[ J 9* 1 
iron, in the memoirs of the Royal Academy of 
Sciences for 1 7 1 7, to afcribe this contrivance of the 
micrometer to M. Auzout, in conjunction with M. 
Picard j alleging, for proof, an extraCt of a letter, 
dated Dec. 28, 1 666, from M. Auzout to M. Olden- 
burg, and printed in Phil Tra?if. N° 2 ty Several 
others have fince copied M. de la Hire’s aflertion, 
and laft of all, M. Bouguer, in the memoirs of the 
Royal Academy of Sciences for 1748, lately pub- 
lifh’d, wherein he defcribes an inftrument, which he 
calls an heliometer ; the contrivance whereof feems 
in every refpeCt the fame as that fent about ten years 
ago to the Royal Society, by Servington Savery, Efqj. 
I have now before me the copy of a letter of Mr. 
Gafcoigne to Mr. Oughtred, which I made myfelf 
from the original, written in 1640-1 j which original 
was in the poffeflion of the late William Jones, Efq ; 
E. R. S. and is now in the library of the right 
honourable the Earl of Macclesfield. It confifts of 
feveral fheets of paper, all about his invention for 
meafuring fmall angles to feconds j where he not 
only gives the geometrical and optical principles of his 
contrivance, and the conftruCtion of the inftrument, , 
but alfo a feries of obfervations actually taken there- 
with i fome of which I fhall tranfcribe. 
1640 Aug. y. Jupiter’s diameter . 
Mars’s 
Dec. 24. Mars’s 
Venus’s 
/ if 
• o yi 
. o 38 
. o- 2y 
. o 27 
3640 Aug. 27 Moon’s femidiam. iy 17 
Sept. 19 . • • . 1 7 1 1 
h. 8 p. m. 
1640 
! 
