a

Letter, than the other. However, this makes no odds as to LEVANT, in geography, signifies any country Levane
Lettuce.
the kind of style; for every one would choose to speak situated to the east of us, or in the eastern side of any

Leucata.
as correctly as he writes, if he could. And there. continent or country, or that on which the sun rises.
fore all such words and expressions, as are unbecom- LEVANT, is also a name given to the eastern part
ing in conversation, should be avoided in letters ; and of the Mediterranean sea, bounded by Natolia or the
a manly fimplicity free of all affectation, plain, but Lesser Asia on the north, by Syria and Palestine on
decent and agreeable, should run through the whole. the east, by Egypt and Barca on the south, and by
This is the usual style of Cicero's epistles, in which the island of Candia and the other part of the Medi-
the plainness and fimplicity of his diction is accom- terranean on the west.
panied with something so pleasant and engaging, that LEVATOR, in anatomy, a name given to several
he keeps up the attention of his reader, without fuf- muscles. See Anatomy, Table of the Muscles

. .
fering him to tire. On the other hand, Pliny's style LEUCA, in antiquity, a geographical measure of
is succinct and witty ; but generally fo full of turns length in use among the later Gauls; which, accord-
and quibbles upon the found of words, as apparently ing to Jornandes, who calls it leuga, contained fif-
render it more ftiff and affected than agrees with teen hundred paces, or one mile and a half. Hence
conversation, or than a man of sense would choose in the name of league, now reckoned at three miles ; in
discourse, were it in his power. You may in fome the lower age, called leuva.
measure judge of Pliny's manner, by one sort letter LEUCADENDRON, in botany: A genus of the
to his friend, which runs thus : “ How fare you? monogynia order, belonging to the tetrandria class of
As I do in the country? pleasantly? that is, at leisure? plants; and in the natural method ranking under the
For which reason I do not care to write long letters, 48th order, Aggregate. The florets are tripetalous,
but to read them; the one as the effect of niceness, with one petal of each trifid; the receptacle is a little
and the other of idleness. For nothing is more idle villous ; there is no proper calyx ; the antheræ are al-
than your nice folks, or curious than your idle ones. most coalited.
Farewell.” Every sentence here consists of an anti- LEUCADIA, formerly called Neritis, a penin-
thefis, and a jingle of words, very different from the fula of Acarnania, (Homer); but afterwards, by
ftyle of conversation, and plainly the effect of study. cutting through the peninsula, made an island, as it
But this was owing to the age in which he lived, at is at this day, called Si Maura.
which time the Roman eloquence was sunk into puns, LEUCAS, (anc. geog.), formerly called Neritos
and an affectation of wit ; for he was otherwise a man and Neritum, a town of Leucadia or Leucas; situated
of fine sense and great learning.

near a narrow neck of land, or isthmus, on a hill fac
Letter of Aitorney, in law, is a writing by which cing the east and Acarnania : the foot or lower part
one perfon authorises another to do some lawful act of the town was a plain lying on the sea by which
in his stead; as to give feisin of lands, to receive debts, Leucadia was divided from Acarnania, (Livy); though
fue a third person, &c.

Thucydides places Leucas more inward in the island,
The nature of this inftrument is to transfer to the which was joined to the continent by a bridge. It
person to whom it is given, the whole power of the was an illustrious city, the capital of Acarnania, and
maker, to enable him to accomplish the act intended the place of general assembly.
to be performed. It is either general or fpecial : and LEUCATA, or Leucate, (anc. geog.); a pro-
fometimes it is made revocable, which is when a bare montory of Leucadia according to Strabo, a white
authority is only given; and sometimes it is irrevo- rock projecting into the sea towards Cephalenia, on
cable, as where debts, &c. are assigned from one per- which stood a temple of Apollo surnamed Leucadius.
fon to another. It is generally held, that the power At his festival, which was annually celebrated here, the
granted to the attorney must be strictly pursued; and people were accustomed to offer an expiatory facrifice
that where it is made to three persons, two cannot to the god, and to avert on the head of the victim all
execute it. In most cases, the power given by a let- the calamities with which they might be threatened.
ter of attorney determines upon the death of the per. For this purpose, they made choice of a criminal con-
fon who gave it. No letter of attorney made by any demned to die ; and leading him to the brink of the
Ramen, &c. in any fhip of war, or having letters of promontory, precipitated him into the sea amidst the
marque, or by their executors, &c. in order to em- loud shouts of the spectators. The criminal, how-
power any person to receive any share of prizes or ever, seldom perished in the water: for it was the
Bounty-money, shall be valid, unless the same be made custom to cover him with feathers, and to fasten birds

