GAG 
GAL 
the force of the wind upon any given surface. 
It was invented by Dr. Lind, who gives the 
following description ol it, Phil. Irans. yol. 
lvv This instrument consists of’ two glass 
tubes. Art, CD, Plate Miscel fig. 98. of 
five or six inches in length. 1 heifi bores, 
which are so much the better for being equal, 
are about four-tenths of an inch in diameter. 
They are connected together like a siphon, 
by a small bent glass-tube marked a b, the 
bore of which is about one-tenth of an inch 
in diameter. On the upper end ot the leg 
A rt there is a tube of latten biass, which is 
kneed or bent perpendicularly outwards, and 
lias its mouth open towards F. On the othei 
le<* CD is a cover with a round hole G in 
the upper part of it, two-tenths of an inch in 
diameter. This cover and the kneed tube 
are connected together by a slip of brass c d, 
which not only gives strength to the whole 
instrument, but also serves to hold the scale 
Hi. The kneed tube and cover are fixed 
on with 'hard cement or sealing-wax. lo 
the same tube is soldered a piece of lu ass c, 
with a round hole in it to receive the steel 
spindle KL; and at/ there is just such ano- 
ther piece of brass soldered to the brass-hoop 
<r which surrounds, botli legs ot the instru- 
ment. There is a small shoulder on the 
spindle at f, upon which the instrument rests, 
and a small nut at i, to prevent it fiom being 
blown off the spindle by the wind, the 
whole instrument is easily turned round upon 
the spindle by the wind, so as always to pre- 
scut the mouth of the kneed tube towauis it. 
The end of the spindle has a screw on it, 
by which it may be screwed into the top of 
a post or a stand made on pm pose. It has 
also a hole at L, to admit a smail icv._i lot 
screwing it into wood with more readiness 
and facility. A thin plate of brass ft is_ sol- 
dered to the kneed tube, about halt an inch 
above the round hole G,. so as to prevent 
rain from falling into it. There is likewise a 
crooked tube A 13, fig. 99. to be put oc- 
casionally upon the mouth of the kneed tube 
F in order to prevent rain from being blown 
into the mouth of the wind-gage when it is 
left out all night or exposed in the time of 
rain. . , 
The force or momentum of the v incl may 
be ascertained by the assistance of this in- 
strument, by filling the tubes halt full of 
water, and pushing the scale a little up oi 
down, till the 0 of the scale, when the in- 
strument is held up perpendicularly, be on a 
line with the surface of the water in both 
legs of the wind-gage. The instrument being 
thus adjusted, hold it up perpendicularly, 
and, turning the mouth of the kneed tube to- 
wards the wind, observe how much the wa- 
ter is depressed by it in the one leg, and 
raised in the other. The sum of the two is 
the height of a column of water which the 
wind is 3 capable of sustaining at that time ; 
and every body that is opposed to that wind 
will be pressed upon by a force equal to the 
weight of a column of water, having its base 
equal to the altitude of a column ol water , 
sustained by the wind in the wind-gage. 
Hence the force of the wind upon any body 
where the surface opposed to it is known may 
be easily found ; and a ready comparison 
may be made betwixt the strength of one 
sale of wind and that ot another. 
° The force of the wind may be likewise 
measured vyith this instrument, by filling it 
G AG 
until the water runs out at the hole G. For 
if we then hold it up to the wind as before, a 
quantity of water will, be blown out ; and if 
both legs of the instrument are of the same 
bore, the height of the column sustained 
will be equal to double the column of water 
in either leg, or the sum of what is wanting 
in both legs. But if the legs are of unequal 
bores, neither of these will give the true 
height of the column of water which the 
wind sustained. But the true height may be 
obtained by the following formula;. 
Suppose that after a gale of wind which had 
blown the water from A to B, fig. 100, forcing 
it at the same time through the other tube out 
at E. the surface of the water should be found 
standing at some level as DG, and it were re- 
quired to know what was the height of the co- 
lumn EF or AB, which the wind sustained. In 
order to obtain this, it is only necessary to find 
the height of the columns DB or GF, which are 
constantly equal to one another; for either of j 
these, added to one of the equal columns AD, i 
EG, will give the true height of the column of j 
water which the wind sustained. 1. Let the j 
diameters AC, EH, of the tubes, be respectively 
represented by cd; and let a = AD or EG, and 
x — DB or GF ; then it is evident, that the co- 
lumn DB is to the column EG, as dx to d 2 a. 
But these columns are equal. Therefore d x — 
d'a 
d 2 a ; and consequently x — — . 2. But if, at 
I any instant of time whilst the wind was blow- 
ing, it was observed, that when the water stood ; 
at E, the top of the tube out of which it is I 
forced, it was depressed in the other to some 
| given level BE, the altitude at which it would ■ 
| have stood in each had it immediately subsided, J 
! may be found in the following manner. Let b j 
i =: AB or EF. Then it is evident that the co- j 
lumn DB is equal to the difference of columns' 
EF, GF. But the difference of these columns is 
I d b 1 
as d 2 b — d 2 x ; and consequently x = 
c — f— a I 
For the cases when the wind blows in at the ! 
