THE LITHOFEACTEUB. 
149 
notable in its application in wet rocks and under water, as well 
as in the far less amount of danger incurred in transport from 
place to place, and in charging the blasting-holes. Litho- 
fracteur possesses this advantage amongst others over dynamite, 
that it can be exploded at a lower temperature, and it is stated 
that it can be fired by an energetic detonator even at the 
temperature of — 12°*5 Centigrade, whilst dynamite ceases to 
explode at + 5° to 6° Centigrade. 
For mining purposes the great desideratum is the quantity 
and nature of the work done by the explosive, for the main 
expense in such work is the cost of boring holes for the charges. 
If, then, these can be diminished in number as well as in 
dimensions by the greater power of the blasting material, the 
saving in the quarrying or mining operation becomes far more 
important than the difference in cost between the cheaper and 
less effective blasting powder and the nitro-glycerine com- 
pounds, although that difference in price may be considerable 
pound for pound. One may generally assume, according to the 
statistics so far attainable, that 1 lb. of lithofracteur acts as 
powerfully as from 6 lbs. to 7 lbs. of blasting powder; but no exact 
comparisons have yet been made, and indeed no means have 
been as yet found for absolute accuracy in such determinations. 
The difference in the price of the powder is also more than 
equalled in the saving of human labour in drilling the holes ; 
and it is generally assumed that this gain alone deducts a third 
from the expense which the manual labour required for blasting 
powder entails. For the economical working with lithofracteur 
or dynamite, the holes should be neither too wide nor too 
deep ; in most cases it is not required to exceed from 36 in. 
to 40 in. in depth, while for breadth \\ in. at most is suffi- 
cient. The harder and stronger the rock the wider must the 
hole be. One of the great values of lithofracteur is its power 
of blasting into perfectly fiat faces, vertical or horizontal. 
This was admirably illustrated in the first experiments made 
in this country at the quarries of Mr. France, at Nantmaur 
and the Breidden, in May last year. One instance of absolutely 
horizontal boring into the fair face of the dense limestone 
quarry cliff at the former place, and one example of perfectly 
vertical boring into a floor of a tough homogeneous greenstone 
rock at the latter, jutting out at right angles from the towering 
cliff face of the latter noble hill 1,200 ft. and over in unbroken 
height, will suffice to show the really useful as well as powerful 
energy which this explosive is able to exert in the commercial 
work of quarrying. In the experiment at Nantmaur, three holes 
were drilled as absolutely horizontal as human hands could drive 
them into a bed of solid rock 10 ft. above the quarry floor, and 
forming a continuous part of the lower portion of the cliff 150 ft. 
