The Middlebury register. [volume] (Middlebury, Vt.) 1850-1882, 1879-05-09

feature of this fact is, that though APP
parently produced by eXhalation from
the expanding leaves, it remained the
same, day and night, for several weeks.
In June the suction gradually lcssened,
and finally disappeared, the mercury
standing steadily at zero.
On the Goth of April two gauges were
attached to large, black birch, one at
the ground, and the other thirty feet
higher. The next morning at six
O'Clock the lower gauge indicated the
astonishing pressure of $500 feet of
water, and the upper one, of 26.74 feet.
The difference between the indications
of the two gauges was thus 1892 feet,
while the actual distance between
them was 1920 feet, so that it CORE
sponded almost exactly as if they were
connected by tube. In order to learn
whether the same principle would pre-
vail if the upper gauge was moved, ii
was raised twelve feet higher. The
same correspondence continued through
nearly all the observations of the sea-
son, Notwithstanding the gauges were
separated by 1920 feet of cose-graincd
| brentwood.
AT 1890 p. NJ, April 81, n hole was
bored into the tree on the side opposite
to the lower gauge, and at the same
level. Both gauges mt once began TO
show diminished pressure, while sap is
sued freely from the oriiice. In fifteen
minutes, one pound of sap having cs-
capped, it was found that both gauges
had fallen equal TO 1927 feet of water.
Upon closing the hole the gauges rose
in ten minutes to their previous level.
showing that the rootlets had re-ab-
sorbed in that brief period the sap
which had escaped from the tree, not
withstanding the enormous pressure al
ready existing.
A stopcock having been inserted into
the hole opposite the lower gauge, ii
was found that the communication be-
tween it and the two gauges was al
| most instantaneous, which appears to
prove that the tree was entirely filed
with sap, exerting its pressure in all
directions rs freely as if standing in a
cylindrical vessel more than sixty feet
in height, as indicated by the lower
gauge. The sap-prcssure continued TO
increase until, on the 18th day of May.
| ii represented column of water S4.li
feet in height, which is believed to be
the highest pressure of vegetable sap
|
ever before recorded.
The buds of the birch now began 10
expand, the pressure of the sap to di-
minish, and.the oscillations of the mcr-
curry to become more decided and regu
lar than before. The upper gauge
ceased to vary May IA, remaining sta
tionary at zero. The lower one de-
clined slowly and varied greatly, but
did not fall below zero until May lS.
On May az it also became stationary nj
zero. The suction manifested by tho
birch was very little, never exceeding
for few days.
To determine, if possible, Whether
and other, force than the vital action OF
the roots was necessary to produce the
extraordinary phenomena described, {
gauge was attached to the root of q
black brch-tree, as follows: The tree
stood in moist ground, at the foot OF
the south slope of n ravine, in such q
situation that the earth around ii was
shaded by the overhanging bank from
| the sun. A root was then followed
from the trunk to the distance of tel
feet, where it was carefully cut oil one
foot below the surface, and piece re
moved from between the cut and the
tree The end of the root thus entirely
detached from the tree, and lying in ;
horzontallpostion at the depth of foo
in the cold, damp earth, unreached b!
the sunshine, and for the most part un
affected by the temperature of the at
.hosphere, measured about one inch il
diameter. To this was carefully adjust
cd mcrcurial gauge, April 26. Tht
pressure at once became evident, an(
rose constantly with very slight fluctu
ations, until, at noon on the 3Oth o
April, it had attained the uncquallct
height of S5 80 of water. This wonder
full result showed that tho absorbing
power of living birch rootlets, withou
the aid of the numerous helps imposeI
upon them by ingenious philosophers
such as exhalation, capillariiy, oscilla
tion, dilataiion, contraction, etc, etc.
} was quite sufficient to account for TN
most essential of the curious phenom
ena connected with the circulation o
sap. Unfortunately, in an attempt +
increase the capacity of the gauge, III
bark of the root was injured, and thi
most Interesting experiment terminal
ed. There can be little doubt that fl
, lure trials, carefully conducted wit
suitable apparatus, will achieve eve
more marvellous results.