revocable, and for the use of such seamen, and be to his body, which by spreading their wings might
ligned and executed before, and attested by, the cap- serve to break his fall. No fooner did he touch the
tain and one other of the figning officers of the ship, fea, than a number of boats ftationed for the purpose
on the mayor or chief magistrate of some corporation. flew to his affiftance, and drew him out; and after be-

LETTAR of Mart or Marque. See MARQUE. ing thus saved, he was banished for ever from the

LETTERS Patent or Overt, are writings sealed with territory of Leucadia. (Strabo, lib. 10. p. 452.).
the great seal of England, whereby a man is autho- According to ancient authors, a ftrange opinion
rised to do, or enjoy any thing, which, of himself, concerning this promontory prevailed for some time
he could not do. See Patent. They are so called, among the Greeks. They imagined that the leap of
by reafon of their form; as being open, with the seal Leucata was a potent remedy against the violence of
affixed, ready to be shown for the confirmation of the love. Hence disappointed or despairing lovers, it is
authority given by them.

said, were often known to have come to Leucadia;.
LETTUCE, ia botany. Sec LACTUCA. and, having ascended the promontory, offered facri-

a

a

cap 87.

Leucippus fices in the temple, and engaged by a formal vow to LEUCOMA, in furgery, a distemper of the eye, Leucopetra. perform the desperate act, to have voluntarily preci- otherwise called albugo. See ALBUGO, and SURGERY.

B Leucoma.

Leuctra. pitated themselves into sea. Some are reported to have LEUCOPETRA, (anc. geog.) so called from its

recovered from the effects of the fall; and among o- white colour (Strabo); a promontory of the Bruttii, S Ptolem. thers mention is made 5 of a citizen of Buthroton, in in the territory of Rhegium : the termination of the Hepbe. Epirus, whose passions always taking fire at new ob- Apennine. The outmost extremity of the Bruttii, op. Phot,

jects, he four times had recourse to the same remedy, and or the modern Calabria Ultra ; as the Japygium is of P. 491.

always with the same success. As those who made the ancient Calabria, or the modern Calabria Citra.
the trial, however, feldom took any precaution to LEUCOPETRIANS, in ecclefiaftical history, the
render their fall less rapid, they were generally destroy- name of a fanatical sect which sprang up in the Greek
ed; and women often fell victims to this act of despe- and Eastern churches towards the close of the 12th
ration.--At Leucata was shown the tomb of Artemi- century : the fanatics of this denomination professed to

fia, that celebrated queen of Caria who gave so many believe in a double Trinity, rejected wedlock, abstain, + Herodot. proofs of courage at the battle of Salamis 7. Inflamed ed from flesh, treated with the utmost contempt the lib. S.

with a violent passion for a young man who inflexibly facraments of Baptism and the Lord's Supper, and all
refused her love, she surprised him in his sleep and put the various branches of external worship; placed the
dut his eyes. Regret and despair soon brought her to essence of religion in internal prayer alone, and main-

Leucata, where the perished in the waves notwithstand- tained, as it is faid, that an evil being, or genius,
Ptolem. ing every effort to save her. Such likewise was the dwelt in the brealt of every mortal, and could be ex.
Hepbaf. end of the unhappy Sappho. Forsaken by her lover pelled from thence ty no other method than by per-
ibid.,

Phaon, the came hither to seek relief from her suf- petual supplication to the Supreme Being. The
ferings, and found her death. (Menand. ap. Strab. founder of this enthusiastical sect is said to have been
lib. 10. p. 452.)

