Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 13, MAT-MIC

730 M E T E 0
.Weather;. and then was obferved to cbntraa itfelf again, and fud-
^ denly difappear. In lefs than a minute, however, it
would become vifible as before, and run along from one
place to another ; or would expand itfelf over more
tnan three acres of the adjacent mountains. The atmo-
fphere at this time was thick and hazy.
All thefe luminous appearances are probably owing
to the extrication of hydrogen gas fo llightly impreg¬
nated with phofphorus as to continue emitting a faint
light, without producing that brilliant flalh which
follow s the fudden extrication into the air, of the com¬
mon phofphorated hydrogen gas obtained in the ufual
chemical experiment of throwing phofphuret of lime
into water.
Chap. VI. Of the Application of Meteorology to
Prognojlicating the Weather.
Ir has ever been a principal object among mankind,
to fore tel the changes of weather that are likely to fol¬
low particular appearances in the Iky, among the
heavenly bodies, &c.; and it has been often alleged,
that in this refpeft the philofopher is far behind the
hulbandman and the Ihepherd. Were the former, how¬
ever, to add to his fcientific refearches the obfervations
to w Inch the latter are indebted for their judgment of
the weather, he would foon be far fupericr to them in
*79 this refpeft.
Kirwan s Dr Kirwan has lately endeavoured to difcover pro-
®n the vvea-ra^e rides ^or Prognofticating the weather in different
than lealons, as far as regards this climate, from tables of
obfervation alone j and from comparing a number of
thefe obfervations made in England, from 1677 to 1789,
he found,
1. I hat when there has been no ftorm before or after
the vernal equinox, the enfuing fummer is generally
dry, at lead five times in fix.
That when a ftorm happens from an eafterly
point, either on the 19th, 20th, or 21ft of May,
the fucceeding fummer is generally dry four times in
five.
3. That when a ftorm arifes on the 26th, 27th, or
29th of May (and not before), in any point, the fuc¬
ceeding fummer is generally dry four times in five.
4. If there be a ftorm at fouth-weft or weft-fouth-
weft on the 19th, 20th, 21ft, or 2 2d of March, the
fucceeding fummer is generally wet five times in fix.
In this country winters and fprings, if dry, are rnofl
commonly cold ; if moift, warm : on the contrary, dry
fummers and autumns are ufually hot, and moift fummers
cold. So that if we know the moiftnels or drynefs of
a feafon, we can judge pretty accurately of its tempera¬
ture. r
from a table of the weather kept by Dr Rutty, in
Dublin, for 41 years, Dr Kirwan endeavoured to cal¬
culate the probabilities of particular feafons being fol¬
lowed by others. I hough his rules relate chiefly to
the climate of Ireland, yet as probably there is not
much difference between that ifland and Britain, in the
general appearance of.the feafons, v/e ftiall mention his
conclufions here.
In 41 years there were fix wet fprings, 22 dry, and
13 variable; 20 wet fummers, 16 dry, and five varia-
3
R ° L 0 G Y. chap. VI
ble ; 11 wet autumns, 11 dry, and 19 variable. A Weather
ieaion according to Dr Kirwan, is counted wet, when ' v—^
it contains two wet months. In general, the quantity
of ram which falls in dry feafons is left than five inches *
m wet feafons more. Variable feafons are thofe in which
there falls between 30 and 36 pounds, a pound being-
equal to .157637 of an inch. & g i
1 he order in which the different feafons fucceeded Probable
each other, was as in the following table. fafceflioa
of feafons,
A dry fpring
A wet fpring
A variable fpring
A dry fummer
A v-et fummer
A variable fummer
A dry fpring and dry \ p;
fummer 1 ^
L c
A dry fpring and w-et f
fummer , ^
A w!et fpring and dry C
fummer 1
A vret fpring and vret
fummer
1
1
{
1
1
1
{:
-O
"C
u
£
A wet fpring and va¬
riable fummer
A dry fpring and va
riable fummer
A variable fpring and
dry fummer
A variable fpringand
wet fummer
{
1
{
1
{
A variable fpring and C
variable fummer l
C dry
wet
variable
dry
wet
variable ^ £
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
| wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
dry
wet
variable
Time:
. S
c
11
8
3
o
.5
1
5
7
1
5
5
6
5
3
12
1
3
1
3
4
4
2
o
6
o
o
o
2
1
2
1
O
o
o
2
1
2
O
2
I
I
5
o
1
o
Proba
bility
8
T-g-
5
TT
1
tt
IT
J>
1 o
J
■s
6
ITS
S
To"
3
To-
1 z
Vo-
I
T
3
T
O
TT
O
. Hence Dr Kirwan deduced the probability of the Buie! for
kind of feafons which would follow others. This pro-Pro§noft!'
bability is expreffed in the laft column of the table, and catinf th*
is to be underftood in this manner. The probabilityWe&
that