BOLES.

17

Sect. V. The Green BOLE.

Bolus puriffima virefcens.

Pure greenijh Bole.

r ~T"'' HIS is a perfectly fine and very beautiful Earth, considerably ponderous, of a close,

A compact, and extremely even texture, of a pale dusky greenish colour, but oftenacquiring a brown crust, and of perfectly smooth and even, but not glossy surface. Itdoes not easily break between the fingers, nor at all stain the hands; it adheres firmlyto the tongue, is readily diffusible in water, melts easily in the mouth, and is of abrackish and very disagreeable taste, without any considerable astringency, but leavesnot the least grittynefs between the teeth.

View’d thro’ the Microscope it appears of a most compact, fine and regular texture.

It makes no effervescence with Acids.

In burning it acquires a considerable hardness, and a dusky brownish red colour.Urg’d by a very violent heat it is converted into a pale green glass, with some tingeof redness.

It is found in the perpendicular fissures of strata of stone, in Yorkshire, Devonshireand Cornwal.

It has not yet been try’d in medicine, nor indeed does it seem proper for internaluse, since it manifestly owes its colour to particles of copper.

SERIES I.

Class I. Order I. Genus II.

CLAYS.

Js ARTHS firmly coherent, weighty and compadt ; fiifi\ viscid , and duSlile to a greatdegree while moifi , smooth to the touch , not easily breaking between the fingers , norreadily diffusible in water , and when mixed , not readily subsiding from it.

Sect. I. The white and whitish CLAYS.

1. Argilla albifisma ponderosa tenax. Ssuœ Parætonium Authorum.White , tough , heavy Clay. The Parætonium of authors.

This is the Parætonium Plin. L. 35. p. 684. Cæfalpin. 43. Aldrov. Musi Met. 250.Agricol. 202.

It is a very beautiful, and when pure a perfectly white Clay, very heavy, and ofa close compact, and very fine texture; when moist it is extreamly ductile, stiff,tough and viscid, and when cut, leaves a most polite and shining surface; when dryit becomes moderately hard, of a smooth and even surface, except where made irregu-lar by the extraneous bodies that are lodg’d in it; very soft and smooth to the touch,pretty easily breaking between the singers, and not at all staining the hands. It ad-heres very slightly to the tongue, and melts freely in the mouth into a substance likecream, but is generally full of accidental foulnesses that leave a grittynefs between theteeth, tho’ naturally it seems to be perfectly pure.

When examin’d by the Mifcrofcope, if a clean pure piece is chosen, it appears ofa most close, even, and regular texture, and very firm; but in the mass it discovers to thisexamination and equally to the naked eye, a strange mixture of adventitious particlesof sand, fragments of shells, Lee.

It makes a very brisk effervescence with Aqua Fortis.

It bursts and crackles in the fire, but burns to a snow white colour, with some

a itional hardness. In a very violent fire it is converted into a pure and very deepgreen glass.

This Earth was antiently found on the shores of Egypt, Cyrene, and the island ofCrete, and had its name either from a port of Egypt, near which it was gather’d, ac-

F cording