a person called Leucopetrus, and his chief disciple Ty-
LEUCIPPUS, a celebrated Greek philofopher chicus, who corrupted, by fanatical interpretations,
and mathematician; first author of the famous system several books of scripture, and particularly St Mat-
of atoms and vacuums, and of the hypothetis of storms; thew's gotpel.
fince attributed to the moderns. He flourished about LEUCOPHLEGMATIA, in medicine, a kind
428 B.C.

of dropsy, otherwise called anajarca. See (Index sub-
LEUCOGÆUS, (anc. geog.), a hill situated be- joined to) MEDICINE.
tween Puteoli and Neapolis in Campania, abounding LEUCOTHOE, or LEUCOTHEA (fab. hift.), the
in fulphur ;' now l'Alumera. Whence there were also wife of Athamus, changed into a sea deity ; fee Ino.
{prings called Leucogei fontes; the waters of which, ac- She was called Matuta by the Romans. She had a
cording to Pliny, gave a firmness to the teeth, clear- temple at Rome, where all the people, particularly
ness to the eyes, and proved a cure in wounds. women, offered vows for their brother's children.

LEUCOJUM, GREAT SNOW-DROP: a genus of They did not intreat the deity to protect their own
the monogynia order, belonging to the hexandria class children, because Ino had been unfortunate in hers.
of plants; and in the natural method ranking under No female llaves were permitted to enter the temple ;
the ninth order, Spathacea. The corolla is campanu- if their curiolity tempted them to tranfgress this
lated, sexpartite, the segments increased at the points, rule, they were beaten with the greatest severity. To
the stigma fimple.

this fupplicating for other people's children, Óvid al-
Species. 1. The vernum, or spring leucojum, ludes in these lines ;
has an oblong bulbous root, sending up several

Non tamen bane pro ftirpe fua pia mater adorat,
Hat leaves fix or eight inches long; and amidst them

Ipfa parum felix vila fuiffe parens. Faft. 6.
an upright, channelled, hollow, naked ftalk, about LEUCTRA, (anc. geog.), a town of Bæotia, to
a foot high, terminated by a spatha, protruding one or the west of Thebes, or lying between Platex and Thef-
two white flowers on Nender footitalks drooping down- piæ, where the Lacedemonians had a great defeat gi-
wards, and appearing in March. 2. The æftivum, or ven them by Epaminondas and Pelopidas the Theban
fummer leucojum, has a large, oblong, bulbous root, generals. The Theban army confifted at most but of
crowned with several long, Nat, broad leaves ; and a 6000 men, whereas that of the enemy was at least
midst them an upright, thick, hollow stalk, 15 or 18 thrice that number : but Epaminondas trusted most in
inches high ; terminated by a spatha, protruding many his horse, wherein he had much the advantage, both
white flowers, on Nender foot talks, drooping down in their quality and good management; the reft he en-
wards; flowering in May. 3. The autumnale, or au- deavoured to supply by the disposition of his men, and
tumnal leucojum, hath a large oblong bulbous root, the vigour of the attack. He even refused to suffer
crowned with many narrow leaves, an upright, naked, any to serve under him in the engagement, but such
hollow stalk, terminated by a spatha protruding many as he knew to be fully resolved to conquer or die. He
white flowers on long weak footftalks, hanging down- put himself at the head of the left wing, oppofite to
wards, and flowering in autumn.

Cleombrotus king of Sparta, and placed the main
Culture. All the three species are very hardy, du- ftress of the battle there ; rightly concluding, that if
rable in root, and increase exceedingly by offsets, which he could break the body of the Spartans, which was
may be feparated every two or three years.

but 12 men deep, whereas his own was 50, the rest LEUCOMA, in antiquity, was a public register would be soon put to flight. He closed his own with: amongft the Athenians, in which were inserted the the sacred band, which was commanded by Pelopidas; names of all the citizens, as soon as they were of age and placed his horse in the front. His right, front. to enter upon their paternal inheritance.

a

Leudra, back, in a fanting line, as if they declined to fight, This application of a bubble of air was the invention Level
Level.

