THRAUSTOMICTHES.

42Z

and is harsh, but less coarse than most of the other Loams between the teeth ;thrown into water it raises a flight ebullition and hissing, and after a few minutesmoulders into a loose powder.

Examin’d by the Microscope, it appears of a somewhat spungy, but for a Loam, afine and even texture, and is compos’d of a very fine white Sand, lodg’d in a pale brownClay.

It makes a violent effervescence with Aqua Fortis.

In the fire it acquires a great hardness, and pale red colour.

It is dug in many parts of the kingdom, and makes a very firm and valuable palered brick; there is a thick stratum of it in the great Clay-pit behind St. George’s Hospi-tal, at Hyde-Park-Corner, but they don’t work it there alone, but mix’d with theother Clays of the pit, which together make very fine and hard brick : It lies there atabout nine feet deep.

3 -

ThrauJlomiElhes pallide flavefcens.Pale yellow ThrauJlomiElhes.

This is a very friable and spungy Earth; while in the stratum, it is of a loose in-coherent texture, harsh and dry, and cuts thro’ easily but very irregularly with thespade, falling in irregular masses, and leaving a rough uneven surface behind it; whendry, it is of a loose, spungy and incoherent texture, of a pale yellow, spangled overWith a multitude of shining particles, and of considerable weight: It is of a rough,uneven, but not dusty surface, adheres pretty firmly to the tongue, is harsli and dry tothe touch, easily crumbles between the fingers, and does not stain the hands ; it meltsVery freely in the mouth, and is very coarse between the teeth; thrown into water, itremains quiet about half a minute, but after that makes a flight ebullition, with a con-siderable hissing noise, and immediately after falls into a loose powder.

Examin’d by the Microscope, it appears of a very spungy texture, compos’d of awhite Sand, held together by a yellow Clay, and spangled with small thin plates of afoliaceous Talc.

It makes a very brisk effervescence with Aqua Fortis.

In the fire it acquires a very fair red, with a considerable hardness.

It is dug in most Counties in England, but never used alone in brick making; work’dUp with the tougher Clays, makes together a very strong brick.

4. ThrauJlomiElhes fiavescens, durior W afipera.

Sharp , rough , yellow ThrauJlomiElhes.

This is a very harsli and rough, but a very valuable Earth; while in the stratum,tt is very moist, cuts easily and evenly with the spade, and leaves a smooth surface be-hind it; when dry, it is extreamly hard, of a strong yellow colour, sometimes variega-ted with white, of a coarse but very compact texture, and great weight; it has a rough^'regular surface, adheres slightly to the tongue, is very harsli to the touch, and doesuot easily break between the fingers, nor at all stain the hands; it melts readily in theutouth, and is extreamly coarse between the teeth ; thrown into water, it makes a flighte bullition and hissing, and soon falls into a loose powder.

View’d before the Microscope, it appears of a very rough texture, and compos’d ofa coarse yellowish Sand held together by a pale yellow, and in some few places by awhitish Clay.

It makes no effervescence with Aqua Fortis.

It burns to a fine deep red, and very great hardness.

It is dug near the Town of Hedgerley, five Miles from Windsor, and in no otherplace that I know of; it lies there at a very considerable depth, and is not to be dugn °w without very great expence; it makes the bricks us’d in building furnaces forpelting iron, and endures even the glass-house fires; beside these uses, it is also theIdlest 0 f a p l u tes in Chymistry, and fells at a very considerable price. It is not onlysought to London, but sent into all parts of the kingdom, and not a little of it intoGermany and Holland.

Vol. I.

5O

5. PhrauJlomiEihes