THE 
changes of heat, &c. to the eye ; and the latter an 
inftrument that meafures thofe changes •, on which 
foundation the thermometer fir quid be a more accu- 
rate Thermofcope. 
This difference the excellent Wolfius taking hold of, 
defcribes all the thermometers in ufe as Thermofcopes; 
{hewing, that none of them do properly meafure the 
changes of heat, dec. and that none of them do more 
than indicate the fame. 
Though their different heights, yefterday and to-day, 
fhew a difference of heat ; yet fince they do not dif- 
cover the ratio of yefterday’s heat to to-day’s, they 
are not ftricftly thermometers. 
The Adda Erud. Lipf. propofes a method of gradu- 
ating the common thermometers fo, as that the une- 
qual divifions thereof fhall correfpond to equal de- 
grees of heat, whereby the ratio of to-day’s heat to 
yefterday’s will be meafured, and confequently the 
Thermofcope improved into a thermometer. 
The method is thus : 
Take a flender tube about four palms long, with a 
ball fattened to the fame •, pour into it fpirit of wine, 
enough juft to fill the ball when furrounded with ice, 
and not a drop over ; in this ftate feal the orifice of 
the tube hermetically, and provide fix veffels, each 
capable of containing a pound of water, and fome- 
what over; and in the firft pour eleven ounces of 
warm water, into the fecond ten ounces, into the 
third nine, &c. 
This done, immerge the thermometer into the firft 
veffel, and pour into it one ounce of hot water, ob- 
ferving how high the fpirit rifes in the tube, and noting 
the point with an unit, then remove the thermometer 
into the fecond veffel, into which are poured two 
ounces of hot water, and note the place the fpirit rifes 
to with two ; by thus proceeding till the whole pound 
of water is fpent, the inftrument will be found to be 
divided into twelve parts, denoting fo many terms or 
degrees of heat; fo that at two, the heat is double 
to that of one ; at three triple, &c. 
But Wolfius fhews, that though this method is plau- 
fible, yet it is deceitful, and built upon falfe fuppo- 
fitions ; for it takes for granted, we have one degree 
of heat, by adding one ounce of hot to eleven of cold 
water, two degrees by adding two ounces to ten, &c. 
It fuppofes that a fingle degree of heat afts on the 
fpirit in the ball of a fingle force, a double with a 
double force, &c. 
Laftly, it fuppofes, that if the effed be produced in 
the thermometer, by the heat of the ambient air, 
which is here produced by the hot water, the air has 
the fame degree of heat with the water. 
But none of thefe fuppofitions are true ; for as to the 
firft, allowing the heat of the hot water equally diftri- 
buted through the cold, one degree of heat will be 
diftributed through eleven parts, two through ten, 
three through nine, &c. taking therefore equal bulks 
of water, e. g. a twelfth part of each, the heat will 
not be double in the one, triple in another, &c. 
The firft fuppolition is therefore erroneous, and fo 
is the fecond ; neither is the heat of the hot water 
equally diffbied through the cold ; nor does the heat 
of the hot water ad uniformly on the fpirit of wine ; 
i. e. not with the fame force all the time of its action. 
For the third fuppofition ; the heat of the ambient air 
ads not only on the fpirit of wine on the ball, but 
alfo on that in the tube ; and therefore this, as well 
as that, fhould be changed. 
Dr. Hook, in order to adjuft the gradations of a ther- 
mometer with the greater accuracy, hath contrived 
and defcribed an inftrument for that purpofe, in his 
Micrographia, p. 38. 
The way of filling Thermofcopes , or fuch other fmall glafs 
tubes, with fpirit of wine or water. 
Take the ball of the glafs, and then warm it gently 
between your hands ; then heat it very well (though 
.gently) before a good fire, turning it round, that it 
may be equally warm ; for, without this caution 
f 
THE 
there will be danger of its breaking : then applying 
the ball to the flame of a lamp or candle, burning it 
about in it, heat it as hot as you can, without melt- 
ing the glafs ; and then fpeedily imroerfmg the open 
end of the pipe into the veffel of liquor that you in- 
tend to fill it withal, the liquor will rife into it, and 
fill it near full. 
The reafon of which afcent of the liquor is, that the 
air within the ball and the tubes being expelled in 
great meafure by the heat, or at leaft rarefied there 
to a very great degree, the immerfed open end of the 
tube keeps off the preffure of the circumambient at- 
mofphere on that part of the liquor that the end of 
the tube covers : but the atmoiphere preffes on all 
other parts of the liquor in the open veffel ; and, 
confequently, there being none, or a very fmall 
quantity of air within the tube to hinder it, forces it 
by its weight up into the tube, till it gain an equili- 
brium with the preffure or weight of the air without. 
If the tube cannot be filled full enough by this me- 
thod, the reft may be fupplied by a fmall glafs fun- 
nel ; the fhank of which muft be drawn out exceed- 
ing flender, and inferted into the orifice of the tube ; 
and then, by blowing, you may force by your breath 
the fpirit of wine into the tube, fo as to fill it quite, 
or to what degree you pleafe. 
Dr. Hook, in his Micrographia, hath an engine for 
graduating his thermometers, to make them true 
ftandards of heat and cold. 
The thermometers or Thermofcopes are inftrumgnts 
of very great ufe to gardeners in the management of 
ftoves. They fhew by inipeeftion the prefent condi- 
tion of the air, and whether it be hot or cold ; which 
day in fummer is the hotteft, and in the winter which 
is the coldeft, or any part of the day ; and from 
thence many ufeful experiments have and may be 
made ; viz. how much one fpring exceeds another in 
coldnefs ; which baths are the hotteft or coldeft ; and, 
if being held in the hand of a perfon in a fever, or 
otherwife applied, will nicely Ihew the abatement or 
increafe of a fever. 
The common thermometer which is ufed for hot- 
houfes, has a long tube of about two feet in length, 
and is about the eighth part of an inch diameter ; and 
in this it is remarked, that the air is cold for the 
plants when the fpirit rifes to fifteen inches ; that it 
is temperate at fixteen inches and a half ; that it is 
warm when it rifes to eighteen inches ; and this is 
the ftandard for Pine apple heat. It is marked for 
hot air at twenty inches, and fultry hot at twenty- 
one and a half ; but in the common thermometers, 
thefe degrees are differently marked ; this temperate 
air is about our warm, this warm air our hot, and our 
hot air is about the fame as the fultry. 
Thefe thermometers are marked with fome offthe 
names of the moft remarkable plants which are preferv- 
ed in the hot-houfes ; but as the number of thefe plants 
has been greatly increased in England of late years, I 
have direded fome thermometers to be made with a 
fcale divided into degrees, and with three different 
points of heat marked in claffes, which correfpond 
with thefe thermometers ; and under each clafs I have 
drawn up lifts of the feveral plants, ranged according 
to the degrees of heat in which they are found to ftic- 
ceed ; whereby the culture of them is made eafy to 
perfons of fmall fkill. 
By this means every gardener may know when it is 
proper to apply his heat in its full force, and what 
degree of heat ought to be ufed for the welfare of any 
plant from any part of the world. 
Mr. Patrick has fixed his thermometer to a fcale of 
ninety degrees, which are numbered from the top 
downwards, and alfo a moveable index fitted to it. 
The defign of this is to fhew how the heat or cold is 
changed, from the time it was laft looked upon, ac- 
cording to the different degrees of heat and cold in 
all latitudes ; as by the trial of two thermometers 
that have been regulated abroad, the one by Dr. 
Halley, in his late fouthern voyage, and the other by 
Capt. Johnfon, in his voyage to Greenland, The 
1 3 E firft 
