DENDROMETER, 
x 2: - {crews with nutes, a hoy in middle of ‘the long 
{lits of the two arms, to wedge them open, whereby the 
vibration is deftroyed, and ie arms, don hihi 
dered ftiff: 4, 4. 4, 4, are ferews and nuts 
from fplitting. With pia to the general conftruétion, 
ufe, and improvements that may be oa to it, Mr. Bread 
expreffes himfelf in the following ma 
“The inftrument is Pe e a pee Rraight pieces of 
well-feafoned deal, a 13 feet long, joine 
rough 
length nor thicknefs is of any particular con- 
scle as by following the directions ‘hereafter given, 
they be made of any fize. A little way from the 
pee pe isa brafs limb, I call the index, on which are 
g the quarter-girth in feet and 
wide 
wichowt Se ‘ng it, alae the graduated fide of the index 
mokt, which the greater girth will be fhewn, after 
gee ae a" bark, by the inner edge of the brafs on the 
right-hand leg. An operation fo ealy and fimple, that a 
perfor of the meaneft capacity might meafure a great num- 
height of atree, I would recommend 
o as to fit into ferrils at 
other, tapering ail the way in the fam 
manner as a fifhing-rod. {ct of five of them with feet 
marked on them, would enable a man quickly to meafure a 
of more than 40 feet high, as he would be able to 
— himfelf about ae eet, 
he improvements it is cdpable me are, making a joint 
in a arch or fcale, to enable it to fhut up, (when the legs 
- aia towards the centre, whic a ould make it eafier 
arry. Secondly, as it fometimes happens that ftanding 
es is fold without any allowance for bark, and at other 
times with a lefs allowance than one inch in 13, two other 
{eales on the index might be added in fuch cafes, one with- 
out any allowance, and the other to allow-as might be 
would have added thefe, but thought the fo- 
a) 
r bark, and is calculated on the following data. 
The diameter of a circle, whofe lb eg ll eas is 26 
inches, is 33.96 inches. ‘I'he diam ter of a circle, whofe 
quarter-girth is 65 inches, is 8.27 are. 
teale, the inflrument is opened fo as to take in at 
3 
~ 
8 o 
‘ 
for ‘fetting that 
nometrical paces will upon examination be found to be 
nothing more than trigonometrical methods abridged or dif- 
eur. The general principle upon which ail tne aah aes 
of plane trigonometry depend, is to find out three of the 
fix parts of a triangle, when the other three are known ; 
the fix parts being the three fides and the three angles ;) 
excepting, however, when the three angles are given; for 
in this cafe the proportion only of the three fides may be 
found ; but not their aGiual lengths. 
Vhen an inacceffible ane is to be determined by tri- 
gonometry, the method is to meafure a line or bafe upon 
any convenient place, and to obferve the angles which the 
imaginary lines, ee to be drawn from the extremities 
of that bafe line to a point or ohje& at the extremity 0 
the diftance euch make with the bafe; for in that cafe 
we have two anyles, and one fide of a elon whence we 
find by calculation the lengths of the other fides, one of 
which is the diltance fought. 
line upo 
ation ; for in that cafe, the objcé itfelf will be fuppofed to 
form the bafe of an ifofceles, or of a right-angled triangle ; 
and it will be only neceffary to meafure the angle whict 
that object fubtends at the place of obfervation. The 
ftance of an objeét being known, the fize of the obje& aay 
be eafily deter mined bv on y meafuring the angle which it 
fubtends. See Tri 
the cecum as for meafuring diftances from a. 
vance by which the angle which the direétion of a diftan 
object makes with that bafe line at each extremity of i. 
may be meafured. But as fuch initruments cannot be made 
n inconvenient large fize, the bafe line which they con- 
h 
inftruments isa furnifh a refult fufficiently exaé, a leat 
for certain purpofes 
e moit complete inftruments of this kind are furnifhed 
with “i or more {peculums, (fomewhat in the manner of 
Hadley’s quadrant,) for mesnag the difference of the an- 
gles at once. Upon this plan feveral inftruments have been 
contrived and offered to the public by various writers. One 
of the mo Promifing, though not the moft compa, is de- 
{cribed in “ Gower’s Supplement to the Practical Seaman- 
fhip.”” ta i 
of any inftrument of this kind, uite free from 
ftrong objeétions, we fhall only fubjoin a general idea of the 
oo upon which fuch an inftrument may be conftru&- 
ed ; e ufe of thofe perfons who may be defirous of — 
ociae thei aucnan upon the nies ion roreae-ais of 
that conftru 
The flowy: a are fuggefted by William Pitt, eq. 
in the fecond volume of the Repertor 
oO 
» (fig. 10.) 18 the obje&, whofe diftance 3 required. 
ABCDE i is the inftrument in plano; BC a tele 
placed reed parallel to the fide A E. 
circle whofe centre is at A, accurately divided from E, in: 
degrees, &c. is an index, moveable on the centre A, 
with a no pius des rae 
fions of th 
f, the more ea he 
8 Gieebie a 
theodolite, and furnifhed with {pirit levels, to adjuft it'to: 
an horizontal pofition. The inftrument.being placed in fuch- 
pofition, the telefcope BC mult be brought upon the ob=- 
je& O, or rather upon fome particular point or-fide thereof} - 
whet 
