q 
Mining for Metallic Minerals, whether in the primitive or secondary for- 
mation, is of a much more uncertain and speculative character than that for 
Coal. In the Coal Measures, we can ascertain at a moderate expense, by 
boring, whether seams of Coal exist; and if existing, their thickness, This 
being learnt, an approximate estimate of the quantity of saleable Coal in a 
given area, and the cost of its get, is no difficult matter. 
With the Rake and Pipe Veins of the Lead Fields, the case is different. 
A vein which generally approaches the perpendicular, rather than otherwise, 
presents little chance of being probed by boring; and even should it be 
pierced, the mineral capable of extraction through a borehole would afford 
very unsafe data by which to judge the value of the vein. ‘The hole might 
quite possibly pass through the only portion of ore contained within many 
fathoms ; or, with an equal possibility, penetrate the poor part of a vein, 
which at any other point would have yielded widely different data. 
Mineral veins may be, and frequently are, discovered (in places where the 
surface of the rock is to be seen) by the fracture and interruption in the 
regularity of the strata. 
In all Mining districts, but especially in a stratified country, the pheno- 
mena presented by veins, their frequent heaves and dislocations, and their 
varied appearances when bounded by different rocks, call for very close 
attention; and even a dependence upon knowledge acquired in one district, 
may prove fatal in another. 
The Miner should be perfectly acquainted with the nature of those sub- 
stances, which it is his daily task to seek in the bowels of the earth,—as 
well as with those which, though perhaps worthless in themselves, generally 
indicate the presence or absence of the immediate objects of his search. 
Long and practical experience, combined with a knowledge of Geology 
and Mineralogy, can alone furnish him with this requisition; and is there- 
fore essential to success. 
174 REPORT—1858. 
On the Collapse of Glass Globes and Cylinders. 
By W. Farrpairn, F.R.S. 
At the Meeting of the British Association last year, a paper was read upon 
the Collapse of Cylindrical Wrought-iron Riveted Tubes by a uniform 
external force. These experiments upon a ductile and fibrous material, led 
to some novel and important results, and suggested the propriety of similarly 
testing the resisting powers of a perfectly homogeneous crystalline and 
rigid material, in order that our knowledge of the laws which govern the 
resistance of vessels to collapse, might be confirmed and extended. 
For this purpose, glass was the material selected, not only on account of 
its fulfilling better than almost any other material the conditions sought for, 
and from the ease with which it could be manufactured into the required 
forms ; but also because it was hoped that the results would be practically of 
value in those cases in the arts and in experimental science in which it is so 
extensively employed. 
The experiments were conducted in a similar manner te those upon iron. 
Some glass cylinders and globes were procured direct from the glass-house, 
blown out of good flint-glass. ‘The open ends of these were then hermetically 
sealed by the blow-pipe, and they were placed in a strong wrought-iron vessel, 
capable of sustaining a pressure of 2500lbs. per square inch. Water was 
then pumped in by means of a force-pump, and the pressure was recorded 
