50 Question addressed to the Rev. J. Grooby. 
ployed in common arithmetic, have been equally augmented, and 
the augment of each quantity, in this case, is = 3a +1; but 
the difference between these augmented quantities is, as I have 
shown, the same as it would have been between the original pro- 
posed quantities. Iam sir, very respectfully, 
Your obedient humble servant, 
PauL Newron. 
XII. A Question addressed to the Rev. J. Groosy, respecting 
the Tables employed by him in calculating the Corrections of 
Dr. MaskELynx’s 36 Stars. By A CorRESPONDENT. 
To Dr. Tilloch. 
Sir,—Wrar you permit me, through your Journal, to ask your 
correspondent Mr. Grooby, what tables of Professor Bessel’s he 
makes use of in the calculation of the Corrections of Maskelyne’s 
Stars. I have not heard of any except those annexed to his Ob- 
servations, and | do not find that they give the same corrections 
as Mr. G. uses, though very neartoit. It is a circumstance not 
generally known, perhaps, to your astronomical readers, that the 
Professor himself does not use his own tables in reducing his ob- 
servations ; as any one may satisfy himself, if he will only take 
the trouble of reducing a few of the transits he has published, and 
comparing the results with the corrected Right Ascension given 
by the Professor himself. I have calculated some hundreds, and 
never found one agree: hence I had supposed that I must have 
mistaken Lis mode of calculation, particularly as he has given no 
example of his method of using his tables. But in his .4s¢rono- 
mie Fundamenta he has given examples, and, what is most ex- 
traordinary, not one of the corrections in those examples agrees, 
with the one given by the table. Give me leave to notice one 
more particularly,—and I will take the first., Where the cor- 
rection of « Lyr@ is required on the 13th of December 1756. 
Adding, as the two preliminary tables direct, 1.56, I am to look 
out in Table Ist for the correction answering to December 14. 56. 
Now opposite to December 6. I find +0.273, and opposite to 
December 16. +0.246, difference ,027. I say therefore,—As 
10 days is to ,027, so is 8.56 to ,023; which, as the numbers 
are diminishing, is to be subtracted from +0.273, and give 
+0.250 for the correction ; but in the example it is +0.247. 
This, it is true, is no great difference ; but small as it is, it ought 
not to be, and Mr. Grooby will perhaps find some difficulty in 
accounting for it, as well as in maintaining his opinion, that 
M. Bessel’s Tables are the most correct yet published. 
I am sir, your obedient servant, 
OxBsERVER. 
XIII. On 
