34 
feet long, but to this any number of similar tubes may be 
firmly welded; above this are the long bollow boring rods, the 
whole being set in motion and made to revolve on its axis by 
suitable machinery driven by steam; the rock as it is cut rises in 
the form of round solid pillars in the cylinder, when full it is 
drawn up to the surface and the cores extracted, sometimes in 
lengths of six feet, at others in broken fragments. At the Sub- 
Wealden Exploration at Netherfield, near Battle, in Sussex, 
the crown revolved from 150 turns a minute in soft strata to 
300 in hard rock. Water is pumped down the centre and rising 
at the sides conveys the debris in suspension to the surface. 
The so-called Diamonds in the Bock Drill are in reality a 
mineral found in Brazil, and called by the Miners “ Carbonado 
when first offered for sale the price was fourpence a carat, now 
it is from 15 to 20 shillings ; it is not brilliant and has no 
cleavage planes. Among English Diamond Merchants this 
substance is known as and called “ Carbonate.” 
These pieces of Carbonate being firmly set in a crown, form a 
drill, which when driven by steam will pierce the hardest rocks : 
the wear of the Carbonate is so small that in boring quartz to a 
depth of 30 feet not more than one sixty-fourth of an inch 
would be worn off. 
The conditions necessary for carrying out successfully the 
borings for an artesian well are the following : The existence of 
a mass of permeable stratum or material, enclosed, except at its 
outcrop, by two layers of impermeable strata. The lowest point 
on the exposed surface of the porous matter through which the 
water filters should be above the level of the point where the 
well is proposed to be sunk. The mass or cubical capacity 
for water of the permeable stratum should be sufficient to meet 
the demands upon it, and there must be continuity of the 
permeable bed for the uninterrupted passage of water, and 
no flaw or break in either of the confining layers by which 
the water might escape; and this is a frequent source of 
failure; sometimes in deepening the bore instead of increas¬ 
ing the flow it ceases altogether, the water escaping through 
another outlet, and the existence of one spring is no guarantee 
that another will be found at the same depth in the neighbour- 