that they might not be too much exposed to the e- of Dr Hooke.
nemy, and might serve him for a corps of reserve in There is one of these instruments made with sights, being
cafe of need. This was the wise disposition which the an improvement upon that last described, which, by the
two Theban generals made of their few but resolute addition of more apparatus, becomes more commodious
forces; and which succeeded in every part, according and exact. It confiits of an air-level, fig. 1. about eight

Plate

CCLXX
to their wish. Epaminondas advanced with his left inches long, and seven or eight lines in diameter, set
wing, extending it obliquely, in order to draw the ene- in a brass tube, 2, with an aperture in the middle,
my's right from the main body; and Pelopidas char- C. The tubes are carried in a strong straight ruler, a
ged them with such desperate speed and fury, at the foot long; at whose ends are fixed two fights, 3, 32
head of his battalion, before they could reunite, that exactly perpendicular to the tubes, and of an equal
their horse, not being able to stand the shock, were height, having a square hole, formed by two fillets of
forced back upon their infantry, which threw the brass crossing each other at right angles, in the middle
whole into the greatest confusion : so that though the whereof is drilled a very little hole, through which a
Spartans were of all the Greeks the most expert in re- point on a level with the instrument is descried. The
covering from any surprise, yet their skill on this oc- brass tube is fastened on the ruler by means of two
calion either failed them or proved of no effect ; for screws ; one whereof, marked 4, serves to raise or de-
the Thebans, observing the dreadful impression they press the tube at pleasure, for bringing it towards a
had made on them with their horse, pushed furiously level. The top of the ball and socket is rivetted to a
upon the Spartan king, and opened their way to him little ruler that springs, one end whereof is fastened
with a great Naughter.

with screws to the great ruler, and at the other end has
Upon the death of Cleombrotus, and several officers a screw, 5, ferving to raise and depress the instrument
of note, the Spartans, according to custom, renewed when nearly level.
the fight with double vigour and fury, not so much to The instrument juft described, however, is yet less
revenge his death as to recover his body, which was commodious than the following one ; because though
such an established point of honour as they could not the holes be ever so small, yet they will still take in too
give up without the greatest disgrace. But here great a space to determine the point of level precisely.
the Theban general wisely chose rather to gratify The instrument alluded to consists of an air-level, with
them in that point, then to hazard the suceess of a telescope fights. This level (fig. 2.) is like the last; with
fecond onset; and left them in possession of their this differepce, that, instead of plain fights, it carries a
king, whilft he marched straight against their other telescope to determine exactly a point of level at a
wing, commanded by Archidamus, and confifted chiefly good distance. The telefcope is a little brass-tube,
of such auxiliaries and allies as had not heartily enga- about 15 inches long, fastened on the same ruler as the
ked in the Spartan interest: these were so discou- level. At the end of the tube of the telescope, mark-
raged by the death of the king and the defeat of ed 1, enters the little tube 1, carrying the eye-glafs
that wing, that they betook themselves to fight, and and an hair horizontally placed in the focus of the ob-
were presently after followed by the rest of the army. ject-glass, 2; which little tube may be drawn out, or
The Thebans, however, pursued them so closely, that pushed into the great one, for adjusting the telescope
they made a second dreadful flaughter among them; to different lights : at the other end of the telescope is
which completed Epaminondas's victory, who remain- placed the object-glass. The screw 3, is for railing
ed master of the field, and erected a trophy in memory or lowering the little fork, for carrying the hair, and
of it. This was the conclusion of the famed battle of making it agree with the bubble of air when the in-
Leuctra, in which the Lacedemonians loft 4000 men, strument is level; and the screw 4, is for making the
and the Thebans but. 300.

bubble of air, D or E, agree with the telescope: the
LEVEL, an instrument wherewith to draw a line pa- whole is fitted to a ball and socket. M. Huygens is
rallel to the horizon, by means of which the true level, or said to be the first inventor of this level ; which has this
the difference of ascent or descent between several places, advantage, that it may be inverted by turning the ru-
may be found, for conveying water, draining fens, &c. ler and telescope half round; and if then the hair cut

There are several instruments of different contrivance the fame point that it did before, the operation is just.
and matter, invented for the perfection of levelling; al It may be observed, that one may add a telescope to
of which, for the practice, may be reduced to the any kind of level, by applying it upon, or parallel to,
following.

