MAKING CERTAIN MACHINES OR INSTRUMENTS, WHICH WILL NOT ONLY SAVE MUCH TIME AND TROUBLE IN CALCULATING THE LONGITUDE, BUT BE LESS LIABLE TO ERE THAN ANY OF THE METHODS NOW IN USE
Year: 1790

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ESTIENNE
LEGUIN, of New Compton Street, in the Parish of Saint Giles-in-the-Fields,
in the County of Middlesex, Optician, send greeting.
WHEREAS His present Majesty, in and by His certain Letters Patent
under the Great Seal of Great Britain, bearing date at Westminster, the First
day of June, in the thirtieth year of His reign, did, for Himself, His heirs and
successors, give and grant unto me, the said Estienne Leguin, my executors,
administrators, and assigns, His especial license, full power, sole privilege and
authority, that I, the said Estienne Leguin, my executors, administrators, and
assigns, and every of them, by myself and themselves, or by my or their deputy
or deputies, servants or agents, or such others as I, the said Estienne Leguin,
my executors, administrators, or assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term of years
therein expressed, should and lawfully might make, use, exercise, and vend my
Invention of "MAKING CERTAIN MACHINES OR INSTRUMENTS, WHICH WILL NOT
ONLY SAVE MUCH TIME AND TROUBLE IN CALCULATING THE LONGITUDE, BUT BE
LESS LIABLE TO ERE THAN ANY OF THE METHODS NOW IN USE," as therein men-
tioned, within that part of the Kingdom of Great Britain called England, the
Dominion of Wales, and Town of Berwick-upon-Tweed, in such manner as to
me, the said Estienne Leguin, my executors, admors, and assigns, or any of
them, should seem meet, and that I, the said Estienne Leguin, my executors,
administrators, and assigns, should and lawfully might have and enjoy the

page_text: whole profit, benefit, commodity, and advantage. from time to time coming,
growing, accruing, and arising by reason of the said Invention, for and during
the term of years therein mentioned, to hold, exercise, and enjoy the said
license, powers, privileges, and advantages therein-beforo granted or mentioned
to be granted unto me, the said Estienne Leguin, any executors, adiiors, and
assigns, for and during and unto the full end and term of fourteen years from
the date of the said Letters Patent next and immediately ensuing, and fully to
be complete and ended, according to the Statute in such case made and pro-
vided; in which said Letters Patent is contained a proviso that the same
should be voil, unless T, the said Estienne Leguin, should particularly describe
and ascertain the nature of the said Invention, and in what manner the same
was to be performed, 'by an 'instrument in writing under my hand and seal,
and cause the same to be inrolled in the High Court of Chancery within
one calendar month next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, thia't I, the said 'Estionno Leguin, in pursuance of the
said proviso in the said Letters Patent, do hereby describe and ascertain tho
nature of the said Invention, and in what manner the same is to be performed.
as follows, that is to say:-
The said Invention consists of 'two machines or instruments, as may be seen
in the representation or delineation thereof drawn in the margin of these Pro-
sents, and marked respectively with the figures 1 and 2. That marked with
the figure 1 consists of a semicircular wood frame, cased on its outward rim
with a metal plate, and which I call a semicircle, describing upon its surface
one hundred and eighty principal divisions, 'beginning at 0, which are intended
'for degrees, and these degrees are subdivided 'into half degrees. The two ends
of the semicircle are connected by a 'bar; and 'from the center of this bar to
the center of the semicirelo another bar is fixed, to 'strengthen and preserve it
from injury. From the center of the last-mentioned bar, upon the end adjoining
the first-mentioned bar, an index is made to move on an axis of steel, described
in the Figure by the letter 1, over the semicircle containing such degrees, for the
purpose of defining the minutes and seconds. At or near 0, or the first division
on the semicircle, a piece of steel pierced with a small hole is inserted for tho
purpose of receiving and securing one of the points of the compass, herein-after
described and refered to by figure 2. This piece of steel is denoted in Figure
i with the letter'S. 'A similar piece of steel 'is also inserted at the top of the
nonius, in the under part of the left side, denoted in the Figure by the letter X,
to facilitate the operations herein-after described; and the intent is, that the
small hole in the first piece of steel referred to shall be at 'the same distance

