E X P L A I N E D BY THE MICROSCOPE.
conftrudtion of this Microfcope admits : nor are the means of more aiTiftance wantingj PLATE
fince coloured liquors may be thrown into the fmall veflels of Plants; and, into the very
fmalleft of all, liquors, which tho' pellucid and colourlels when received, may be
coloured after they are lodged there j altho' the matter of that colouring would have
rendered the liquid too thick to have palTed in the fame condition.
As the veflels of the Rind are of different diameters in various trees, tho' their cortftruftion
and that of the Blebs is perfetitly the fame in all; it will be beft to choofe for
this purpofe the Rind of a tree wherein they are largeft. The advantages I received from
the garden of her late Royal Highnefs the Princefs Dowager of Wales, at Kew, (who,
beft of Princefles and of Women! was pleafed, -undcferving as I am, to honour me
with her royal patronage and proteftion,) that garden, where every tree that has been
feen in Europe is at hand, have given me opportunities of fo many trials, that I can
happily fave the pains of others in this and all the following inftances 5 by faying what
beft anfwers: to the prefent purpofe the Rind of the Aih-lcaved Maple is finely
fuited. A piece of this may be obtained of two inches long, and will very fuccefsfully
anfwer the intention. Such a piece being prepared without either alum or fpirit,
but dried from the water in which it had been macerated, is to be impregnated with
lead in the following manner j to Ihew the apertures by their colour.
DiiTolve one dram of fugar of lead in an ounce and a half of water: filter this thro'
paper, and pour it into a tea-cup. Clip off a thin fliceof what was the lower end of the
piece of Rind, as it grew on the tree, and plunge it near an inch deep in the liquor j
keep it upright between two pieces of ftick, fo that one half or more may be above
the water: whelm a wine and water glafs over the tea-cup, and fet the whole in a
warm place. When it has ftood two days, take it out, and clip off all that part
which was in the liquor, and throw it away.
The circumftances here mentioned, trivial as they may feem, muft be attended to :
the operation will not fucceed even if the covering glafs be omitted : it keeps a moift
atmo^here about the Rind, and makes its veflels fupple.
While this Is ftanding, put into a bafln two ounces of quick lime, and an ounce of
orpimentj pour upbn them a pint and a half of boiling water; ftir the whole together
J and when it has ftood a day and night, it will be fit for ufe. This is the Liquor
Probatorius Vini of fome of tiie German chymifts: it difcovers lead when wines are
adulterated with i t j and will ftiew it any where.
Put a little of this liquor in a tea-cup, and plunge the piece of Rind half-way into it.
In the former part of this experiment the vefl'els of the Rind had been filled with a
folution of lead; that makes of itfelf no vifible alteration in them : but this colourlefs
impregnation, when the Orpiment Lixivium gets to it, becomes of a deep brown;
the veflels themfelves appear fomewhat the darker for i t ; but thefe dots, which are
real openings, now are feen to be plainly fuch, the colour being perfeiiHy vifible in
them, and much darker than in the veffels. Plate V. Fig. i. a i .
This
Fig. I.