[ 7?6 ] 
to the Situation and time (allowing for the difference 
between the meridians of Dublin and Hornfey), it 
being nearly half an hour paft ten at Dublin when 
eleven here, makes it very probable, that it was one 
and the fame meteor ; which, if fo, is a proof, that 
its height in the atmofphere muff be very consider- 
able. I am, 
S I R, 
Your obliged humble Servant, 
William Hirft. 
: - 
XGII. A Letter from Monfieur Clairaut, 
Member of the Royal Academy of Sciences 
at Paris, and F. R. S. to Thomas Birch, 
D. D. Secret. R. S. containing a Compa- 
rifon bet r coee?i the Notions of Wl. de Cour- 
tivron a?id Mr. Melvil, concerning the Dif- 
ference of Ref Tangibility of the Rays of 
Light. 
Read July 4, A S I was pending the laft volume of 
/ \ the Philofophical Tranfadtions, I 
fell upon a memoir of Mr. Melvil, the fubjedt of 
which having been handled in a book, that I pre- 
sented Some time ago to the Royal Society, from a 
friend of mine, and written upon a matter, which I 
had 
