4 
166 
‘ \ 
wich is 963954 feet; therefore the dif- 
tance ‘between Greenwich and Dankirk 
is 830196 feet. The diftance between 
Greenwich and Clifton is 722641 feet; 
hence, 4421968 fcet is the meridional 
Giftance between Clifton and Barcelona, 
The latitude of Barcelona is 41° 21'48/.8, 
that of: Greenwich, is 51°,"'28" gol, 
and if to the latter we add 1° 58’ 51.59, 
the arc between Clifion and Greenwich, 
pe fhali get 537 27’ 31.59, for the lati- 
tude of Cliften; hence the difference of 
latitude between Barcelona and Clifton 
is r2° 57 42".79, fomethicrg more than 
the 30th part of the whole circumterence 
of the earth. Wah this difference of 
latitude, and the above-mentioned dif. 
tance, we find the mean length of a de- 
gree on the earth’s furface in latitude 
47° 24' to be 60795 fethoms. ‘The lati- 
tude of Paris is 48° 50°15", which, com- 
pared with that of Clifton, gives 4° 37’ 
eg for the diifereoce between their 
parallels. The . meridional 
1686595 fect; hence 60825 fathoms is the 
length of the degree in latitude 51° 9’. 
By way of appendix to this valuable 
paper is fubjoined Tables of the bearings 
of the principal ftations in the counties 
of Effex, Suffolk, Kent, &c. from the 
aralle!s to the merician of Greenwich, 
and their diftances from that meridian. 
Alfo a Table of the latitudes and longi- 
tudes of the preceding ftations and ob- 
jeCts referred to the meridian of Green- 
wich. The accuracy of thefe tables may 
undoubtediy be depended upon, and, as in 
the latter, the numbers are carried cven to 
decimal parts of feconds, they will be a 
valuable addition to our topographical 
knowledge. : 
In the Philofophical Tranfaétions for 
the year 1805, Mr. Knight has recorded 
fome experiments on trees, from which 
he inferred, that their fap, having been 
abforbed by the bark of the roct, is car- 
vied up by the alburnum, cr white wood, 
16"".£9 
of the root, the trunk, and the branches 5’ 
that it paffes through what are there 
called the c-ntral veffels, into the fuccu- 
Jent pert of the annual fhoot, the. leat- 
ftalk, and the leaf; and that it returns 
to the bark, through the returning veficls 
of the leaf-#alk. In a paper lately com- 
munie?ted by the fame geuileman to this 
{foci tys his principal onject is to point 
out the caules of the defcent of the :ap 
through the bark, and the confequent 
formation of wood. ‘Thefe caufes appear 
fo be gravitation, motion communicated 
by w.nds or other agents, capillary attrac- 
ticn, and piobably fomething ia the con- 
Proceedings of Learned Societies. 
diftanee is. 
[March tl, 
formation of the veffels themfelves, which 
render them better calculated to carry 
fluids in one direction than ancthery 
Mr. Knight begins with the leaf, from 
which} be affumes, all the defcending 
fluids In the tree. aré derived. The 
efforts which plints always make to tum 
the upper furtdces of their leaves to the 
licht, have induced naturalifts to con- 
clude, that each furface has a totally 
difin& office, Mr. Knight has detailed 
a number of experiments to fupport that 
conclufioa. Fromthefe he infers, that in 
the vine the perfpiratory veflels are con- 
fined to the uncer furface of the leaf, 
and that they, like the cutaneous lympha- 
tics of the animal economy, are probably 
capable of abforbing moifiure when the 
plant is in a ftate to require it. The 
upper furface feems, from the pofition it 
afiumes, either formed to abforb light, or 
to operate by the influence of that body 5 
and if any thing exhale from it, it is’ 
picbably vital air, -or fome other perma- 
nently elaftic fluid. It is known, that 
perpendicular fhoots grow with greaier 
vigour than cthers, and Mr, Knight im- 
putes. it, from fome experiments, to a 
more perfe&t and rapid circulation. 
To prove the effeéts of moticn on the 
circulation of the fap, he fele@ed a 
number of young feedling apple-trees, 
whofe fems were about an inch in dias 
meter. By means of ftakes and bandages 
of hay, not fo tightly bound as to im- 
pede the progrefs of any fluid within the 
trees, he deprived the roots and lower 
parts of the items of feveral trees of all 
motion, to the height of three feet from 
the ground, leaving the upper parts of 
the fems and branches in their natural 
flare. In the fucceeding fammer much 
new weod. accumulated, in the parts 
which were kept in motion by the wind, 
but the lower parts of the ffems and 
roots increafed very little im fize. Re- 
moving the bandages from one of thefe 
trees, he fixed a ftake in the ground, 
about ten feet diftant from the tree oa 
the eaft fide of it, and attache! the tree 
to the fiake, at the height of 6x fe-t, 
leaving it liberty to mave towards the 
nerth and fouth, but in no other direc- 
tion. Thus circumfanced, the diameter 
of the tree from north to fouth, in that 
part of its fem which was moft exercifed 
by the wind, exceeded that in the oppo- 
fite direétion, in the fellowing antumn, 
in the proportion of 13 to rr. 
Heice we fee the means which nature 
employs to adapt the forms of its vege-. 
table productions io every fituation im 
| which 
‘ 
. 
ee a ee eee 
