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carried on with borers of steel alone. Accurate experiments 
made and recorded at Eschweiler, and at Mannsfeld in Prussian 
Saxony, have been attended with favourable results ; and Mr. 
Rogers of the Abercarn Collieries has succeeded in proving, 
Avhilst sinking a large shaft in hard rock, the value of steel tools, 
a set of samples of which were placed in the Great Exhibition, 
and afterwards presented to this Museum. Although the suit- 
able tempering of cast steel is attended with some difficulty to 
the inexperienced, the following reasons for its preference to 
the ordinary material have been established, viz., the great 
saving in wear and tear ; the reduction of original outlay, since 
the stock of steel borers may be smaller than that ot iron in a 
lower ratio than that borne by the price of iron to steel ; the 
diminution of smith’s costs for sharpening, and of time lost by 
boring with a blunted edge, and the greater convenience of 
carriage in and out of the mine. Farther, the superior com- 
pactness of the material transmits the force of a blow more 
efficaciously to the required point, a fact corroborated by the 
observation that an iron borer will cut less ground with the same 
number of blows when new than after being for some time in use ; 
And it need hardly to be added, that in the questions of time, 
material, and cost, connected with the breaking of ground, we 
touch on some of the most important elements of economy in 
mining. 
I will not detain you with an enumeration of the points to be 
dwelt upon in the form of the excavations by which we enter 
into the earth, whether by the driving of levels or the sinking of 
shafts under different circumstances ; nor, from among the 
modes of securing them by timbering, masonry, or ironwork, 
shall I do more than bring to your notice one ingenious appli- 
cation of physical science to these purposes. It is well known 
that the sinking of a shaft through loose sand or watery rock 
often besets with great and sometimes with insurmountable ob- 
stacles the approach to the useful minerals which lie in firm 
ground below. On the banks of the Loire repeated efforts to 
reach the coal measures through a thick bed of alluvial sand 
had failed, overcome by the great influx of water and loose 
material ; when M. Triger bethought him that the simplest 
