GYMNOPYRES. 615

■ It is extreamly common in all parts of England, in the strata of blue clay usuallydug for tiles, and in this thews itself to us in a number of various shapes, sometimeshaving formed itself in the cavities of sea shells, but most frequently in the pores ofwood, pieces of branches of trees, and old boards, being found in vast abundance sa-turated with it. These, however, tho’ very common with us, I find are very rare inmany other parts of the world.

2. Gymnopyres Botryoides.

Botryoide Gymnopyris.

This is a very elegant and beautiful species; it is of a firm and hard structure, avery close and compact texture, and remarkably heavy; it is very irregular in shape andsize, but is most frequently found small and of an oblong form; it is, however,not. unfrequently met with, both of this, and of a globular shape, of many poundsin weight, and sometimes in very large irregularly shaped flat masses; it is usuallyquite naked, but sometimes its outer part rusts into a fort of ferrugineous crust ; itrequires a very smart blow to break it, and when broken, is found to be moreequally uniform and compact in its texture than any other Pyrites, being one evenmass, and resembling a body of some metal; its usual colour is a very agreeable palegreen, tho’ it sometimes varies to a very deep one, but what distinguishes it from allother Pyritæ is, that its surface is ever beautifully elevated into tubercles of varioussizes, and of irregularly roundish shapes, and sometimes not only its surface, but itswhole substance is thrown into these forms, and resembles a cluster of grapeshung thick on the bunch, or very exactly a mass of the finest botryoide Hæma-tites ; it is considerably bright where fresh broken, but less glittering than the gene-rality of these bodies.

It very freely gives sire with steel.

It will not at all ferment with Aqua Fortis, and put into the fire it burns for a littletime with a deep blue flame, cracking and bursting to pieces.

It calcines to a beautiful purple.

Examin’d by the Microscope, it appears of a very remarkably close and compacttexture. It is found in many parts of England, as in Yorkshire, Devonshire, andCornwall, but no where more plentifully than in the high cliffs of the islandof Sheppey in Kent; as it lies in the clay of the cliff, it is of a fine green, but asvast quantities of it are continually wasifd out thence and strew’d about the shore,that which is found there is usually covered with a ferrugineous coat.

PYRITÆ.

Class!. Order II. Genus I,PYRITRICHA.

Pyritæ of a simply Jlriated fruBure.

1 . Pyritrichum globosum , sup er fide irregulari.

Globose Pyritrichum , with an irregular surface .

T PIIS is the most common of all the species of the striated Pyritæ, and is

a very elegant body. ' "...

It is of a compact and firm structure, and very great weight; it is usually foundin an orbicular form, or nearly so, but sometimes is oblong, sometimes full of largeirregular tubercles on its surface, and sometimes compos’d of several orbicularmasses joined together; it is very various in size, the more frequent specimens ofit being about four or six ounces in weight, many less than an ounce, and severalof two or three pound; its surface is usually more or less irregular, and beset withtubercles, tho’ they are generally broad and depress’d, and is often variously cut in irre-