C 10 5 3 
IV. An Account of a Method of dividing Astronomical and other 
Instruments , by ocular Inspection ; in which the usual Tools for 
graduating are not employed ; the whole Operation being so con- 
trived, that no Error can occur but what is chargeable to V ision , 
when assisted by the best optical Means of viewing and measur- 
ing minute Quantities. By Mr. Edward Troughton. Com- 
municated by the Astronomer Royal. 
Read February 2, 1809. 
It would ill become me, in addressing myself to the Members 
of this Society upon a subject which they are so well enabled 
to appreciate, to arrogate to myself more than may be as* 
signed as my due, for whatever of success may have been the 
result of my long continued endeavours, exerted in prosecut- 
ing towards perfection the dividing of Instruments immediately 
subservient to the purposes of Astronomy. A man very naturally 
will set a value upon a thing on which so much of his life 
has been expended ; and I shall readily, therefore, be par- 
doned for saying, that considering some attainments which I 
have made on this subject as too valuable to be lost, and 
being encouraged also by the degree of attention which the 
Royal Society has ever paid to practical subjects, I feel myself 
ambitious of presenting them to the public through what I 
deem the most respectable channel in the world. 
It was as early as the year 1775, being then apprentice to 
my brother, the late Mr. John Troughton, that the art of 
MDCCOIX. P 
