kct.it.] DISSERTATION SECOND. 163 



The establishment of astronomical observatories, as na- 

 tional or royal works, is connected in Europe with the in- 

 stitution of scientifick or philosophical societies. The 

 necessity of the former was, indeed, even more apparent 

 than that of the latter. A science, which has the heavenly 

 bodies for its objects, ought, as far as possible, to be ex- 

 empted from the vicissitudes of the earth. As it gains 

 strength but slowly, and requires ages to complete its dis- 

 coveries, the plan of observation must not be limited by the 

 life of the individual who pursues it, but must be followed 

 out in the same place, year after year, to an unlimited 

 extent. A perception of this trulh, however indistinct, 

 seems, from the earliest times, to have suggested the utili- 

 ty of observatories to those sovereigns who patronised 

 astronomy, whether they looked to that science for real or 

 imaginary instruction. The circle of Osymandias is the 

 subject erf one of the most ancient traditions in science, and 

 has preserved the name of a prince which otherwise would 

 have been entirely unknown. A building, dedicated to 

 astronomy, made a conspicuous part of the magnificent es- 

 tablishment of the school of Alexandria. During the middle 

 ages, in the course of the migrations of science toward the 

 east, sumptuous buildings, furnished with astronomical in- 

 struments, rose successively in the plains of Mesopotamia, 

 and among the mountains of Tartary. An observatory in 

 the gardens of the Caliph of Bagdat contained a quadrant 

 of fifteen cubits l in radius, and a sextant of forty. 2 Instru- 

 ments of a still larger size distinguished the observatory of 

 Samarcande, and the accounts would seem incredible, if 

 the ruins of Benares did not, at this moment, attest the 

 reality of similar constructions. 



1 Twenty-two feet three inches. 



2 Sixty feet five inches. 



