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And accordingly he obferves, that the Leaves next 
adjoining to the bloffoms are in the fpring very much 
expanded, when the other Leaves on barren fhoots 
are but beginning to fhoot, and that all Peach Leaves 
are very large before the bloffom goes off. 
And that, in Apples and Pears, the Leaves are one- 
third or half grown, before the bloffom opens, fo pro- 
vident is nature in making timely provifion for the 
nourifhing the yet embryo fruit. 
He alfo adds another experiment : he ftripped the 
Leaves of an Apple-tree branch, and then fixed the 
great end of the Idem in the gage, it raifed the mer- 
cury 2 + L inches, but it foon lubfided, for want of 
the plentiful perfpiration of the Leaves, fo that the 
air came in aim oft as fall as the branch imbibed 
water. 
And as a farther proof of the influence of the Leaves 
in raiding the fap, he alfo made the following expe- 
riment. 
On the fixth of Auguft, he cut off a large Ruffet 
Pippin, with a ftalk i + 4 - i nc h long, and twelve ad- 
joining Leaves growing to it. 
He cemented the ftalk faft in the upper end of a 
tube, which tube was fix inches long, and one- 
fourth diameter •, as the ftalk imbibed the water, it 
raifed the mercury four inches high. 
That he fixed another Apple of the fame fize in the 
fame manner, but firft pulled off the Leaves, and it 
raifed the mercury but one inch •, that in the fame 
manner he fixed a like-bearing twig, with twelve 
Leaves on it, but no Apple, and it raifed the mercury 
three inches. 
He then took a like-bearing twig, without either 
Leaves or Apple, and it raifed the mercury one- 
fourth of an inch. 
So a twig, with an Apple and Leaves, raifed the 
mercury four inches •, one with Leaves, only three 
inches ; one with an Apple without Leaves, only one 
inch. 
A Quince, which had two Leaves juft at the twig’s 
infertion, raifed the mercury 2+4 inches, and held 
it up a confiderable time. 
A fprig of Mint, fixed in the fame manner, raifed 
the mercury 3 + 4. inches, = to 4 feet 5 inches 
height of water. 
Thefe, and many more experiments of the Rev. Dr. 
Hales, that curious enquirer into the caufes, ftate, 
and progrefs of vegetation, evidently fhew the great 
perfpiration of the Leaves of plants, and their great 
ufe in railing the fap, and other functions of vegeta- 
ble nature ; to whofe excellent treatife before-men- 
tioned, I refer the curious enquirer. 
I fliall add. That nature has direfted us as to the 
true diftance we ought to train the branches of trees 
againft wails or efpaliers, which fhould always be in 
proportion to the fize of their Leaves ; for if we re- 
gard her progrefs in the great varieties of trees, which 
are within our obfervation, we fhall always find their 
branches grow diftant from each other in proportion 
to the breadth of their Leaves •, and it was upon this 
account that the Romans fo much admired the Plata- 
nus, becaufe the Leaves, being large, afforded them 
a kindly fhaae in fummer, but in winter, when they 
are deftitute of Leaves, their branches growing at a 
great diftance, eafily admitted the beams of the fun. 
I fhall next beg leave to mention a few, out of the 
many experiments which have been made by Monf. 
Bonnet, of Geneva, to prove that molt Leaves im- 
bibe the moifture of the air on their under furface, 
and not from their upper : they are as follow : 
He gathered the Leaves of fixteen forts of herba- 
ceous plants when fully grown ; of each he put feveral 
Leaves upon the furface of water in glafs vafes, fome 
were pofited with their upper furface, and others with 
their under furface upon the water ; thefe were ad- 
jufted exadtly to the furface of the water^ with great 
care not to let any moifture reach their oppofite fur- 
faces, and the iame care was taken to prevent their 
foot-ftalks from receiving any moifture. The glaffes 
in which thefe Leaves were thus placed, were kept in a 
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clofet, where the air was very temperate •, and as the 
water in the glaffes evaporated, there was from time 
to time a fupply of frefh, which was added with a 
fyringe, fo that the Leaves were not difturbed. The 
Leaves were taken from the following plants ; the 
Plantain, the Mullein, the Wake Robin, the great 
Mallow, the Nettle, the Marvel of Peru, the Kindney- 
bean, the Sun-flower, the Cabbage, the Balm, the 
Cock’s-comb, the purple-leaved Amaranth, Spinach, 
and the finaller Mallow. 
