firft has a degree of heat under the equinoctial line, 
and the other a degree of cold in 88 degrees north 
latitude. 
Thefe inftruments, the barometer, hygrometer, anc 
thermometer or Thermofcope, difcover the altera- 
tions of the air, as to wet or dry, efpecially if it be 
accompanied with a hygrometer •, and the thermo- 
meter thews the condition of the air, as to heat or 
cold. 
The method prefcribed to be ufed in keeping the ac- 
counts or obfervations made on the alterations of 
thefe inftruments, is that which was ufed by the Hon. 
Samuel Molyneux, Efq*, 
There muft be a book for the remarks in all the twelve 
months of the year, which are to be made fix times 
every day. At' thefe times you muft obferve, 
r. How the quickfilver rifes or falls in the barometer. 
2. What is the alteration of the hygrometer. 
3. How the fpirits in the thermometer rife or fall. 
4. From what point of the compafs the wind blows •, 
and alfo with what ftrength, according to the neareft 
guefs that can be made. 
5. Whether it rains, fnows, hails, &c. and in what 
quantity. 
Every leaf of the book is to be divided into feveral 
columns the firft for the day of the month and the 
week, the fecond for the number of inches and parts 
of an inch in the tube of the barometer, where the 
quickfilver ftands at the time when the obfcrvation 
is made. 
The fecond is to be for marking the degrees, which 
the index of the hygrometer points to at the fame 
time. 
The third is for fhewing the number of inches and 
parts of an inch, where the fpirits ftand in the ther- 
mometer at the time when the obfcrvation is made. 
The fourth is for marking from what point the winds 
blow, and their ftrength. 
The fifth is for noting the quantity of rain, &c. that 
falls, and what difpofition the clouds and air have. 
Take, for example, the following account of the 2d 
of June, 1721, which table is inferted underneath. 
According to this method, a weather book may be 
kept of the country a perfon refides in ; and by 
comparing the motions of the quickfilver and lpirit 
with the weather, at fuch times as the obfervations 
are made, a little praftice will enable a perfon to 
give a good judgment beforehand what weather will 
happen. 
The TABLE. 
Friday , Junei, 
I 7 21 * 
Barometer . 
Inch. Par. 
Hygrometer , 
•with :tt Di 
•vtfions ana 
Parti. 
T her mam. 
Wind. 
Weather. 
Morning at 9. 
29 
98 
240 
3 ° 
Eaft, brifk Gale. 
Cloudy. 
Noon. 
29 
9S 
260 
20 
28 
Eaft, brifk Gale, 
or ditto. 
Afternoon at 3 . 
29 
98 
280 
20 
28 
Ditto . 
Ditto . 
Afternoon at 6. 
29 
98 
300 
20 
27 
Ditto. 
Ditto. 
Evening at 9. 
29 
98 
3 1 5 
! 5 
28 
Ditto. 
Ditto. 
Midnight. 
29 
98 
320 
5 
28 
Ditto. 
Ditto. 
Mr. Boyle, by placing a thermometer in a cave, which 
was cut ftrait into the bottom of a cliff, fronting the 
fea, to the depth of 130 feet, found the lpirit flood, 
both in winter and fummer, at a fmall divifion above 
temperate ; the cave had eighty feet depth of earth 
above it. 
I, fays Dr. Hales, marked fix thermometers numeri- 
cally, 1, 2, 3, 4, 5, 6. The thermometer, number 
1, which was the fhorteft, 1 placed with a fouth af- 
ped in the open air •, the ball of number 2, I fet two 
inches under ground •, that of number 3, four inches*, 
number 4, eight inches number 5, fixteen inches ; 
and number 6, twenty Tour inches : and that the 
THE 
heat of the earth atthofe feveral depths may the more 
accurately be known, it is proper to place near each 
thermometer a glafs tube, fealedatboth ends, of the 
fame length with the Items of the feveral thermome- 
ters, and with tinged lpirit of wine in them to the 
lame height as in each correfponding thermometer *, 
the fcale of degrees of each thermometer being mark- 
ed on a Hiding ruler, with an index at the back of it, 
pointing to the correfponding tube. 
■VVhen at any time an obfervation is to be made, by 
moving the index to point to the top of the fpirit in 
that tube, an accurate allowance is hereby made for 
very different degrees of heat and cold in the ftems 
of the thermometers at all depths*, by which means 
the fcale of degrees will fhew truly the degrees of heat 
in the balls of the thermometers, and confequently 
the refpeftive heats of the earth at the feveral depths 
where they are placed. 
The ftems of thefe thermometers, which were above 
the ground, were fenced from weather and injuries, 
by fquare wooden tubes. The ground they were 
placed in, was a brick earth in the midddle of my 
garden. 
July the 30th he began to keep a regifter of their 
rife and fall : during the following month of Auguft 
he obferved, that when the fpirit in the thermometer, 
number 1, (which was expofed to the fun) was about 
noon rifen to 48 degrees, then the fecond thermome- 
ter was 45, the fifth 33, and the fixth 31 ; the third 
and fourth at intermediate degrees : the fifth and fixth 
thermometers kept nearly the fame degree of heat, 
both night and day, till towards the latter end of the 
month ; when, as the days grew fhorter and cooler, 
and the nights longer and cooler, they then fell to 2^ 
and 27 degrees. 
Now fo confiderable a heat of the fun, at two feet 
depth under the earth’s furface, muft needs have a 
ftrong influence in raiflng the moifture at that and 
greater depths, whereby a very great and continual 
reek muft always be afcending during the warm fum- 
mer feafon, by night as well as by day ; for the heat 
at two feet deep is nearly the fame night and day ^ 
the impulfe of the fun-beams giving the moifture of 
the earth a brifk undulating motion ; which watery 
particles, when feparated and rarefied by heat, afcend 
in the form of a vapour ; and the vigour of the warm 
and confined vapour (fuch as that which is one, two, 
or three feet deep in the earth) muft be very confi- 
derable, fo as to penetrate the roots with fome vigour 
as we may reafonably fuppofe from the vaft force of 
confined vapour in aiolipies, in the digefcer of bones, 
and the engine to raife water by fire. 
If plants were not in this manner fuppiied with moif- 
ture, it were impofiible for them to fubfift under the 
fcorching heat within the tropics, where they have no 
rain for many months together *, for though the dews 
are much greater there than in thefe more northern 
climates, yet, doubtlefs, where the heat fo much ex- 
ceeds ours, the whole quantity evaporated in a day 
there, does as far exceed the quantity that falls by 
night in dew, as the quantity evaporated here in a 
fummer’s day is found to exceed the quantity of dew 
which falls in the night. 
But the dew which falls in a hot fummer feafon cannot 
poflibly be of any benefit to the roots of trees ; becaufe 
it is remanded back from the earth by the following 
day’s heat, before fo fmall a quantity of moifture can 
have foaked to any confiderable depth. 
The great benefit therefore of dew in hot weather 
muft be, by being plentifully imbibed into vegeta- 
bles, thereby not only refrefhing them for the pre- 
fent, but alfo furnifhing them with a frefh iupply of 
moifture, towards the great, expences of the fueeeed- 
ing day. 
It is therefore probable, that the roots of trees and 
plants are thus, by means of the fun’s warmth, con- 
ftantly irrigated with frefh fupplies of moifture *, 
which, by the fame means, infinuates itfejf with 
fome vigour into the roots ; for if the moifture of 
the earth were not thus actuated, the roots muft then 
receive 
l 
