BELEMNITES, vulgarly called thunder-bolts or
thunder-stones. They are composed of several crusts of
stone encircling each other, of a conical form, and va-
rious sizes; usually a little hollow, and somewhat trans-
parent, formed of several strize radiating from the axis
to the surface of the stone; and when burnt or rubbed
against one another, or scraped with a knife, yield an
odour like rasped horn. Their size is various, from a
quarter of an inch to eight inches; and their colour
and shape differ. They are supposed to be originally
either a part of some sea-production; or a stone formed
in the cavity of some worm-shell, which, being of a ten-
der and brittle nature, has perished, after giving its
form to the stone. They are very frequently found in
many parts of England; and the common people have a
notion, that they are always to be met with after a
storm. They are often inclosed in, or adhere to, other
stones; and are most frequent amongst gravel, or in
clay: they abound in Gloucestershire; and are found
near Dedington in Oxfordshire, where they sometimes
contain the silver marcasite. See Plate LV. fig. 10.