[ 338 3 
later, but how many I do not now remember. 
Mr. Anderfon, F.R.S. fitted up a clock and appa- 
ratus in the college fteeple ; his clock was regulated 
as above, by fignals from the obfervatory j he ob- 
ferved the tranfit with a large refiedfor, and his aflift- 
ants obferved with refractors: they were all of them 
uncertain about the external contaCt, owing to the . 
hate of the atmofphere, and a tremor given to the 
fteeple by the wind j but none of their other obfer- 
vations varied, above three feconds, from my own,' as 
related above. 
O t It 
Latitude of the obfervatory 55 51 32 
Longitude by correfpondlngl of time from Greenwich W. 
oblervations J ' 
I am. Sir, 
with great efteem, 
Your moft obedient fervant, 
Alexander Wilfon. 
I have obferved, during the courfe of this year, fe- 
veral times, the Aurora Borealis form itfelf into an 
arch, 20 or 30 degrees above the horizon, which con- 
tinued permanent for fome time ; and in this cafe the 
vertex of the arch appeared always to be weft from 
north, by about the variation of the needle in'19 or 
20 degrees. Whether or not jt is always fo, I cannot 
yet fay. 
XLIV. An 
