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arguing, perhaps too far, from the level difpofition of the country tlircugh which the de- 
gree pafles. But the Honourable Mr. Henry Cavendilh has fince confidered this mat- 
ter more minutely; and having mathematically inveftigated feveral rules for finding the 
attraction of the inequalities of the Earth, has, upon probable fuppofjtions of the 
diflance and height cf the Allegany mountains from the degree meafured, and the 
depth and declivity of the Atlantic ocean, computed what alteration might be produced 
in the length of the degree, from the attraction of the faid hills, and the defect of at- 
traction of the Atlantic; and finds the degree may have been diminifhed by 60 r >r ioo 
toifes from thefe caufes. He has alfo found, by fimilar calculations, that the degrees 
meafured in Italy, and at the Cape of Good Hope, may be very fenfibly affected by 
the attraction of hills, and defect of the attraction of the Mediterranean Sea and Indian 
Ocean. 
The rules, which I ufed in calculating the ratio of the equatorial diameter to the po- 
lar axis, from the North American degree, compared with thofe meafured in Peru and 
Laplandy, are thofe given by Mr. John Robertfon, Librarian to the Royal Society, in 
his Elements of Navigation, p. 597 , as deduced by him from Dr. Lcherland’s Geo- 
metrical Analyfis of the problem, which he has alfo given to the public in the fame 
place, together with fome other problems depending upon it, which were neceflary to 
complete the fubjedl. 
XLIII. AJlro- 
