BOLES, 5

It is dug in many parts of the island, from whence it has its name, and us’d in theGerman shops, as a Cordial and Sudorific, and a remedy against venemous bites.

8 . Bolus alkalinasubcinerea , quæ terra Eretria authorum.

Whitish Alkaline Bole , the Eretrian Earth of authors.

This is the Terra Eretria. Math. 1392. Terra Eretria cinerea Ultramarina quaMedici Utuntur. Kent. 1. Eretria Terra Plin. L. 35. P. 686. and the grey EretrianEarth of Diofcorides and Galen.

It is a fine and pure Earth, of a greyish white, moderately heavy, and of a smoothpolite surface, not staining the hands, and readily crumbling between the fingers ; itadheres firmly to the tongue, and melts easily in the mouth, leaving a lasting smooth-ness on it, without the least harshness between the teeth.

View’d thro’ the Microscope, it shews an equal and regular texture.

It raises a very brisk effervescence with Aqua Fortis.

It burns to a perfect; whiteness, acquiring a stony hardness and an acrimonious taste,and in a violent fire runs into a very pure pale blue glass. But what abundantly distin-guishes it from all other Earths is, that if a little wetted and drawn over a plate of brass orcopper, so as to mark a line, the mark will in a little time appear blueish. This is a cha-racter originally recorded of it by Diofcorides,'and since copied from him by many otherauthors; it has appear’d to many a strange quality in an Earth, and been doubted by some,but experiments shew the accounts to be true ; and indeed it will appear the less won-derful, when we consider, that it appears by its fermenting so strongly with Aqua Fortis,to be manifestly a powerful Alkali, and that all Alkali salts readly draw a blue tincturefrom that metal; but since neither Chalk, nor any of the other Alkaline Earths will dothis, it is evident that this poffeffes that quality in a degree much superior to them all.

It is dug in the Negropont, near the ancient Eretria, and might be had in quantitiesif it were brought into use in medicine, as it anciently was; and its pecular Alkalinequality might very well recommend it to be at present.

The ancients were extreamly careful in their manner of preparing it for Use ; a de-scription of the method is given at large by Diofcorides, and amounts to a very sineway of levigating, analogous to that by which we now prepare our testaceous powders. Itstands recommended as a noble Astringent and Sudorific.

The ancients mention another Eretrian Earth of a pure white, but this was in rea-lity no other than the true white Bole of Armenia.

9. Bolus albo gri%ea alkalina durior.

Hard whitish alkaline Bole.

This is a hard, close, compact Earth, of a bright white, but not without some smallmixture of greyishness, of an even and plain but not polite surface, breaking verydifficultly between the fingers, and not staining the hands, unless when fresh broken.

It adheres but slightly to the tongue, is more readily diffusible in water than mostother Boles, and melts gradually in the mouth into a smooth substance, but not withoutleaving something of gritty ness between the teeth.

The Microscope shews it of a regular, but a less smooth surface than many of theother Boles.

It effervesces slightly with Aqua Fortis.

In a moderate fire it burns to a pure white, with but little additional hardness, and no sen-sible acrimony. In a violent fire it becomes a light spungy and greenish half vitrify’d mass.

It is found on the surface of the earth near Bengal, and in many other parts of theEast Indies; and after it has undergone three calcinations, is us’d by the natives influxes and fevers with great success.

These are all the white Boles mentioned by the ancients, or introduced into Use bylater Ages; and however alike they might appear to one another on a cursory view, orcloser examination, experiments shew them to be all manifestly different substances, andevidently so many distinct species of Earths. I am sensible that the accounts hithertogwen of them by authors, very little distinguish them from one another; and that nothingut e ciiptions made from the bodies themselves, and experiments made on them couldhave done it. What are their real uses in medicine remains with us yet to try, for atpresent hey are in a manner unknown in our shops; but if we were inclin’d to give

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