GLA 
GLA 
century of the Christian sera, but it did not 
come into common use till very long after 
^his. 
Glass, painting on. See Enamelling. 
Glass, in sea affairs, the usual appella- 
tion for a telescope. A night-glass is a te- 
lescope made for viewing objects at night. 
Halt-hour glass, called also the watch-glass, 
is used to measure the time which each 
watch has to stay upon deck. Half and 
quarter-minute glasses' are used to ascertain 
the rate of the ship’s velocity, measured by 
the log ; these glasses should be frequently 
compared with a good stop-watch, to deter- 
mine exactly how many seconds they run. 
GLAUBER (John Rudolph), an in- 
dustrious chemist, was born in Germany. 
After passing a considerable time in travel, 
hejsettled at Amsterdam, about the middle 
of the seventeenth century. He wrote a 
number of works, mostly infected with the 
enigmatical jargon and unintelligible theory 
of the hermetic philosophy, yet containing 
some useful facts in true chemistry, and 
some processes of his own invention. His 
name is perpetuated in the purgative neu- 
tral salt called Glauber’s, composed of 
the sulphurc acid and soda ; a valuable 
remedy, but, together with others of his 
invention, extolled by himself to an ex- 
travagant degree. He kept several of his 
medicines secret, and made advantage of 
them as nostrums. Of his works an abridged 
collection was made in German, which was 
translated into English in 1689 ; but they 
are now consigned to oblivion. 
Glauber’s salt. See Soda, sulphate 
of. It is found native ; and, according to 
Bergman, it contains sulphuric acid, soda, 
and water, in the proportions of 27.15,58; 
that is, when saturated with water of cry- 
stallization. When efflorescent, the native 
Glauber’s salt contains, beside pure sul- 
phate of soda, some oxide of iron, and por- 
tions of muriate and carbonate of soda. It 
is found in old salt-mines, on the borders of 
the salt lakes in different parts of the world, 
and on the surface of peat-mosses in France. 
It is also held in solution in the Natron- 
lakes of Egypt, and the mineral springs of 
Carlsbad. Glauber's salt easily dissolves in 
water, and shoots into long and beautiful 
crystals, which contain a large quantity of 
water ; in consequence of which they un- 
dergo the aqueous fusion, when exposed to 
heat. This salt, oh account of its efficacy 
as a purgative, was formerly held in the 
highest esteem, and was denominated sal 
inirabile Glauberi. It has been used in 
VOL. III. 
some countries as a substitute for soda, In 
the manufacture of white glass. 
GLAUCQPIS, or the wattle-bird, in na- 
tural history, a genus of birds of the order 
Pic*. Generic character : bill incurvate 
and arched ; lower mandible shorter than 
the upper, and caruneulate beneath at the 
base; nostrils depressed, half covered with 
a cartilaginous membrane ; tongue cartila- 
ginous, split and ciliated at the end ; legs 
carinated at the back ; feet formed for 
walking. 
The G. cinerea, or cinereous wattle-bird, 
is about the size of a jay ; it is found in 
every part of New Zealand: berries, and 
insects of almost every kind, constitute its 
food ; it rarely perches on trees ; but is of- 
ten seen walking on the ground ; its notes 
are said at different times to resemble 
whistlings and murmurings, and its flesh is , 
good for the table. 
GLAUX, in botany, a genus of the Pen- 
tandria Monogynia class and order. Natu- 
ral order of Calycanthem*. Salicari*, Jus- 
sieu. Essential character: calyx one-leaf- 
ed, bell-shaped ; corolla none ; capsule one- 
celled, five-valved, five-seeded. There is 
only one species, viz. G. maritima, sea milk- 
wort, or black salt wort. It is common on 
the sea-coast, and on salt marshes at a dis- 
tance from the sea ; it is a beautiful little 
plant, enlivening large tracts of the dreary 
situations where it is found ; the whole plant 
is succulent, and salt to the taste. 
GLAZIN G, in the arts, is the polishing 
or crusting over earthen ware. When 
earthen ware is properly baked, it is dipped 
into a composition called a glaze, made by 
mixing together in water, till it becomes as 
thick as cream ; fifty-six parts of white lead, 
twelve of ground flints, and three of ground 
flint glass. The ware, by being baked, ac- 
quires a strong property of imbibing 
moisture, and in this state, it is called bis- 
cuit; when dipped into the glaze, it at- 
tracts it into its pores, and the ware be- 
comes presently dry ; it is then exposed a 
second time to the fire, by which means 
the glaze it has imbibed is melted, and a 
thin, glassy coat is formed upon the surface. 
The colour is more or less yellow, accord- 
ing as a greater or less proportion of lead 
has been used. The lead promotes also the 
vitrification ; the flint serves to give a con- 
sistency to the lead during the time of its 
vitrification, and to prevent its becoming 
too fluid, and running down the sides of 
the ware, and thereby leaving them un- 
glazed. This kind of glazing by lead, is 
Z 
