the 'Trigonometrical Operation. 
*35 
SECTION SECOND. 
General Defer iption of the great infrument with which the angles 
in the recent trigonometrical operation , were obferved ; f dewing 
alfo its various adjufments for practice. Reference to be had to 
Plate III. a general view of the entire machine ; Plate IV. a 
plan and two fedlions ; Plate V. various parts reprefented t® 
large feales ; and Plate VI. the microfcopes and eyepieces*. 
Article I. Preamble . 
IN endeavouring to deferibe the curious instrument made ufe 
of for obferving the angles in the recent trigonometrical ope- 
ration, it has been judged beft to confine ourfelves to the prin- 
cipal parts, without entering into any detail of the minutiae i 
for even to have mentioned thefe,. with the almoft infinite 
number of little ferews that Serve to unite them into one entire 
machine, which could only have been done by references to a 
multitude of great and fmall Roman and Greek characters,, 
would have been a difgufting labour. By the help of the four 
plates which this defeription refers to, and which have been 
executed with great care, that fewer words might Suffice, it is 
hoped, that the inftrument may be underftood by two claffes 
of people for whom it is chiefly intended ; firft, by thofe who* 
being poflefled of fuch a machine would wifli to make them- 
Selves matters of its ufe; and, Secondly,, by fuch ingenious 
artifts as would attempt to conftruCt fuch another; tor thefe 
laft, in particular, the parts that are of brafs, of bell-metal, 
or: 
