116 Friedrich Wilhelm August Argelander, 
also visited about this time by the cholera, which travelled 
over Europe; and Argelander took an opportunity, after 
leaving Abo, of revisiting his old home in Prussia, and renew- 
ing his personal intercourse with Bessel, In August, 1832 he 
took up his abode at Helsingfors, though the building of the 
Observatory was not yet finished. Observations commenced 
there in the following year; and in November, 1834 the 
meridian-circle was ready for use, the new observatory being 
also provided with a Munich refracter of 9 ft. focal length and 
63-in. aperture, observations with which commenced in Sep- 
tember, 1835. j 
Argelander devoted. himself principally to an extensive series 
of observations of the brighter cireumpolar stars, an 
William Herschel. 
His stay at Helsingfors was not of long duration. The 
