PEN 
all, and ypccQu), to trace or delineate.] An inftrument de- 
defigned for drawing figures in what proportion you 
pleafe, without any fkill in the art. The inftrument is 
otherwife called a parallelogram. The following is the 
defcription of it by Mr. Adams. “ It is an inftrument 
as ufeful to the experienced draftfman as to thofe who 
have made but little progrefs in the art. It faves a great 
deal of time, either in reducing, enlarging, or copying of 
the fame fize, giving the outlines of any drawing, how¬ 
ever crooked or complex, with the utmoft exaftnefs ; nor 
is it confined to any particular kind, but may with equal 
facility be ufed for copying figures, plans, fea-charts, 
maps, profiles, landfcapes, &c. I have not been able to 
afcertain who was the inventor of this ufeful inftrument. 
The earlieft account I find is that of the Jefuit Scheiner, 
about the year 1631, in a fmall trad! entitled Pantogra- 
phice, Jive ars nova delineandi. The principles are lelf- 
evident to every geometrician 5 the mechanical conftruc- 
tion was firft improved and brought to its prefent (late 
of perfedlion by my father, about the year 1750. It is 
one, among many other fcientific improvements and in¬ 
ventions completed by him, that others have inglorioully, 
and many years after, affumed to themfelves.” 
The pantograph is ufually made of wood or brafs, and 
confifts of four flat rules, two of them long, and two 
fhort. See the annexed Plate, fig. 1. The two longed 
are joined at the end A, by a double pivot, which is fixed 
to one of the rules, and works in two fmall holes placed 
at the end of the other. Under the joint is an ivory caf- 
tor, to fupport this end of the inftrument. The two 
fmaller rules are fixed by pivots at E and H, near the 
middle of the larger rules, and are alfo joined together at 
their other end, G. By the conftruftion of this inftru¬ 
ment, the four rules always form a parallelogram. There 
is a Aiding box on the longer arm, and another on the 
ftiorter arm. Thefe boxes may be fixed at any part of the 
rules by means of their milled nuts ; each of thefe boxes 
is furnifhed with a cylindrical tube, to carry either the 
tracing-point or crayon or fulcrum. The fulcrum or 
fupport K, is a leaden weight inclofed in a mahogany 
box; on this the inftrument moves when in ufe. There 
are two moveable rollers, to fupport and facilitate the 
motions of the pantograph, their fituation may be varied 
as aecafion requires. The graduations are placed on two 
of the rules j on each of them are two fcales ; the fiducial 
edges of the boxes are to be fet to thefe, according to the 
work to be performed by the inftrument. The crayon, 
the tracer, and fulcrum, muft in all cafes be in a right 
line 5 fo that, when they are fet, if a ft ring be ftretched 
over them, and they do not coincide with it, there is an 
error either in the fetting or graduations. The long tube, 
which carries the pencil or crayon, moves eafily up or 
down another tube ; there is a firing affixed to the long 
or inner tube, palling afterwards through the holes in the 
three fmall knobs to the tracing-point, where it may, if 
neceffary, be fattened. By pulling this firing, the pencil 
is lifted up occafionally, and thus prevented from making 
falfe or improper marks upon the copy. 
To ufe this injlrument when the copy is to he of the fame 
fize as the original. —Place the inftrument upon a large 
table, and fet the Hiding-boxes B and D to the divifions 
there marked 1, 2. Put the crayon into the box B, place 
the box D upon the fulcrum, or leaden foot; the tracing- 
point at C. Then lay a piece of paper under the crayon, 
and the original drawing under the tracer, and move the 
tracing-point over the principal ftrokes of the original, 
and the crayon will form the required copy. 
To reduce a drawing, fyc. to half the fize of the original. 
— Set the boxes B and D to the divifions marked place 
the fulcrum at B, the crayon at D, and the tracer at C. 
To reduce a drawing to lefs than one half. —Suppofe one- 
third, one-fourth, one-fifth, , See. Place the fulcrum at 
B, crayon at D, and tracer at C, and Aide the boxes B and 
D to the divifions marked ■§■, -i, & c. on the longer fcales. 
It may be proper to obferve here, that if the copy be lefs 
Vol. XIX. No. 1325. 