the base or ruler, when there is occafion to take the le-
Air-Lever, that which fhows the line of level by vel of remote objects.
means of a bubble of air inclosed with some liquor in Dr Desaguliers contrived an instrument, by which
a glass-tube of an indeterminate length and thickness, the difference of level of two places, which could not
whose two ends are hermetically sealed. When the be taken in less than four or five days with the best
bubble fixes itself at a certain mark, made exactly in telescope-levels

, may be taken in as few hours. The
the middle of the tube, the plane ar ruler wherein it instrument is as follows. To the ball C (fig. 3.) is
is fixed is level. When it is not level, the bubble will joined a recurve tube B A, with a very fine bore, and
rise to one end. This glass-tube may be set in another a small bubble at top A, whose upper part is

open. of brass, having an aperture in the middle, whence the It is evident from the make of this instrument, that bubble of air may be observed. The liquor wherewith if it be inclined in carrying, no prejudice will be done the tube iü filled is oil of tartar, or aqua fecunda ; to the liquor, which will always be right both in the these not being liable to freeze as common water, nor ball and tube when the instrument is set upright. If to rarefaction and condensation, as fpirit of wine is. the air at C be so expanded with heat, as to drive the

6

liquor

a

а

a

Level. liquor to the top of the tube, the cavity A will receive in gardens, plantations, and the conveyance of water, Level.

the liquor, which will come down again and settle at where an experiment that answers two or three feet in
D, or near it, according to the level of the place a distance of 20 miles, will render this a very useful
where the instrument is, as soon as the air at C returns instrument.
to the same temperament as to heat and cold. To Artillery Foot-Level is in form of a square, having
preserve the same degree of heat, when the different its two legs or branches of an equal length ; at a junc-
observations are made, the machine is fixed in a tin vef- ture whereof is a little hole, whence hangs a thread
fel EF, filled with water up to g h, above the ball, and plummet playing on a perpendicular line in the
and a very sensible thermometer has also its ball under middle of a quadrant. It is divided into twice 45°
water, that one may observe the liquor at D, in each degrees from the middle. Fig. 7.
experiment, when the thermometer stands at the same This inftrument may be used on other occasions, by
height as before. The water is poured out when placing the ends of its two branches on a plane ; for
the instrument is carried; which one may do conve- when the thread plays perpendicularly over the middle
niently by means of the wooden frame, which is set division of the quadrant, that plane is assuredly level.
upright by the three screws, S, S, S, fig. 4. and To use it in gunnery, place the two ends on the piece
a line and plummet P P, fig. 5. At the back part of of artillery, which you may raise to any proposed
the wooden frame, from the piece at top K, hangs the height, by means of the plummet, whofe thread will:
plummet P, over a brafs point at N; Mm are brackets give the degree above the level

.
to make the upright board K N continue at right Carpenter's and Puvior's Level, consists of a long
angles with the horizontal one at N. Fig. 6. represents ruler, in the middle whereof is fitted, at right angles,
a front view of the machine, supposing the fore part another fomewhat bigger, at the top of which is
of the tin-veffel transparent; and here the brass-focket fastened a line, which, when it hangs over a fiducial
of the recurve-tube, into which the ball is screwed, has line at right angles with the base, shows that the said:
two wings at II, fixed to the bottom, that the ball base is horizontal. Sometimes this level is all of one.
may not break the tube by its endeavour to emerge board. Fig. 8.
when the water is poured in as high as g h.

