238 Intelligence and Miscellaneous Articles. 
shown to be much faulted and brought up against Upper Ludlow 
shales and Aymestry rocks. The Wenlock shales and the Wenlock 
limestone are then traversed; these are much faulted, the Lower 
Ludlow beds again coming in, followed by Aymestry rock, Upper 
Ludlow shales, Downton sandstone, and, at the east end of the 
tunnel, by red and mottled marls, grey shales and grits, purple 
shales and sandstones, with the Auchenaspis-beds, forming the pas- 
sage-beds into the Old Red Sandstone, as described in a former 
paper (Quart. Journ. Geol. Soc. vol. xvi. p. 193). 
In a note, Mr. J. W. Salter, F.G.S., described the great abun- 
dance of Upper Silurian fossils found in these cuttings, and now 
chiefly in the collection of Dr. Grindrod and other geologists at 
Malvern and the neighbourhood. 
XXXVI. Intelligence and Miscellaneous Articles. 
ON THE FIBROUS ARRANGEMENT OF IRON AND GLASS TUBES, 
[Extract from a Letter from Dr. Debus to Professor Tyndall. ] 
Queenwood College, Feb. 17, 1861. 
FEW weeksago Mr. E. brought me a piece of iron tube which 
had been exposed for several years to the action of moist air. 
Nearly the whole of the tube was converted into oxide ofiron. This 
suggested certain thoughts, the results of which were new and in- 
teresting to me. 
You know, when a piece of glass tube, sealed and filled with water, 
is heated, the tube is cracked, and cracked in a longitudinal direc- 
tion. Why is this? Glass tubes are made by taking a piece of hol- 
low glass in a viscous state and pulling it at both ends. Now, the 
particles of the glass do not adhere to each other on all sides 
with a force of the same strength, but in some directions this force 
is stronger, in others weaker. Under the strain produced by the 
pulling, they arrange themselves so as to offer to the pulling force 
the greatest resistance. Therefore the greatest cohesion of the par- 
ticles is found, in the formed tube, parallel to the length of the tube, 
and the weakest cohesion in a direction perpendicular to this. This 
explains the cracking of the tube as mentioned above. 
Mr. E. could not give me exact information as to how iron tubes 
are made, but he said they were passed through rollers. Now, if 
this is correct, the particles of iron ought to arrange themselves in 
a similar way to the particles in a glass tube. If such a tube oxi- 
dizes, the oxygen naturally would overcome the cohesion of the iron 
first in those places where this cohesion is weakest, that is, in lines 
parallel with the tube. Such is actually the case. The tube men- 
tioned had deep furrows, so to say, hollowed out by the oxygen along 
its length, just in the same way as u glass tube would crack under 
pressure. 
I need not mention to you other examples; but one case more, 
and then I have done. You gave some years ago an explanation of 
