G E A Y &

cording to some; or as others rather think, from the name of a town in that kingdomwhere it was usually fold. Pliny affirms its having its name from Egypt; and Vitru-vius will have it to be from tire Port which lay against 'Cyrene; and Volaterranusfrom a city of that name. It is at present common on the th ores of most of theislands of the Archipelago, tho’ not observed or regarded. It is found in masses of dif-ferent sizes, generally as soft as the softer Clays, while in the strata; and by rollingabout on the beech in this state, it gathers up sand, small shells, and other extraneousbodies, of vvhich it is always full, and to the sea water it thus imbibes, it certainly owesthe fastness of its taste, which I therefore avoided mentioning in the description, asmost probably an accident, and no inherent property in the body.

The ancients, and some authors since their time, have had many different opinionsin regard to the origin of this substance: Pliny imagin’d it the froth of the sea, coalescedinto a solid mass, with the addition of some mud; and mentions this as the generalopinion of his time, Spumam mark effe dicunt folidatam cum Limo. Aldrcvandusthought it form’d of the disunited particles of what he calls the fatter stones, such asthe lime. stones wasli’d from them by the motion of the water, and afterwards gottogether in this form ; and Dalbschamp, who has come nearest the truth of any, esteem’dit a Chalk produced about the shores, a Creta litoralis, which he adds was veiy white,fat, and glutinous, and could not be dug up without taking some of die mud of theshores along with it. It is very clear, however, that according to this very account, thesubstance could be no chalk; viscidity and fatness, are qualities that cannot belong toan Earth of that class, neither are we indeed to imagine it was ever dug up -from theslat parts of the shores; since if there was there a stratum of it, tho' ever so thin anone, it might certainly have been taken up pure from it. Upon the whole it appearsmost probable, that there are strata of this Earth fine and pure in the clifts there-abouts, that the sea in storms and high tides washes off fragments of them, and thatthese are afterwards tofs'd about on the shores, and there acquire -the shells, &c. ofwhich they are always full.

It was much esteem’d in painting among the ancients, but now is entirely un-• known. Tho’ it might easily be Had, and readily parts with all its foulness in washing.

2 . Argilla levijjima alba friabilis.

Light , friable , white Clay.

This is a, fine and very beautiful Clay, of a pure snow white, and never con-tracting ’a yellowness from the .air, as the other white Clays are apt to do on their sur-face. It is of a soft friable texture, and the lightest of all the known Clays,' dryand not ‘ductile while in the stratum in any thing near the degree of the others,of a smooth surface, very soft to the touch, and stains the fingers in handling; it verystowly diffuses itsejf in water, and does not melt in the mouth till after it has beenheld there some time, and then but very imperfectly and disagreeably; it adherespretty firmly to the tongue, and leaves a harsh grittyness between the teeth.

Examin’d by the Microscope it appears of a most compact, close and regular texture.

It makes no effervescence with Aqua Fortis.

In the fire it burns to some but not much additional hardness, without any changeof colour; but in a very violent one affords a pale sea green glass.

It is dug in the Isle of Wight, and is much us’d for making tobacco pipes, tho’it will not serve that purpose alone, but must be mix’d with another coarser Earth,next to be described, which Is common in the fame place, and in many other partsof England, this fine Earth alone not having a due tenacity. It is said to be also agood medicine in fevers.

3 . Argilla ponderosa alba dura .

Hard t heavy , white Clay .

This is the Cimolia alba of the shops, the Argilla alba Charlt. Eos. 1. and theTerra Candida Saponaria five Fullonica, Kentm. 1.

It is a dense, compact, heavy Earth, of a dull white colour, and close texture,hard, dryish, and not so ductile while in the stratum as most of the other Clays; of atolerably smooth surface, not easily breaking between the fingers, and slightly staining

the