Gunner's Level, for levelling cannons and mortars, After the Doctor had contrived this machine, he consists of a triangular brass plate, about four inches. considered, that as the tube is of a very small bore, if high, fig. 9. at the bottom of which is a portion the liquor should rise into the ball at A (fig. 3.) in car- of a circle, divided into 45 degrees ; which number rying the instrument from one place to another, some is sufficient for the highest elevation of cannons and of it would adhere to the sides or the ball A, and up- mortars, and for giving shot the greatest range : on. on its descent in making the experiment, so much the centre of this segment of a circle is screwed a piece might be left behind, that the liquor would not be of brass, by means of which it may be fixed or screwed high enough at D to show the difference of the level : at pleafure: the end of this piece of brass is made for therefore, to prevent that inconveniency, he contrived as to serve for a plummet and index, in order to show a blank screw, to shut up the hole at A, as soon as one the different degrees of elevation of pieces of artillery. experiment is made, that, in carrying the machine, the This instrument has also a brass foot, to set upon canair in A may balance that in C, so that the liquor nons or mortars, so as, when those pieces are horizonShall not run up and down the tube, whatever degree tal, the instrument will be perpendicular. The foot of heat and cold may act upon the instrument, in go- of this inftrument is to be placed on the piece to be ing from one place to another. Now, because one ex• elevated, in such a manner, as that the point of the periment may be made in the morning, the water may plummet may fall on the proper degree: this is what be so cold, that when a second experiment is made at they call levelling the piece. noon the water cannot be brought to the fame degree Mason's Level, is composed of three rules, so join-.. of cold it had in the morning ; therefore, in making ed as to form an isosceles-rectangle, somewhat like a the first experiment, warm water must be mixed with Roman A; at the vertex whereof is fastened a thread, the cold, and when the water has stood some time, be- from which hangs a plummet, that passes over a fidufore comes to be as cold as it is likely to be at the cial line, marked in the middle of the base, when the warmest part of that day, observe and set down the de- thing to which the level is applied is horizontal; but gree of the thermometer at which the spirit stands, declines from the mark, when the thing is lower on and likewise the degree of the water in the barometer the one side than on the other. at D; then screw on the cape at A, pour out the wa- Plumb or Pendulum Lerel, that which shows the ter, and carry the instrument to the place whose level horizontal lines by means of another line perpendicular you would know; then pour in your water, and when to that described by a plummet or pendulum. This the thermometer is come to the same degree as before, inftrument, fig. 10. confifts of two legs or branches, open the screw at top, and observe the liquor in the joined together at right angles, whereof that which barometer.

carries the thread and plummet is about a foot and a The Doctor's scale for the barometer is ten inches half long ; the thread is hung towards the top of the long, and divided into tenths; so that such an inftru- branch, at the point 2. The middle of the branch ment will serve for any heights not exceeding ten feet, where the thread paffes is hollow, so that it may hang each tenth of an inch answering to a foot in height. free every where : but towards the bottom, where there

The Doctor made no allowance for the decrease of is a little blade of filver, whereon is drawn a line per density in the air, because he did not propose this ma- pendicular to the telefcope, the faid cavity is covered ehine for measuring mountains (though, with a proper by two pieces of brass, making as it were a kind of allowance for the decreasing density of the air, it will case, left the wind should agitate the thread; for which do very well), but for heights that want to be known reason the filver blade is covered with a glass. G, to the

end

а

а

a

a

Level. end that it may be seen when the thread and plummet without turning the level. In the focus of the object- Level.

play upon the perpendicular: the telescope is fastened glass of each telescope must a little hair be strained ho-
to the other branch of the instrument, and is about rizontally, to be raised and lowered as occasion requires
two feet long; having an hair placed horizontally a- by a little screw. If the tube of the telescope be not
cross the focus of the object-glass, which determines found level when suspended, a ferril or ring, 4, is put
the point of the level. The telescope must be fitted on it, and is to be did along till it fixes to a level..
at right angles to the perpendicular. It has a ball The hook on which the instrument is hung is fixed to
and socket, by which it is fastened to the foot, and a flat wooden cross; at the ends of each arm whef
was invented by M. Picard.

there is a hook serving to keep the telescope from
Refleding Level, that made by means of a pretty too much agitation in using or carriage. To the said
long surface of water representing the same object in- Aat cross is applied another hollow one, that serves as
verted which we see erected by the eye, so that the. a case for the instrument; but the two ends are left
point where these two objects appear to meet is a level open, that the telescope may be secured from the wea-
with the place where the surface of the water is found. ther and always in a condition to be used. The foot
This is the invention of M. Marriotte.