Six of thefe forts he found continued green a long 
time, and thefe were with different furfaces upon the 
water ; they were of the following forts, the Wake 
Robin, the Kidney-bean, the Sun-flower,* the Cab- 
bage, the Spinach, and fmall Mallow ; among the 
others the following forts were found to draw the 
moifture better with their upper furface than their 
under, the Plantain, the Mullein, the great Mal- 
low, the Nettle, the Cock’s-comb, and the purple 
Amaranth. 
The Leaves of the Nettle whofe under furface was 
upon the water, were decayed in three weeks, whereas 
thofe whofe upper furface was next the water conti- 
nued two months. 
The Leaves of Mullein, whofe under furface was 
next the water, did not continue frefli more than five 
or fix days, but thofe whofe upper furface was next 
the water lafted five weeks. 
The Leaves of the purple Amaranth, whofe upper 
furface was next the water, continued frellh three 
months, whereas thofe whofe under furface was next 
the water, were decayed in a week. 
The Leaves of the Marvel of Peru and the Balm, 
appeared to have the advantage, whofe under fur- 
faces were next the water. 
The Leaves of Wake Robin and of the Cock’s- 
comb, whofe foot-ftalks only were put into the wa- 
ter, continued frefli a longer time than thofe which 
were placed with either furface next the water. 
The Leaves of the Great Mallow, the Nettle, the 
Sun-flower, the Marvel of Peru, and Spinach, whofe 
foot-ftalks were plunged into the water, continued 
frefh a fhorter time than thofe which had either of 
their furfaces next the water. 
The Leaves of the Mullein, of Plantain, and Ama- 
ranth. which received the water at their foot-ftalk, 
continued frefh much longer than thofe, whofe under 
furface was next the water. 
It is not difficult to explain the reafon of this fa< 5 t, 
for the orifices of the fap-veffels in the foot-ftalk, 
are much larger than thofe of either furface, fo that 
the moifture infinuates in greater quantities, and with 
more eafe, the firft than by the fecond way. 
After this the fame gentleman made experiments on 
the Leaves of fixteen forts of trees and fn rubs of 
the following forts, the Lilac, the Pear-tree, the 
Vine, the Afpen, the Laurel, the Cherry-tree, the 
Plumb-tree, the Horfe Chefhut, the White Mul- 
berry, the Lime-tree, the Poplar, the Apricot, the 
Walnut, the Filbert, the Oak, and the Creeper. 
Among thefe fpecies, he found that the Lilac and 
the Afpen imbibed the moifture on their upper fur- 
face, equally with the under furface ; but in all the 
other forts, the under furface imbibed it in much 
greater quantities than the oppofite. The difference 
was very remarkable in the Leaves of the White 
Mulberry, for thofe whofe upper furface was laid 
upon the water, faded in five days, whereas the other 
whofe under furface was next the water, preferved 
their verdure near fix months. 
The Vine, the Poplar, and Walnut-tree are very re- 
markable inftances, how little difpofed the upper fur- 
faces of the Leaves of ligneous plants are to imbibe 
the moifture ; for thofe of thefe three forts, whofe 
upper furfaces were applied to the water, decayed al- 
moft as foon as thofe which had no nouriftiment. 
In all the experiments made by this curious gentleman 
upon the various Leaves of trees and herbs, it is re- 
markable, that all thofe Leaves which imbibed the 
moifture by their upper furface, were fuch as had 
that 
