Mr. Groombridge’s Observations , &c. igt 
so many observations by one person, it will appear to have 
been impracticable. I remain. 
Dear Sir, 
Your obliged and very obedient servant, 
STEPHEN GROOMBRIDGE. 
To the Rev. Dr. Maskelyne , 
Astronomer Royal, 4’C. Sf-c. 
When I had fixed my four feet transit circle, made by 
Troughton, it was my intention to make observations of a 
sufficient number of circumpolar stars, at different altitudes, 
to ascertain the latitude of my observatory with the greater 
precision ; and also to endeavour to settle the true quantity 
of refraction : especially as my instrument was better adapted 
for that purpose, both from the construction and convenient 
size thereof, than those which had been heretofore made. 
Being fixed on stone piers, it is not so liable to partial expan- 
sion, as those instruments which are supported on brass 
frames : and having both sides divided, with two microscopes 
to each face ; the same observation has the advantage of four 
made with a quadrant. I have also contrived, by means of 
sliding shutters in the roof, to prevent the rays of the sun 
from falling on any part, excepting on the object glass. By 
these means I flatter myself that, the observations having 
been made with great care and attention, the result will prove 
both satisfactory and useful. 
Having proposed to myself the above course of observa- 
tions, 1 selected the fifty stars contained in the first table for 
that purpose, the observations of which, exceed in number 
C C 2 
