has been thought. This phlogifton is manifeft by analyfis
in the leaves, where the leaft atom of iron has never
been difcovered.
There are many lands in Spain which naturally produce
falt-petre, fea-falt, and vitriolic falts ; but the plants
which grow fpontaneoufly in thofe foils, give by analyfis
the fame produX as thofe of their fpecies in gardens,
where there never was any appearance o f falt-petre, fea-
falt, or vitriolic acid.
Analize as often as you pleafe, thofe plants fo numerous
near iron mines, whofe roots penetrate into the very
ore, or thofe that grow in ferruginous' and fuper-
ficial earth. I am fure you will not colleX from their
roots, branches, aihes, extraXs, or oils, more iron, than
what is found in the fame fpecies of plants that fpring
up in places without the leaft communication with any
fuch minerals.
Whatever efficacy there may be in culture, and manure,
to remove, abforb, and open the pores of the
earth, enriching the watery particles, that rife in the
vegetative tubes, conveying new fubftances. which contribute
to that perfeXion, we obferve, from the foil,,
and which they lofe when tranfplanted, yet they ftili attain
tain various fubftances o f vegetation from the air, which
chemifts may look for in vain in the earth (a).
Many plants are emollient in the fpring and fummer,
and aftringent in autumn and winter. Their mucilaginous
quality admits o f alteration in the tubes, and the
combination of earth, air, and water, engenders a vitriolic
acid(3), juft as the alkali and the leaves receive colour
from the phlogifton; from whence I conceive the
reafon of the nitrous foil in Spain, abounding with fuch
a prodigious quantity of fixed natural alkali; which calls
to my mind what is fondly advanced by the adepts,
“ That fome lands have the natural properties o f load-
ftone to attraX peculiar fubftances from the air.”
It is certain then, that plants have proper tubes to
attraX the elements, and form a natural fixed alkali, and
have peculiar feparate principles which only combine
by the means of fire in the aX of combuftion to form
that-artificial fixed alkali I had been taught to believe
was the only one that exifted in nature.
(a) The ingenious author of this reafoning does not feem to be aware, that it would be equally
fruitlefs to look for thefe fubftances in the .water, or in the air. It is true that we cannot extrail
turpentine from the fand, or from the earth, in which the fir trees o f Vallidolid and
Tort-ofa grow, but it is equally true, that we .cannot extrail it either from the air, or from
the water o f thofe. countries.
m, The exiftence o f ■vitriolic acid in vegetables has not yet been proved.
Perhaps