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^V 



ASTRONOMICAL PAPERS 



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Mr. Horfley and Mr, Dunn obferved with me in the 

 great room; Mr. Plitchins and Mr. Hirft, in the eaftern 

 fummer-honfe; and Mr. Dollond' and Mr. Nairne in the 

 weftern fummer-houfe; by three clocks placed in the re- 

 fpcdive rooms, which were compared with the clock in 

 the tranfit room, before the external conta£l, and again 

 after the internal contact was part; whence the times of the 

 obfervations, as noted by the clocks, were reduced to the 

 time of the tranfit clock, and thence to apparent time. 



Their obfervations, together with my own, are given 

 n the following table, as reduced to apparent time.- 



I 



rfii **■ 



N. Milkclyne 

 M. HJtchins 

 W. Hira 

 J. Horfley 

 S. Dunn 

 P. Dollond 

 K. N;iii'ne i 



External 

 contact. 



RcguUir cir- 



cunii'crcncesiu 



coiUadl. 



h. m. ice. 



7 

 7 

 1 

 7 

 1 

 7 

 7 



10 

 10 



n 



10 



lo 

 II 

 II 



58 



54 

 II 



^4 



37 

 19 



30 



h. 



Ul. 



fee. 



7 



%% 



31 



7 



28- 



47 



7 



%% 



15 



7 



39 



z8 





rhrcatl of light 

 complcatcd, 

 or^ tnc inter- 

 nal contadl. 



«M* 



h. 



7 

 7 

 7 

 7 

 7 

 7 

 7 



m; 



29 



29 



fee. 



23 



57 

 18 



29 48 

 29 20 



%() %o 



Tclcfcopcs made ufe of. 



% feet reflt(5lor. 

 6 feet rcflcdlor. 

 % feet refleiflor. 

 10 feet achromatic. 

 3f feet achromatic. 

 3 1 fcL't achromiitic 

 2 feet reiletSlor. 



Magni- 

 fying 

 power. 



140 

 90 



SS 



50 

 140 



150 



120 



Mr. DoUond and Mr. Nairne ufed telefcopes of tbeir 

 own conftruction;. but tbey did not wait 'till the thread o£ 

 light was formed at the internal contaft, but noted the 

 time, when they judged it was juft ready to be formed. The 

 three and an half achromatic telefcopes were thofe made 

 with three objed glaffes. 



The differences between the different obfervations feem 

 pretty confiderable, and greater than I expected, confide- 

 ring tbat all the telefcopes may be reckoned pretty nearly 

 equal excepting the fix feet refle£tor, which is muchfupe- 

 rior to them all; and to its greater excellence and diffmd- 

 nefs I principally attribute the difference of 26^', by which 

 Mn Hitchins faw the internal contad before me; as I can 

 depend upon his obfervations. Poffibly the greatnefs of 

 the differences might arife from the low altitude of the 

 Sun and Venus; and then the like differences wouWnot 



be fo much to be feared in places where the obfervation 



may 



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