page_text: from 0, or the first division on the semicircle, as the hole in the second piece
of steel is from the first division on the nonius. The semicircle and nonius may
respectively be made either of brass entirely, or of silver, or any other metal fit
for the purpose; or they may be made of ivory, wood, or any other substance
5 or thing fit for the purpose. The ponius may be also made to slide on the semi-
circle independent, and without being connected to the index at the center of
the bar described by the letter u.
The other part of the Invention already referred to by figure 2, consists of a
compass with four legs (marked in the Figure with the letters A, B, C, D), which
。 I make partly of brass and partly of steel, as compasses usually are; but which,
nevertheless, may be made of silver or any other metal or thing fit for the purpose;
all of which legs move upon an axis, described in the Figure by the letters N, M.
The two legs C, D, as may be collected from the Figure, are made to move
horizontally, and the legs A, B, are made to move vertically. If the leg marked
5 C is united to the leg marked B, and the leg marked D to that of A, and then
the legs B, C, and D, A, so united, are moved vertically or downwards, the
four points will connect together, and as it were form but one. The size or
extent of the compass must be governed by the size or extent of the semicircle,
so that when the former is opened in the manner described in the Drawing
O annexed, marked with the figuro 8, each point should measure, as nearly as
may be, from the, other, ninety degrees upon the semicircle.
PREPARATIVE FOR THE OPERATION.
Having taken, with a sextant, quadrant, or other instrument fit for the pur-
pose, the distance between the sun and the moon, the apparent height of the sun,
5 and the apparent height of the moon, and found the correction of the sun and
the correction of the moon, deduct ten times the correction of the sun from its
apparent height, and add ten times the correction of the moon to its apparent
height; then add ten times the correction of the sun to its apparent height,
and deduct ten times the correction of the moon from its apparent height.
OPERATION.
Having fixed the nonius upon the semicircle at the apparent height of the
sun, measure the distance with the legs B, C, between the holes X and S, and
then shift the nonius to the apparent height of the moon, and measure the
she love of the compass A D next plane the

page_text: occasion may require; then place the legs C, B, in like manner upon the sun's
apparent height, after deducting ten times its correction, and the legs D, A, upon
the apparent height of the moon, after having added ten times its correction;
then look on the semicircle for the degrees and minutes, between the legs
D and C (taking care that the legs A, B, do not separate during the operation),
and write them down.
Secondly, place the legs C, B, upon the sun's apparent height, after having
added ten times its correction, and the legs D, A, upon the apparent height of
the moon, after having deducted ten times its correction; then look upon the
semicircle for the degrees and minutes between the legs C and D, and write
them down. Subtract the two numbers so found from one to another, and
multiply the remainder by 8, and take the degrees for minutes, and the minutes
for seconds. Subtract this remainder from the apparent distance of the sun
and moon, if the first number is smaller than the second; but if the contrary, it
is to be added, and it will give you the true distance of the sun and moon.
Note, in case it happens that the moon's correction, ten times multiplied, .is
greater than its apparent height, the leg D must be put the contrary way to
A, in order to reduce them so much in the operation. This operation may be
performed in like manner by taking the altitude of a star, instead of the altitude

page_text: then place, in like manner, the nonius on the latitude of the observation, and
take the distance with the legs A, D; next place the nonius on the complement
or corrected height with the legs D, C, and (observing the directions given in
the preceding operation, and the distance then of the legs A, B, measured on
the semicircle, will be the horary angle.
Note, when the latitude and declination are both north or both south, the
legs of the compass C, D, must be on the same side; but when the latitude is
north and the declination south, or vice versa, the legs C, D, must be opposed
to each other in the above operation. As this instrument resolves all kinds of
spherical triangles, you may dispense with taking the height of the sun and
moon, of which you have taken the distance, by bringing the longitude estimated
to the longitude of Greenwich.
Find in the Nautical Almanack the hororay angle, place the leg A, D, on the
latitude of the place of observation, and the leg C, B, on the declination, the
legs A, B, on the horary angle, the legs D, C, will be the complement of the
true height; then bring the correction necessary to have the apparent height.
In witness whereof, I, the said Estienne Leguin, have hereunto set my hand
and seal, this Thirtieth day of June, in the year of our Lord One
thousand seven hundred and ninety.
ESTIENNE LEGUIN (L.B.)
AND BE IT REMEMBERED, that on the Thirtieth day of June, in the
year of our Lord 1790, the aforesaid Estienne Leguin came before our said
Lord the King in His Chancery, and acknowledged the Specification aforesaid,
and all and every thing therein contained and specified, in form above written.
And also the Specification aforesaid was stampt according to the tenor of the