TUN 
as they call it, fat quarter, and hinders her 
steering, by keeping the water from passing 
swiftly to her rudder ; and if this trussing 
lie too high above the water, she wilt want 
bearing for her works behind, unless her 
quarter be very well laid out 
TUFA, in mineralogy, is calcareous, and 
of a yellowish-grey colour. It occurs sojid, 
blit generally porous, and marked with im- 
pressions of reeds, moss, and other vegeta- 
bles; it is soft, easily frangible, and not 
much heavier tlian water : it elfervesces 
with acids, and is little else than carbonate 
of lime. The more compact kinds are em- 
ployed in building. 
TULBAGIA, in botany, a genus of the 
Hexandria Monogynia class and order. 
Natural order of Spathaceae. Narcissi, Jus- 
sieu. Essential character: corolla funnel- 
form, with a six-cleft border ; nectary 
crowning the aperture, three-leaved ; leaf- 
lets bifid, the size of the border ; capsule 
superior. There are two species; viz. T. 
alliacea, narcissus-leaved tulbagia; and T. 
cepacea : both natives of the Cape of Good 
Hope. 
TULIPA, in botany, tulip, a genus of 
the Hexandria Monogynia class and order. 
Natural order of Coronarias. Lilia, Jussieu. 
Essential character : corolla six-petalled, bell- 
shaped ; style none. There are five species. 
TUN, or Ton, originally signifies a large 
vessel or cask of an oblong form, biggest in 
the middle, and diminishing towards its two 
ends, girt about with hoops, and used for 
stowing several kinds of merchandize, for 
convenience of carriage ; as brandy, oil, 
sugar, skins, hats, &c. This word is also 
used for certain vessels of extraordinary 
bigness, serving to keep wine in for several 
years. 
Tun is also a certain measure for liquids ; 
as wine, oil, &c. See Measure. , 
Tun is also a certain weight whereby the 
burden of ships, &c. are estimated. 
TUNE, or Tone, in music, is that pro- 
perty of sounds by which they come under 
the relation of acute and grave. If two or 
more sounds be compared together in this 
relation, they are either equal or unequal 
in the degree of tune ; such as are equal, 
are called unisons ; the unequal constitute 
what are called intervals, which are the 
ditferenees of tone between sounds. Sono- 
rous bodies are found to differ in tone : 1st. 
According to the different kinds of matter ; 
thus the sound of a piece of gold, is much 
graver than that of a piece of silver of the 
same shape and dimensions. 2d. Accord- 
TUN 
ing to the different quantities of the same 
matter in bodies of the same figure ; as a 
solid sphere of brass, of one foot diameter, 
sounds acuter than a sphere of brass of two 
feet diameter. But the measures of tone 
are only to be sought in the relations of the 
motions that are the cause of sound, which 
are most discernible in the vibration of 
chords. Now, in general, we find that in 
two chords, all things being equal except- 
ing the tension', the thickness, or the length, 
the tones are different; which difference 
can only be in the velocity of their vibra- 
tory motions, by which they perform a dif- 
ferent number of vibrations in the same 
time ; as it is known that all the small vi- 
brations of the same chord are performed 
in equal times. Now the frequenter or 
quicker those vibrations are, the more acute 
is the tone ; and the slower and fewer they 
are in the same space of time, by so much 
the more grave is the tone. So that any 
given note of a tune is made by one certain 
measure of velocity of vibrations, that is, 
such a certain number of vibrations of a 
chord or string, in such a certain space of 
time, constitutes a determinate tone. 
TUNGSTATE. See Tungstic acid. 
TUNGSTEN, in mineralogy, is usually 
of a yellowish and greyish white ; it occurs 
massive, disseminated, and very frequently 
crystallized ; it sometimes occurs in large, 
coarse, and small granular distinct concre- 
tions, with streaked and shining surfaces. Its 
specific gravity is from 4.3 to 6. It is in- 
fusible, without addition, before the blow- 
pipe. It melts with borax, but scarcely 
changes its colour. When pulverized and 
digested with nitrous or muriatic acid, it 
leaves a yellow residue which is the oxide 
of tungsten. The mineral contains, ac- 
cording to Scheele, 
Yellow oxide of tungsten... 65 
Lime Si. 
Silica 4 
100 
This specimen was obtained in Sweden : a 
specimen from Cornwall analyzed by Klap- 
roth yielded 
Yellow oxide of tungsten .. 75.25 
Lime '. is.ro 
Oxide of iron 1.25 
manganese 0.75 
Silica 1.50 
97.45 
Loss 2.55 
100 
