X 
THE GUIDE TO NATURE 
Masses of diatoms have been heaped up in this small pocket of the Srerra Santa Ynez, in some places to 
an average depth of fourteen hundred feet. Diatoms are microscopic plants, each encased in silica. Countless 
millions of these microscopically small cases of silica, m ixed with clay and sand, are found in deposits in many 
localities including the greatest depths of the sea and the rocks of high mountain ranges. The California de- 
posits are, perhaps, the most notable in the world in ext ent and thickness, and above these diatom masses are 
patches of coarse conglomerate containing many bones of whales and sharks’ teeth. 
Diatomaceous earth is employed for many purpose s, depending somewhat on its texture and the amount of 
clay and sand intermixed with the siliceous cases. The deposits at Lampoc, California, are quarried for a ma- 
terial used as nonconducting packing for steam pipes a nd for filtering liquids. It was in a section of this deposit, 
about 350 feet below the present surface, that the herri ng shown on the opposite page were entrapped in Miocene 
times. In the layers above occur numrous fossils, but there are no such masses of them as were accumulated 
by this single catastrophe. 