1 narrow leg of the instrument : Let AB = EF 
I = b, EG or AD = a, GF = DB = *, and the 
diameters EH, GA, respectively = d, c as be- 
J fore. Then it is evident, that the column AD ; 
i is to the column GF as ad to d l x. But these co- 
lumns are equal ; therefore d 2 x — ac 2 ; and con- 
sequently .v — It is also evident, that the 
column AD is equal to the difference of the co- j 
lumns AB, DB ; but the difference of these co- 
lumns is as be 1 — c 2 x. Therefore d 2 x = be 2 — dx. 
, hc " 
Whence we get x — ,, , - 2 -. 
d A -j- d 
The use of the small tube of communica- 
tion a b, fig. 98. is to check the undulation 
of the water, so that the height of it may be 
read off from the scale with ease and cer- 
tainty. But it is particularly designed to j 
prevent the water from being thrown up to j 
a much greater or less altitude, than the true 
height of the column which the wind is able j 
at that time to sustain, from its receiving a 
sudden impulse whilst it is vibrating either in 
its ascent or descent. As in some cases fresh 
water hi this instrument might be liable, to 
freeze, and thus break the tubes, Dr. Lind 
recommends a saturated solution of sea-salt 
to be used instead of it, which does not freeze 
till Fahrenheit’s thermometer falls to 0. 
Tide- Gage, an instrument used for de- 
termining the height of the tides by Mr. 
Bayley, in the course of a voyage towards 
the south pole, &c. in the Resolution and Ad- 
venture, in the years 1772, 1773, 1774, and 
GAL 79-' 
1775. This instrument consists of a glass 
tube, whose internal diameter was 7-iOths 
of an inch, lashed fast to a 10 foot fir rod, di- 
vided into feet, inches, and parts; the rod 
being fastened to a strong post fixed firm 
and upright in the water. At the lower end 
of the tube was an exceedingly smail aper- 
ture, through which the water was admitted. 
In consequence of this construction, the sur- 
face of the water in the tube was so little af- 
fected by the agitation of the sea, that its 
height was not altered the 10th part of an 
inch when the swell of the sea was 2 feet ; 
and Mr. Bayley was certain, that with this 
instrument he could discern a difference of 
the Kith of an inch in the height of the tide. 
GAHNIA, a genus of the monogynia 
order, in the hexandria class of plants. The 
calyx is an involucrum with two or live flow- 
ers ; the corolla is two-valved ; the stamina 
six capillary and very short filaments ; the 
anther* linear, sharp-pointed at the apex, 
and as long as the corolla ; there is no peri- 
carpium: the seed is single and oblong. 
There are two species, herbs of New Zea- 
land and Otaheite. 
GAIAN1TES, gainaitce, in church his- 
tory, a branch of eutychians. 
GALBULA, in ornithology, a genus of 
•the order pica;, bill straight, very long, quad- 
rangular, pointed; nostrils oval, at the base 
of the bill ; tongue short, sharp-pointed ; 
thighs downy on the forepart. The viridis 
inhabits the moist woods of Guinea and Bra- 
zil ; the size of a lark : it feeds on insects. 
There are three other species, viz. the grau- 
dis, the paradisca, anil albirostris. 
GALANGALS, the name of two roofs 
kept in the shops, a greater and a smaller; 
of which the smaller is by far most esteemed, 
bee Materia Medica. 
GALANTHUS, The Snow-drop, a ge- 
nus of the monogynia order, in the hex- 
andria class of plants, and in the natural 
method ranking under the ninth order, spa- 
thaceie. There are three concave petals ; 
and the nectarium consists of three small 
emarginated petals ; the stigma is simple. 
There is but one species, viz. the nivalis ; 
which is a bulbous rooted flowery perennial, 
rising but a few inches in height, and adorn- 
ed at top with small tripetalous-flowers of a 
white colour. There are three varieties, 
viz. the common single-flowered snow-drop, 
the semi double snow-drop, and the double 
snow-drop, They are beautiful little plants,, 
and are much valued on account of their 
early appearance, often adorning the gardens 
in January or February, when scarcely any 
other flower is to be seen, and continue very 
often till the beginning of March, making a 
very ornamental appearance, especially when 
disposed in clusters towards the fronts of the 
borders, &c. The single kind comes first 
into bloom, then the semi-double, and after 
that the double. They will succeed any 
where, and multiply exceedingly by off-sets 
from the roots. 
GALARDIA, a genus of the class and 
order syngenesia polygamia frustranea. The 
recept. is chaffy ; seed crowned with five- 
leaved calycle ; cal. two-rows of scales, al- 
most equal. There is one species ; an annual 
of Louisiana. 
GALAX, a geuus of the pentandria mo- 
nogynia class and order. The cal. is ten- 
