C 190 3 
X. Observations on Atmospherical Refraction as it affects astro- 
nomical Observations ; in a Letter from S. Groombridge, Esq. 
to the Rev. Nevil Maskelyne, D. D. F. R. S. Astronomer 
Royal. Communicated by the Astronomer Royal . 
Read March 28th, 1810. 
DEAR Sir, BlacUieath, 22nd January, 1810. 
The great advantages we derive from the labours and 
writings of those learned men, who have preceded us ; the 
profound researches in physical astronomy by the mathema- 
ticians of the last century ; and the improvements in the con- 
struction of instruments, effected by the ingenuity of our 
modern artists : these circumstances should stimulate all those 
who have inclination and opportunity, to the endeavour of 
contributing to the common stock of knowledge. I beg leave 
to add my tribute of admiration to the general voice, for the 
large share you, Sir, have taken in the promotion of science, 
not only by your learned publications, but also by the liberal 
encouragement and assistance you have given to those who 
have been honoured with your acquaintance. I am, therefore, 
induced to commit to your protection the inclosed paper, ac- 
knowledging myself indebted to your friendly communica- 
tions for much useful information. I could have wished the 
task had been performed at an earlier period ; but as you are 
well acquainted with the labour required in the reduction of 
