56

flowed into the lake carrying sediment with them and forming a horizontal
layer of mud lying on the first formed epsomite bed and of greater thickness
than at present. The bed of leaves (Figure 10) is evidence of the presence
of a heavier plant growth and, naturally of more rainfall, at that time ©
than at present. This involves the accumulation of a fairly large body of
water in the lake basin, both from underground and surface sources. This
water naturally contained a great deal of magnesium sulphate salts, although
in very dilute solution. A final succeeding period of aridity and desiccation
concentrated the brine until it began to crystallize at the bottom on top
of the bed of mud and sediment. Crystallization started at a great many
centres and as the crystals formed they sank into the mud. Other crystals
would form on and in circular rings around the first formed. A further
sinking would result followed by the formation of crystals in another circular
layer of a little larger radius on top of the first layer. The successive build-
ing up of the circular layers constantly increasing in diameter, would form
a.cone pointing downwards that would sink into the mud as its weight
increased and if erystallization and the consequent building up process pro-
ceeded rapidly enough the flat, upper surface of the cone would never be .
buried entirely. If a few wet seasons intervened, the cone might supposedly me
become covered by a layer of flocculent mud. More dry seasons would
cause further growth on top of the cone. It is to be presumed that if the
underlying and surrounding mud were very fine-grained some might, in
places, become mixed with the salt crystals. The cross-section of a pool
at Clinton shown in Figure 9 suggests a mode of formation similar to that
outlined above. A short season of wet weather is indicated by layer “ce”
~and general increasing aridity is indicated by the diminution of mud con-
tent from the bottom to the top. The tops of the pools are-a little lower
than the surrounding mud because their weight has caused them to sink
downward. This downward sinking of the cones, together with the
~ lateral thrust! of the growing crystals, pushes the mud to one side and causes
it to bulge upward above the pools.

EXPLOITATION.

The deposit at Clinton is owned and worked by a firm of industrial
chemists, the Stewart Calvert Company of Oroville, Washington. The
salts are excavated with pick and shovel from beneath the few inches of

= covering water, wheeled on a wooden runway to the shore, sun-dried, —
pounded with a wooden mallet, put through a 4 inch screen, and shipped
to Oroville where the more impure grades are redissolved.

Amount Avatlable.

ES The epsomite lake at Clinton (Figure 8, locality 9) covers an area of
a about 24 acres, of which it is estimated, less than one-half is floored by the
circular epsomite deposits. Though some of the pools are 4 feet thick in the
middle, 23 feet is probably the average thickness of the middle of the pools
oe near the centre of the lake. Towards the shore the pools are said to be
He shallower. Each pool is, moreover, very thin at its edges. Since the actual
a aggregate areal extent of the pools is not known and since only scanty

Jenkins states that the force of crystallization of the epsomite crystals is such that saturated solutions passing
through iron pipes split them from end to end when sudden cooling causes crystallization.