412 Proceedings of the Royal Physical Society. 
gold-field, numerous veins and reefs of quartz are found ; 
and in sinking a shaft, if tliey know accurately the posi- 
tion of the gutter, which they can find by boring at in- 
tervals all round, they sink, if the extent of their claim 
permits them to do so, away from the lead or gutter, 
and by this means perhaps avoid one thickness of rock, 
and then they drive for the gutter. I will try to illustrate 
my meaning by a rough sketch (fig 2). The lowest part of 
Fig, 2. — Diagram to illustrate the varying rock strata cut through by dif- 
ferent mining companies. It represents at the top, the natural 
surface and soil; below this the dotted bed represents the 1st 
rock come to, next the shaded bed represents a bed of clay, then 
another bed the 2d rock, next a bed of clay, below it the 3d 
rock, next a bed of drift, and below it the 4th rock, under which 
lies the gutter; the lowest shaded portion forming the floor of 
the whole, being the slaty reef, as it is termed — the original sur- 
face of the country. 
the diagram, marked A, is the gutter containing wash dirt. 
These gutters are old water-courses which at one time 
existed on this continent, and they have worn themselves 
down in the soft slaty reef which was then the earth's 
surface. 
" This reef sometimes crops out to the surface on this gold- 
field, and at other times, as represented by my diagram, 
has been worn down by old world floods till it is only 
reached between 350 and 400 feet in the bottoms of these 
gutters. By sinking a shaft at B, the company would 
