very oblique. 
24. 
+0-2 
+ 1-65 
+4-0 
+ 7-9 
+ 1-45 
+3-8 
+ 7-7 
+ 1-15 
+31 
+6-35 
25. 
-03 
+ 115 
+3-5 
+ 8-0 
+ 1-45 
+3-8 
+ 8-3 
+ 115 
+3-05 
+6-9 
26. 
+0-35 
+ 1-7 
+4-3 
+ 7-95 
+ 1-35 
+3-95 
+ 7-6 
+ 1-05 
+3-2 
+6-1 
26-27, a slight fissure. It recrosses the 
27. 
+0-25 
+1-75 
+4-4 
+ 8-45 
+ 1-5 
+415 
+ 8-2 
+ 1-2 
+3-35 
+6-65 
line at 40-41. 
28. 
+0-25 
+2-05 
+4-9 
+ 91 
+ 1-8 
+4-65 
+ 8-85 
+ 1-45 
+3-8 
+ 7-25 
29. 
+0-4 
+2-2 
+5-15 
+ 9-35 
+ 1-8 
+4-75 
+ 8-95 
+ 1-45 
+3-9 
+ 7-3 
30. 
+0-15 
+ 1-9 
+4-9 
+ 9-3 
+ 1-75 
+4-75 
+ 9-15 
+ 1-4 
+3-85 
+7-45 
31. 
00 
+20 
+4-7 
+ 9 0 
+2-0 
+4-7 
+ 9-0 
+ 1-65 
+3-8 
+ 7-25 
32, 
+0-2 
+2-3 
+5-3 
+ 9-7 
+21 
+5-1 
+ 9-5 
+ 1-7 
+4-15 
+ 7-7 
33. 
+0-2 
+21 
+5-5 
+10-0 
+ 1-9 
+5-3 
+ 9-8 
+ 1-5 
+4-3 
+ 7-95 
34. 
+0-9 
+2-9 
+60 
+ 10-95 
+2-0 
+51 
+ 1005 
+ 1-6 
+4-1 
+8-15 
35. 
+0-25 
+2-2 
+5-7 
+ 10-5 
+ 1-95 
+5-45 
+ 10-25 
+ 1-55 
+4-4 
+ 8-25 
34-35, a very slight fissure. 
36. 
+01 
+2-1 
+5-5 
+10-15 
+2-0 
+5-4 
+ 1005 
+ 1-55 
+4-35 
+8-0 
37. 
-01 
+2-05 
+5-3 
+ 10-5 
+2-15 
+5-4 
+ 10-6 
+ 1'7 
+4-3 
+ 8-5 
38. 
00 
+21 
+5-9 
+ 113 
+2-1 
+5-9 
+ 11-3 
+ 1-65 
+4-75 
+915 
39. 
+0-2 
+2-4 
+6-35 
+ 11-8 
+2-2 
+6-15 
+ 11-6 
+ 1-75 
+5-0 
+9-4 
40, 
00 
+2-3 
+5-9 
+111 
+2-3 
+5-9 
+ H1 
+ 1-8 
+4-7 
+ 8-85 
41. 
+01 
+2-5 
+6-4 
+ 12-15 
+2-4 
+6-3 
+ 1205 
+ 1-9 
+5-1 
+9-7 
40-41. See 26-27. 
42. 
00 
+2-3 
+625 
+11-8 
+2-3 
+6-25 
+ 11-8 
+ 1-8 
+5-0 
+ 9-4 
43. 
-01 
+ 2-2 
+615 
+ 11-65 
+2-3 
+6-25 
+ 11-75 
+ 1-8 
+4-95 
+9-3 
44. 
00 
+2-4 
+6-5 
+ 12-35 
+2-4 
+6-5 
+12-35 
+ 1-85 
+5-2 
+9-85 
45. 
-0-2 
+2-4 
+61 
+ 12-25 
+2-6 
+6-3 
+ 12-45 
+2-05 
+4-95 
+9-9 
The results of these observations will be best understood by consulting the projected 
results in Plate IX. fig. 2, in which the advance of the marks is magnified twofold 
relatively to the spaces between them, which was necessary for the reduced scale of the 
engraving, although it has the disadvantage of increasing the deviations from sym- 
metry which might arise from errors of observation. As those who have not attempted 
the actual execution of such experiments cannot be aware of the difficulties they entail, 
it may be just to mention that during weather so unfavourable as that which occurred 
