SUN 
eel up immediately, and put upon a plate of water, it 
feerns as though it would fuck it up into the glafs ; 
when indeed the truth of the experiment is, that it is 
only the outward preffure, and the inward weaknefs 
of the air to refill, being purified by heat ; for if the 
fame glafs fhould be plunged into a bafon of water up 
to the foot of It, yet the water that is In the bafon 
would not enter into the glafs, till the air, either hav- 
ing loft its own ftrength, or rather infinuated or incor- 
porated itfelf in the water, lofes its own ftrength ; fuch 
is the force of air. 
But this may fuffice concerning what the ancients call 
attraction, which in many cafes is folved by pulfion, 
or the preffure and elaftic power of the air, rather 
than by the attractive power of the Sun. 
It is fufficiently proved by ocular demonftration that 
the vapours of the fea, rivers, lakes, and all the hu- 
midities of the ground, are drawn up after this 
manner. 
And that heat is an agent in this operation has been 
clearly proved by the experiments of that learned na- 
turalift Dr. Halley, by taking a veffel of water four 
inches deep, and feven and nine tenths in diameter, 
which being warmed to fuch a degree, as might be 
fuppofed the air might do it, in fome of the hotteft 
months, and letting it Hand about two hours time, 
and weighing it, found it had evaporated near half 
an ounce, although there did not appear any reek or 
fmoke, nor did the water feem warm, by putting his 
finger into it; from which it may be concluded, that 
out of that fin all fuperficies of the water, fix ounces 
would be evaporated in the fpace of twenty-four 
hours. 
Upon this fuppofition every ten fquare inches of the 
furface of water yield in vapour, per day, a cube inch 
of water ; and each fquare foot, half a wine pint ; 
and every fpace of four feet fquare, a gallon ; a mile 
fquare, 6914 tuns-, a fquare degree, fuppofe of 69 
Englifti miles, will evaporate 33 millions of tuns. 
This will account for the Cafpian fea being always at 
a ftand, and neither wafting nor overflowing ; and 
alfo for the current faid to fet always in at the 
Streights of Gibraltar, notwithftanding that thofe 
Mediterranean Teas receive fo many, and fo confide- 
rable rivers. 
This experiment has been carried yet farther by the 
Oxford Society, who, fuppofing a cubical foot of wa- 
ter to weigh 76 pounds, and this foot containing 1 728 
cubic inches, and divided in the 76 pounds, gives 
half an ounce and 1 3! grains, which is the weight of 
a cubical inch of water ; therefore the weight of the 
233 grains 444, or 35 parts of a cubic inch divided 
by thirty-eight. 
Then the area of a circle, the diameter of which is 7 
inches and upwards, is more than 49 fquare inches, 
which if it be divided by 44 parts of an inch, the 
quantity of water carried off in vapours, the produd 
will be or 44 parts of an inch, wafted in that 
experiment. This is a plain proof of what a great 
quantity of water may be thus carried off, in great 
dimenfions of water, even enough to fupply all rains, 
dews, &c. 
But the Sun, befides this, has a diffufive power (not 
to dwell on the light it conveys to thefe fublunary 
regions) without which the whole race of mankind 
muft wander and grovel in the dark, for by its genial 
and chearful rays it exhilarates the vegetable part of 
the creation, and makes natures herfelf to fmile. 
It has an influence upon deep grounds by warming 
and chearing the pores of the earth, when diluted and 
fodden by too much wet, and puts the emulgent fi- 
bres of plants upon feeking their food. 
It helps the furface of the ground by attrading or 
difpelling the vapours, which would otherwife make 
it noxious •, but more particularly it warms and heats 
the ground, and by its powerful influence contributes 
to diffolve the latent fait, and prepares them for being 
fucked in by the fibres of the plants, which, by the 
fame genial force, are put in adion to feek out for 
their food. 
SUN 
The Sun alfo exhales all fuperfluous ffioifture, and by 
its vital heat, comforts the dilated pores. 
The Sun diffufes the early dews, which, if they lay too 
long on plants, would rot rather than refrdh them j 
it alfo preffes them into the nerves, and other analo- 
gous parts. This influential power operates on the 
boughs, branches, leaves, and fruit. 
