BAR 
as well as the alteration of the wind during heavy rains in 
this country, can only be properly accounted for. 
Mr. Copland’s fourth aphorifm is, ‘That the heavieft 
rains, when of long continuance, generally begin with 
the wind blow ing eafterly, when it gradually veers round 
to the fouth ; and that the rain does not then begin to 
ceafe till the wind has got to the wed, or rather a little to 
the northward of it, when, it may be added, it commonly 
blows with fome violence.’ For farther obfervations on 
the weather, and other fubjedts connected with the baro¬ 
meter, fee the article Weather. 
Of the Barometer in Measuring Altitudes. 
The fecondary character of the barometer, namely, as 
an inftrument for meafuring accelTible heights or depths, 
was fird propofed by Pafcal, and Defcartes, and fucceed- 
ing philofophers have been at great pains to afcertain the 
proportion between the fall of the barometer and the 
height to which it is carried; as Halley, Mariotte, Ma- 
raldi, Scheuchzer, J. Calfani, D. Bernoulli, Horrebow, 
Bougeur, Shuckburgh, Roy, and more efpecially De Luc, 
who has given a critical and hidorical detail of mod of the 
attempts that have at different times been made for ap¬ 
plying the motion of the mercury in the barometer to the 
meafurement of accellible heights. And for this purpofe 
ferves the portable barometer above defcribed, which 
ffiould be made with all the accuracy pofiible. Various 
rules have been given by the w-riters on this fubjeft, for 
computing the height afcended from the given fall of 
the mercury in the tube of the barometer, the moll accu¬ 
rate of which was that of Dr. Halley, till it was rendered 
much more accurate by the indefatigable refearches of De 
Luc, by introducing into it the corrections of the columns 
of mercury and air, on account of heat. And other cor¬ 
rections and modifications of the fame may be feen under 
the article Atmosphere, where the mod correct rule is 
deduced from one fingle experiment only. This rule is 
as follows : 
The rule for computing altitudes, is this, viz. 10,000 X 
M . 
log. of — is the altitude in fathoms, in the mean tempe- 
m 
rature of 31 0 ; and for every degree of the thermometer 
above that, the refult mud be increafed by fo many times 
its 435th part, and diminilhed when below' it: in which 
theorem M denotes the length of the column of mercury 
in the barometer tube at the botton, and m that at the top 
of the hill, or other eminence ; which lengths may be ex- 
prefled in any one of the fame fort of meafures, whether 
feet, or inches, or tenths, See. and either Englidi, or 
French, or of any other nation ; but the refult is always 
in fathoms, of fix Englilh feet each. And the precepts , 
in words, for the practice of meafurements by the baro¬ 
meter, are thefe following : id. Obferve the height of 
the barometer at the bottom of any height or depth, pro¬ 
pofed to be meafured 3 together with the temperature of 
tlte mercury by means of the thermometer attached to the 
barometer, and alfo the temperature of the air in the ffiade 
by another thermometer which is detached from the ba¬ 
rometer. adly, Let the fame thing be done at the top of 
the faid height or depth, and as near to the fame time with 
the former as may be. And let thofe altitudes of mercury 
be reduced to the fame temperature, if it be thought ne- 
eeffary, by correCling either the one or the other, viz. 
augmenting the height of the mercury in the colder tem¬ 
perature, or diminifhing that in the warmer, by its 9600th 
part for every degree of difference between the two ; and 
the altitudes of mercury fo corrected, are what are denot¬ 
ed by M and m in the algebraic formula above. 3dly, 
Take out the common logarithms of the two heights of 
mercury, fo corrected, and fubtraCt the lefs from the 
greater, cutting oft from the right-hand fide of the re¬ 
mainder three places for decimals; fo ihall thofe on the 
left be fathoms in whole numbers, the tables of logarithms 
being underftood to be fuch as have feven places of deci¬ 
mals. 4thly, Correct the number laff found, for the dif- 
Vql. II. No. 100. 
BAR 74 r 
ference of the temperature of the air, as follows: viz. 
Take half the fum of the two temperatures of the air, 
fhewn by the detached thermometers, for the mean one ; 
and for every degree which this differs from the ftandard 
temperature of 31°, take fo many times the 435th part of 
the fathoms above found, and add them if the mean tem¬ 
perature be more than 31°, but fubtraCt them if it be be¬ 
low 31 0 ; fo fliall the fum or difference be the true alti¬ 
tude in fathoms, or, being multiplied by 6, it will give the 
true altitude in Englifli feet. 
Ex. 1. Let the ffate of the barometers and thermometers 
be as follows, to find the altitude, viz. 
Thermometers. 
Barometers. 
detached. 
attached. 
57 
57 
29-68 lower. 
42 
43 
25-28 upper. 
mean 494 
dif. 14 
As 9600 : 14 ;; 29-68 ; -04 
cor -04 logs. 
mean 49^ M=2 9 -64 - 4718782 
ffand.3t vi— 25-28 - 4027771 
dif. i8£ 
As 435 : i 84 :: 691-ox 1 : 29-385- 
29-388 
the altitude/ 720-399 fath. 
fought is \ or 4322-394 feet. 
Ex. 2. To find the altitude of a hill, when the'ffate of 
the barometer and thermometer, as obferved at the bot¬ 
tom and top of it, is as follows, viz. 
Thermometers. 
Barometers. 
detached. 
attached. 
35 
41 
29 A 5 
3 i 
3 * 
26 ’82 
mean 33 
dif. 3 
As 9600 
3 
; 29-45 : -01 
•01 logs. 
mean 33 M=29'44 - 4S8937S 
ffand. 31 m— 26-82 - 4284583 
dif. 2 As 435 : 2 :: 404-790 : i-8S 
i-86 
the altitude f 406-65 fathoms, 
fought is \ or 2439-90 feet. 
See this rule mveffigated at the end of the article Pneu¬ 
matics. And let it be obferved, that the mean height 
of the barometer in London, upon an average of two ob¬ 
fervations in every day of the year, kept at the houfe of 
the Royal Society, for many years paff, is 29-88 ; the me¬ 
dium temperature, or height of the thermometer, accord¬ 
ing to the fame, being 58°. But the medium height at 
the furface of the fea, according to Sir Geo. Shuckburgh 
(Philof. Tranf. 1777, p.586), is 30-04 inches, the heat of 
the barometer being 55 0 , and of the air 62°. 
B AROME'TRIC AL, adj. Relating to the barometer. 
—He is very accurate in making barometrical and thermo- 
metrical inftruments. Derham. 
B AROMET'Z,yi in botany. See Polypodium. 
BA'RON,yi \_baron, Fr. perhaps of beorn , Sax. noble. 
The origin and primary import of this term is much con- 
tefted. Menage derives it from the Latin baro, which we- 
find ufed in the pure age of that language for vir, a ‘ftout 
or valiant man whence, according to this author, it was, 
that thofe placed next the king in battles were called 6 a- 
rones, as being the braved men in the army and, as prin¬ 
ces frequently rewarded the bravery and fidelity of thofe 
about them with fees, the word came to be iifed for any 
noble perfon who holds a fee immediately of the king. 
Iiidore, and after him Camden, take the word, in its ori¬ 
ginal fenfe, to fignify a ‘mercenary foldier.’ Meffieursof 
the Port Royal derive it from ffagoi;, Gr. weight or autho¬ 
rity. Cicero ufes the word baro for a ftupid brutal man; 
9 C and 
