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XXVI. A Series of Obfervations on r and a Dfcovery of the 
Period of the Variation of the Light of the bright Star in the 
Tlead'of Mcdu.fa,. called Algol. In a Letter from John Good- 
ricke, Efq. to the Rev. Anthony Shepherd, D. D . F.R*S~ 
and Piumian Projefo-r at Cambridge. 
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Read May 15, 1783, 
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S I R, 
York, May 12, 1783. 
I TAKE the. liberty to tranfmit to you the following account 
of a very lingular variation in Algol or /3 Perfei, which you 
will oblige me by prefenting to the Royal Society, if you think 
it deferving that notice. All that has been hitherto known 
concerning the variation of this Par, as far as I can find after 
the mold diligent refearches, is comprifed in the following paf- 
fage in du iiamel’s Hi/loria Regia Scientiarum Academia liber 
IV. fell. 6. caput VIII. dc rebus APronomicis, aim. 1695, P* 
362. “ Id quoque tePatur D. montanari Pellam lucidiorem 
44 Medufae, diverlis annis, variae effe magnitudinis : nullam pene 
44 in ea mutationem potuit advertere D. maraldi annis 1692 
44 et 1693; fed anno 1.694 a'udla eld et imminuta inligniter, modo 
44 quarti, modo tertii, k modo fecundi ordin is Pella apparuit.” 
This, however curious, is only a very vague and general infor- 
mation ; but the following obfervations, lately made, exhibit 
a regular and periodical variation in that Par, of a nature hi- 
therto, 1 believe, unnoticed. 
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