340 
GEOLOGICAL MANirULATIONS. 
ON THE PRErAEATION OE CLA.YS, SAXDS, AND CHALK, 
EOll MICllOSCOPICAL I'UHPOSES. 
By T. llurERT Jones, Esq., E.G.S. 
To obt;iia microzoa from Gault, London, Specton, KImmcrlclge, Oxford, 
Lias, and other clays, pieces of the clay, well dried in the sunshine or 
in an oven, should be placed in a glazed pot or pipkin, and covered 
with boiliug-hot water. The clay will fall more or less completely into 
a muddy mass, which must be worked up with the water by the hands 
into a nearly uniform creamy consistence, and the thinner supernatant 
fluid then poured off. This process will be completed only by several 
repeated waterings, knoadings, and off-pourings ;. together with occa- 
sionally the drying of the undissolved portions of the clay, and again 
subjecting them to the hot-water process and repeated manipulation, 
until a small quantity only of sandy clay remains. Ihis, after having 
been dried, should be boiled in water either in a flask over a lamp or 
gas-light, or in a small saucepan on a fire for au hour or more, when, 
the muddy water having been poured awaj', the residue will be probably 
sand, fragments of shells, and numerous small foraminifera, with 
perhaps bryozoa and cntomostraca. 
Some fossiliferous deposits, such as the Eracklesham sands and clays, 
the Barton shelly clays, the Crag, the Calcaire Grossier of Paris, the 
Falunian bods of Bordeaux, &,c., fall readily into a loose state in water, 
sometimes even without much stirring. In this case, the supernatant 
water should be poured through muslin or a fine sieve, that the small 
foraminifera should not be lost. In clays, these minute shells arc 
generally filled with the matrix ; but in sandy beds they often remain 
empty, and therefore float in the water. The discoloured and muddy 
water having been repeatedly poured off from the washed sand (whether 
the sand be siliceous or calcareous, in the latter case being probably the 
detritus of shells or bryozoa), the residue should be dried, and then 
sifted into various degrees of fineness for convenience of picking. 
Fig. I. Fig. 2. Fig. 3. 
A, a, internal cylinder, with 6, b, in-turned rim ; c, perfonited zinc plate or sieve ; d, d, half of pei- 
oruted plate c ; e, e, outer cjliuder ; /,/, in-turned rim. 
It is sometimes more convenient to sift the washed materials whilst in 
the wet state, and to dry the several siftings in succession on a stove or 
in an oven. In this case, a metallic sieve, constructed so as to allow of 
the use of several moveable bottoms of perforated zinc, of different 
