_May 22._--The top plate over the frame No. 1 has been cracked without any particular violence or stress. It appears that it is nothing but the change of temperature that is the cause of that rupture. The accident justifies the opinion I have of cast-iron not being safe upon traction, and the precaution of having had wrought-iron bolts at the back of the frames. [_These were vertical rods which took the tensional strain._] Without these bolts what would have become of the shield, if one casting was to break? The fracture was accompanied with a loud report like that of a gun. Isambard was in the works at the time of breaking: nothing could have prevented it. [Sidenote: The shield being too much out, resolved to move it bodily.] _May 25._--I observed that nothing whatever had been gained to recover the deviation [_the shield had gradually worked 2 feet 3 inches to the westward_], which subjects us to so much inconvenience and loss of time. The only way to bring the shield right is by taking the frames sideways. _June 3._--Finding it too laborious and almost fruitless to bring the frames in the right way, I came to the determination of having them brought bodily to the east by cutting the ground on the side. I accordingly gave directions to Armstrong to proceed in making a heading out of No. 12, and by securing the side staves to continue downwards until the ground be clear. The working was accordingly discontinued in front. _June 4._--The mode of proceeding by the common way of mining shows the impracticability of carrying a large excavation anywhere, particularly under a considerable body of water. The expense of timbering would be too great, even if it could be sound. The ground above the frames is remarkably good, but under it there is a stratum of silt which breaks and falls in large masses. [Sidenote: Isambard’s service very important and most efficient.] _June 5._--Isambard got into the drift, and gave the line for the better disposition of the staves, which was afterwards done in a proper manner. Isambard’s vigilance and constant attendance were of great benefit. He is in every respect a most useful coadjutor in this undertaking. _June 10._--The last frame (No. 1) is brought close to the others, and the brickwork brought up to fill the back. [Sidenote: Dangerous state of the ground. Precautions taken.] _June 15._--On inspecting the face of the ground this morning I observed a breach in the front of Nos. 3, 4, and 5, where the ground has given way in the lower cell. This was truly alarming. I ordered iron staves to each floor in order to pin the ground, and thereby to counteract the slipping which would immediately take place.