of this instrument is a round brass plate, to which are There is another reflecting level consisting of a mir- faftened three brass ferrils, moveable by means of joints ror of steel, or the like, well polished, and placed a whereon are put ftaves, and on this foot is placed little before the object-glass of a telescope, suspended the box. perpendicularly. This mirror must make an angle of Fig. 12. marked I, is a balance-level ; which being, 45° with the telescope, in which case the perpendicu- suspended by the ring, the two fights, when in aquis lar line of the said telescope is converted into a horizon-. librio, will be horizontal, or in a level. tal line, which is the same with the line of level. This Spirit LEVEL. The most accurate levelling inftru-, is the invention of M. Cassini.

ment, and that possessed of the greatest essential advanWater-LEVEL, that which shows the horizontal line tages in use, is the spirit-level; which was first conby means of a surface of water or other liquor; found. structed by the late Mr Siffon, and to which fome, ed on this principle, that water always places itself small additions and improvements have been fince made. level.

The following is a description of one of the best of The moft fimple is made of a long wooden trough these levels, as made by the principal mathematical or canal, whose fides are parallel to the base ; so that instrument makers. being equally filled with water, its surface shows the Fig. 13. is a representation of the instrument mountline of level. This is the chorobates of the ancients.ed on its complete staves, copied (except the letters) See CHOROBATA.

from Mr Adams's Graphical Efsays, Plate xvii. fig. 3. It is also made with two cups fitted to the two ends. The telescope (ABC) is made from 15 inches to 2 of a pipe, three or four feet long, about an inch in feet in length, as may be required. It is achromatic, diameter, by means whereof the water communicates of the best kind, and shows the objects erect. In the from the one to the other cup; and this pipe being focus of the eye-glasses are exceedingly fine cross wires, moveable on its stand by means of a ball and socket, the intersection of which is evidently shown to be when the two cups become equally full of water, their perfectly in the axis of the tube ; for by turning it two surfaces mark the line of level.

round on its two supporters DE, and looking through
This inftrument, instead of cups, may also be made the telescope, the intersection of the wires will con-
with two short cylinders of glass three or four inches (tantly cut the fame part of the object viewed. By
long, fastened to each extreme of the pipe with wax turning the screwa at the side of the telescope, the object-
or maftic. Into the pipe is poured some common or glass at g is moved ; and thus the telescope is exactly a-
coloured water, which shows itself through the cylin- dapted to the eye. If these cross wires are at any time
ders, by means whereof the line of level is determined; out of their adjustment, which is discovered by their
the height of the water, with respect to the centre of intersection not cutting the same part of the object
the earth, being always the fame in both cylinders ; during the revolution of the telescope on its axis, they
this level, though very simple, is yet very commodious are easily adjusted by means of the four screws bbb,
for levelling small distances.

placed on the telescope about an inch from the end
Level of Mr Huygens's intention, consists of a tele. for the eye. These screws act in perpendicular di-
scope a, fig. 11. in form of a cylinder, going through rections to one another, by unscrewing one and tight-
a ferril, in which it is fastened by the middle. This ening the other opposite to the wire, so that if connected
ferril has two fat branches bb, one above, and the other with it, it may be moved either way at pleasure ; and
below: at the ends whereof are fastened little moving in this manner the other wire perpendicular to it may
pieces, which carry two rings, by one of which the be moved, and thus the interfection of the wires brought
telescope is suspended to an hook at the end of the exactly in the axis of the tube.
fcrew 3, and by the other a pretty heavy weight is To the telescope is fixed, by two small screws cr, the
suspended, in order to keep the telescope in equilibrio. level tube containing the spirits, with a small bubble
This weight hangs in the box 5, which is almost filled of air: This bubble of air, when the instrument is
with linseed oil, oil of walnuts, or other matter that well adjusted, will settle exactly in the same place, in
will not easily coagulate, for more aptly settling the or near the middle of its tube, whether the telescope
balance of the weight and telescope. The instrument be reversed or not on the supporters, which in this
carries two telescopes close and very parallel to each case are kept unmoved.
other; the eye-glass of the one being against the ob- It is evident, that the axis of the telescope, or the
ject glass of the other, that one may fee each way intersection of the wires, as before shown, mull be in this
No 181.

4

cafe