Observations on the Manufacture of writing Ink . 
75 
It may readily be supposed that, if the end of the crecum, instead of being firmly 
closed, had been furnished with a small tube, the absorbed fluid, or endosmose, 
instead of producing an excess of turgidity, would have mounted in the tube. This 
M. Dutrochet found to be the case. He fixed the open end of a glass tube into 
the ccecum of a chicken filled with a solution of gum and water ; and having im- 
mersed the ccecum in rain water, and supported the tube in a vertical position, 
he found that in twenty-four hours the fluid had ascended to the top of the tube, 
and that it continued to ascend and overflow at the top for three days. On the 
third day the water began to sink in the tube; and on the fourth day, the 
ccecum being opened, the fluid was found to be putrid- The experiment was repeat- 
ed with the bladder of the carp, and with the inflated pod of the common bladder 
senna (Colutea arborescens), with equal success. 
The next thing that 31. Dutrochet endeavoured to discover was, the cause of 
fluids passing through organic substances possessing the action of endosmose and 
exosmose ; and, as the contact of bodies of different densities, as zinc and copper, 
is a well known cause of electricity, that power naturally occurred to him as suffi- 
cient to account for the phenomena related. He proved this by an experiment, 
which it would occupy too much room to relate, at sufficient length, to convey use- 
ful ideas to the general reader. The man ot leisure and science will have recourse 
to 31. Dutrochet's book ; and the gardener may safely adopt it as a proved fact, that 
that immense power, in a bleeding vine with a bladder t ed round the extremity, 
which Mr. Braddick (Hart. Trans., v. p. 202 ; found distended with the rising 
sap till it became as hard as a cricket ball, and which burst at the end of forty- 
eight hours, has been clearly traced to the difference between the specific gravity of 
the water of the soil, and that of the nutritious fluid contained in the almost invi- 
sible points, or spongioles, which form the extremities of the fibres of all plants. 
The effect of temperature on endosmose was, to increase the process, which is a 
proof of the influence exerted by electricity on the process ; it being a well known 
fact, that by increasing the temperature of two metals which produce electricity, 
the electrical current is increased in intensity. , , 
In applying his observations to the vital statics of plants, M. Dutrochet s tur- 
gidity is shown to be produced and maintained by endosmose, and the accumulated 
sap reacted on liy the natural elasticity of the sides of the minute organ* which con. 
tain it. Endosmose in the leaves takes place, to supply the vacuum which is created 
by the transpiration of water from their surfaces. This explains t e leason w i> 
cut plants absorb water, and why the roots and stem of a plant supply what sap 
!V have to the leaves, after being taken out of the ground. The difference _of 
t-uey iiave lu iuo jonvea, tuict - . T ° , n • • r 
plants, in regard to the temperature they require for the flowing or rise of the 
sap, is known to vary materially iu different plants ; and M. Dutrochet, with 
great apparent reason, thinks this is attributable to their differen piysica cap 
cities for producing electrical currents. - 
The substance of M. Dutrochet's theory may thus be summed up. T1 he i sap of 
plants does not circulate; it ascends from the root in the n, l t X e rice 
woody parts of steins and branches, and, being elaborated mto nutritive juice, 
descends by the vessels of the hark. The sap in ascending, apd =n the 
ing, are diffused laterally by horizontal vessels, which meet m W 
between the bark and the wood. The sap ansl proper juice ;‘t ‘H.ro l uM t s 
space, and these unite and form increments both of bark and i iwo d - 
of the sap and juice in plants take place m consequence of the operat.ions oi twods 
become turgid ; and the other positive, by which the i 
power M. Dutrochet calls exosmose. Dutrochet’s experiments 
It is gratifying to find, that none o • K„ight : in some minor points 
are materially at variance with the opinions ot • g Knicht arp confirm- 
their hypotheses differ , tat all the 
ed and established by 31. Dutrochet, on a basis 
IV . — Observations on the Manufacture of un iting Ink. By Dr. Ure. 
[From the 3d vol. of the Mechanic’s Magazine.] 
Common ink for writing is made by adding an infusion or decoction of the nut- 
gall to sulphate of iron, dissolved in water. A very fine bl,'.* prec.pnate is hrown 
down, the speedy subsidence of which is prevented by the addition of a propei quan- 