PEN 567 
than one-half the original, or when it is required greater 
than the original, the longer fcales are to be ufed. 
For greater than one-half the original drawing. —Suppofe 
it be required to make a drawing, two-thirds, three, 
fourths, four-fifths, See. Set the Boxes B and D to cor¬ 
refponding divifions, as §, f, ■£, &c. on theJhorterfcales, 
place the fulcrum at D, the crayon at B, and tracer at C. 
When the original drawing is to be enlarged. —Suppofe 
one-eighth, one-fixth, &c. fet the Boxes B and D, to 
&c. on the longer fcales, place the fulcrum at D, the crayon 
at C, and tracer at B. 
Where the copy is required of a fize differing from the 
fraStional parts laid down on the injlrument. —For this pur- 
pofe there are two fcales laid down, containing 100 un¬ 
equal parts; one fcale numbered from to to Bo, the other 
from 50 to too. 
If the copy is to he under one-half the original fize , place 
the boxes B and D to any two correfponding divifions 
under 50 ; the fulcrum at B, and crayon at D. 
If the copy is to be larger than one-half the original, place 
the boxes B and D to correfponding divifions between 
50 and 100 , the fulcrum at B, and crayon at D. 
To change the fituation of the pantograph. —'Copy firft as 
much as the pantograph will take in 5 then make three 
points on the original, and as many correfponding points 
on the copy. Then remove the fulcrum to another fitu¬ 
ation, but fo that, when the tracing-point is applied to the 
three points marked on the original, the crayon may ex¬ 
actly coincide with the other three points on the copy, 
and proceed as before ; and fo on for every change in the 
fituation of your inftrument, and by this means a panto¬ 
graph of two feet and a half in length will copy a draw¬ 
ing of any fize whatfoever. 
The eonftruftion of this inftrument (fays Mr. Cham¬ 
bers) requires a confiderable degree of accuracy; for 
which reafon there are very few of the inftruments that 
fucceed. Few will do any thing tolerably but ftraight 
lines; and many of them not even thofe. In order to 
prove that the figure deferibed by a pentagraph is fimilar 
to the given figure ; let C, fig. 2, be the fixed centre of 
motion ; P the pencil for tracing the given figure P P, 
and p the pencil which traqes the other figure pp; p, &c. 
muft be fo adjufted,thatp, C, and P, may lie in one ftraight 
line; then, fince Bp : Aj) :: BP : A C, whatever be the 
fituation of the pentagraph, the angles P C P and p C p, 
are vertical; and, therefore, PCp will in every poiition 
of the inftrument be a right line ; but PCipCuBA: 
A p, in each of the two pofitions in the figure, and con- 
fequently the triangles P C P, p C p, are fimilar ; and P P 
: pp (:: PC : Cp) : : BA: Ap, or in a given ratio. 
Hence it appears, that by moving the pencil p, A p may be 
equal to B A, or lefs in any proportion; and confequently 
pp may be equal to P P, or lefs in the lame proportion. 
We have heard of a very recent improvement upon the 
pentagraph, for which indeed a patent is now (March 
1823) making out, which will be extremely ufeful, not 
to draughtfmen only, but to engravers. The ingenious 
artift, Mr. A. Smith, of Wingrove-place, St. John-ftreet 
Road, calls his invention the apograph. We (hall have 
an opportunity, probably, of defcribing it under fome 
future article. 
PENTAGYN'IA,/. [from the Gr. trine, five, and yvvc, 
a female.] The name of an order which occurs in the 
5th, 10th, nth, 12th, and 13th, clafles of the Linnasan ar¬ 
tificial fyftem. Its charafter depends, as the name ex- 
prefles, on the prefence of five ftyles, or, if ftyles be want¬ 
ing, of fo many felfile ftigmas. In the 12th clafs how¬ 
ever, Icofandria, it is neceflary to take this charadter with 
confiderable latitude. Plants of the natural tribe of po- 
macees, which make an important part of that clafs, are 
very uncertain as to the number of their ftyles in the fame 
genus, and even variable in the fame fpecies. Hence Dr. 
Smith has, in his Introdudlion to Botany, prefumed to 
advife that the order in quettion fliould admit flowers 
with from two to five ftyles, or even a few more occafion- 
7 F ally. 