The Sun alfo qualifies the air, which otherwife, by 
its frigidity, would flop the very courfe of nature, and 
indeed it would be difficult to inftance any thing iri 
the whole circle of botanology, that does not partici- 
pate of a ffiare of this virtual and diffiifive good. 
From what has been faid we may eafily account for 
the difference of heat in fummer and winter, viz. from 
the obliquity of the Sun’s rays. This therefore fhould 
be well confidered in the contrivance of ftoves, to 
preferve the mod tender exotic plants, which ought 
to have their glaffes fo fituated, as to receive the Sun’s 
rays in diredt lines as great a part of the year as 
poffible ; for which realon the ftoves, which have 
upright -glaffes in front, and Hoping glaffes over 
them, are juftly preferred to any at prefent contrived. 
And from hence we fee the advantage of making the 
back part and deling of all green-houfes and ftoves 
as white as poffible, fince it is evident, that the rays 
of light are hereby refle&ed with much greater force, 
and lb confequently the heat is greatly increafed, 
which fhould always be obferved in buildings of this 
kind. 
From hence alfo we may learn, that countries in the 
fame latitude may be very different in their heat, ac- 
cording to their fituation, in refpedl to the Sun’s rays, 
or according to the nature of the foil in refle&ing the 
rays with a greater or lefs force ; fo that in preferving 
exotic plants, the heat which they require cannot be 
exadly determined from the latitude of the places of 
their growth ; but the fituation of the places muft alfo 
be confidered, as, whether they grow on hills, moun- 
tains, or valleys ; and if on the fide of hills, which 
fide in refpedt to the Sun, withfeveral other obferva- 
tions, which ought to be made by fuch as colled plants 
in foreign countries. 
I fhall here add a table of the lhadow of the Sun at 
the feveral feafons of the year, whicliwas communi- 
cated to me by Mr. Timothy Sheldrach of Norwich, 
by which a perfon may more readily fee what effed 
walls, buildings, trees, &c. have, in (hading the ground 
to feveral diftances, according as the Sun is more or 
lefs elevated above the horizon ; as alfo how great 
the (hade will be in the green-houfes, as the piersare 
in breadth, or the wall in front is in height below the 
faffies. 
O in 23 | 
O in 
-rv 
<r 
O in kf 
Lat. 
5 ,c 
3 °' 
Degr. of Lat. 
O 
/ 
// 
| Degr.of Lat. 
O 
J 
// 
Degr.of Lat. 
O 
/ 
// 
The lengt 
dow of 
five fee 
time tf 
every fi 
O in 
[1 o] 
a c 
t h 
e f 
gn- 
0 
the fha- 
olumn of 
gh at the 
un enters 
1— < 
3 
— 
— 
— 
— 
— 
— 
— 
— 
— 
— . 
5 feet 
cd 
r-t 
3 ° 
4 ° 
— 
8 
l 7 
3 ° 
OO 
— 
10 
22 
3 ° 
0 
10 
— 
l 7 
37 
O O 
25 
z 
* 
5 ° 
— 
32 
3 ° 
3 ° 
— 
35 
— 
20 
— 
57 
30 
SI n 
3 
1 
60 
— 
47 
3 ° 
40 
— 
47 
3 ° 
3 ° 
1 
17 
— 
n. « 
3 
70 
1 
7 
3 ° 
5 ° 
1 
|io 
. 
4 ° 
2 
2 
3 ° 
JV op 
6 
6 
80 
1 
40 
— 
60 
1 
5 °< 
5 ° 
3 
40 
— 
rn. X 
2 
7 
90 
2 
37 
3 ° 
70 
240 
* 
— 
— 
f. 
4 - 
l 5 
5 
80 
10 
! 
1 
kf 
20 
The firft three tables (hew the length of (hadows in 
the fummer and winter folftice, and in the vernal and 
autumnal equinoxes. Suppofe a mountain, column, 
or other body, whofe perpendicular height is one de- 
gree. The length of the (hadow from any thing of 
that altitude is here (hewn in every degree of latitude 5 
at the above-mentioned times, in degrees and mi- 
nutes, and where a (horter meafure than a mile is 
required, it is (hewn in feconds. The fourth table 
is calculated for the latitude of 51 0 30', which i$ 
pretty near that of London. This fourth table (hews 
the length of the (hadow made by any perpendicu- 
