—o— posed. Botrychium : 
Natural 
filters or 
Fig. 8, must t 
with the rest of the series of ferns; for, 
the fronds.* | 
_ FILIGRANE Wonk, or Finacree work, from j- 
lum and granum, is the name given to a kind of orna- 
mental work, in which flowers, &c, are formed of fine 
and silver wire, curled or twisted ina 
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uk 
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employ: 
Such of our readers as take any interest in 
j referred to the following works, quot-. 
: ann in his History of Inventions, vol. ii. 
245—247. 
, 's Werkstate. der kiinste, i. p. 101; 
i Worterbuch, i. p. 721; Grignon Bul- 
letin des fouilles d'une ville Romaine, i. p. 22.; Menage 
reliquiarum Electoralis Brunsuico-Lunebur- 
i Hanov. 1783, 4to. p.19, 29, 56. Marsden’s 
i of Sumatra, Lond. 1783, 145. Der Mi- 
i Briefe van der Insel Teneriffa und Os~ 
tindien, Leips. 1777.. Thomans Reiseund Lebensbes- 
, Augsb. 1788; and Von Stetten Kunstges- 
bg: 'P 
are in the toward the water 
Seligl vided taki end werehdloteme fee damentie 
purposes: such is the state of the waters of most rivers 
which are not supplied by springs alone, but by brooks 
running on the surface. portion of the water 
which soaks into the earth having passed through a 
sufficient thickness of strata, either by ascent or 
descent, will have op mang rpciec pumping 
and become clear spring water, It be observ- 
ed, that filtration can only produce transparency, by 
NG OE Ree ett 28. 50 ic vise of 
mixture with the fluid, for any matter 
pass with it, ‘the pores most minute. fil- 
ter, unless the substance of the filter itself should have 
a greater af for such matter than the fluid which 
it. this case, a new combination will be 
: 
E 
will be taken up by the filter, not simply because the 
are too small to permit its particles to pass, 
on account of the superior elective attraction be- 
345 
tween the substance of the filter and the dissolved mat- Filter. 
™ : 4 ———’ 
_ poses the filter a 
FIL 
ter. 
duce a natural spring for any great 
cause, by the constant addition of matter, the filter will 
at last saturated with it, or choked up. In ~ 
applying this reasoning to springs, we shall find a rea~ 
son why so few springs uce water, although 
it is always transparent. In ty, the natural 
filters-which produce springs, are almost always on an 
opposite principle, viz. that the substance which com- 
t affinity for the water, and 
a are taken up slowly in solution, 
carried off at the same time that the extrane- 
ous matters, which are only in mixture with the water, 
are detained in the pores of the filtering strata: thus 
we find few springs which have not some mineral held 
in solution by the water, although invisible to the eye ; Frequently 
and in cases where yn ere in making the new ""P4"* 
combination we have en of, hot springs will be 
produced. The most common mineral taint which wa- 
ter receives in its natural filtration, is sulphate of lime 
or plaster of Paris: this renders the water hard, as it 
is called, so that it will not produce a lather with soap, 
but curdles it. — tip and vitriol is also fre- 
in springs. Add to this, in great towns, the 
dnnnage wate which soaks into the earth is contami- 
nated by animal matters as well as vegetable, and in 
such an offensive state, that the filtration through the 
soil can scarcely restore its purity. From all these 
causes, it is found that the turbid and foul waters of 
rivers, where altered by art to separate from their extra- 
neous mixtures, will be more pure and wholesome as . 
RS te than the generality of spring water. 
Gravel, 
the water in passing it. Beds of sandstone filter 
only well, and also some porous limestone. 
apparatus is made from a po- Filtering 
rous stone, of which there are two kinds ; staniietene tne, 
procured in Northamptonshire, and a limestone found 
in Derbyshire. A thick bow] or basin is formed of the 
stone, and mounted in a frame. The foul water, be- 
aieage mpi basin, 
HE 
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: 
"© The Editor has been indebted for the preceding article, to Joux Your, M.D. F.R. S. E. 
VOL. IX, PART L 
2x 
- Filtration, on this principle, cannot continue to pro- Their ac- 
of time;, be- tion. 
in thick beds, is the most ect natural Gravel 
ings from ‘Prings- 
