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Mr. Euler was also a supporter of the 
theory of Dr. Halley, supposing the earth 
to be hollow, with a nucleus included : he 
only differed as to the nature of this nu¬ 
cleus. Dr. Halley supposed that the nu¬ 
cleus contained within the earth was com¬ 
posed of the same sort of matter as the 
earth itself; but Mr. Euler believed that 
the nucleus was a luminous body, formed 
for the purpose of maintaining the inter¬ 
nal heat of the globe, and giving light to 
the hollow parts of the earth, which he 
supposes well inhabited, equally with the 
exterior surface. He also fancied that this 
solar nucleus in the hollow of the earth, 
had no rotary motion, but that the earth 
revolved round it. 
The theory of Mr. Euler, therefore, 
bears a stronger resemblance to the theory 
of Capt. Symmes than the hypothesis of 
Dr. Halley. Capt. Symmes differs from 
Mr. Euler in supposing an opening to¬ 
wards each pole of the earth. This is the 
only circumstance which appears new in 
the theory of Capt. Symmes, as the rest 
of his theory has been frequently discus¬ 
sed and examined by many of the first 
mathematicians,and has still several sup¬ 
porters among the learned of Europe. 
We have been always more astonished 
at the ridicule which has been cast upon 
the hypothesis of Capt. Symmes, than 
even with his proposition of exploring the 
regions towards the North pole. We of¬ 
fer these remarks not as believers or sup¬ 
porters of the project of Capt. Symmes, 
buc with a view of showing that the ideas 
which he has ottered to the public merit 
