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XX. Obfervation of the Tranft of Mercury over the Sun's Difc , 
made at Louvain, in the Netherlands, May 3, 1786. By 
Nathaniel Pigott, Efq. F. R. S. 
Read June 15, 1786. 
Louvain, May 15, 1786. 
T HE tranfit of Mercury was to happen a few days after my 
arrival at this place from England. Although I brought 
no aftronomical inftruments with me, I wiftied to obferve 
this phenomenon ; and upon application to M. Thysbaert, 
Vrejident du College Royal , a very diftinguilhed Member of this 
Univerfity, he fupplied me, in the politeft manner, with the 
following inftruments, and a convenient place for the ob- 
fervation. He carried his attention to the moft trifling circum- 
ftances, in order to make my fituation, in every refpe£t, 
agreeable. The inftruments he provided me with were a 
Gregorian refle£lor of 21 inches focal length, with an aperture 
of 41 inches, the magnifying power of which I efteemed about 
70 or 80, with a good quadrant \ 8 inches radius, and a com- 
pound pendulum clock, fteadily fixed, beating dead feconds. 
Thefe inftruments were made in London, and ufed for the 
obfervatioa 
