268 &. Mallet—Temperature attainable by Rock-crushing. 
steel, heated to a brilliant yellow heat, is passed between the 
rolls of the iron mill, and the massive lump is rapidly elongated 
into a bar, its temperature, notwithstanding that it is rapidly 
and constantly losing heat by radiation and evection, is observed 
visibly to increase, so that the mass becomes at a certain stage 
white or welding hot by the transformation into heat of the 
work of deformation so rapidly and powerfully applied to it. 
The action of the machine employed in the arsenal at Wool- 
wich for making lead rods to be afterward pressed into bullets 
affords another striking example. In this machine a cylindric 
block of lead, maintained at a temperature of 400° Fahr., is by 
a steady pressure upon the end, which is 8’"5 in diameter, of 
16,700 lbs. per square inch of its surface, forced through an 
aperture at the other extremity into a rod of 0525 diameter, 
at such a rate that five inches in length of the cylindric block 
becomes a rod of about 100 feet in length of the above diame- 
ter per minute. We have thus 393,906 foot-pounds of work 
done upon the lead per minute, dividing which by J we have 
5102 British units of heat developed per minute from the 
transformed work. In the actual machine the whole of this is 
into the original block of 8’5x5", we should find 
the lead in the latter not only liquid, but considerably above 
its temperatue of fusion, or at nearly 700° Fahr. It is obvious, 
The preceding remarks appear to the writer sufficient to 
show that there is no physical difficulty in the conception 1n- 
pe 
crushing the materials of our earth’s crust are sufficient locally 
to bring these into fusion. 
