An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

A S't'RONtf)tO[cA NTRlfI t}.iNTS. 51
strcnlgthl, Tlhe two ends of the axis xest on two firm spports,
as pillars of stone, for examplle, usually built up from tlhe
ground, and so related to the )buillintg as to be as freet as possible
firom till eroaitation. -In figurle 14, Al) represents the telescope,
t, W, umassive stone pillars supp)orting the lorizonlta axis,
belnathl u li cl is seel a spirit-level (whichl: is usced to brintt
the axis to a horizontal position), antd nC af vertical circle graduated into degrees and min tes. T'his circle seCrves the 1llrposm of placing theo instruml ntt t at afny req(uired.altitude ot>r idistance fr1om tlte zenith, and of course for determinirng altitudes
and zenith distances.
O t...
1 22. Variou0s MIethods are descrtibed in \ortks on prla tical
astroomlrly, for placing the T"lratnsit Ilstruttmient accurtately in the
rneridian. ThXe following method, bly obserTvatiolns on tle lfolcitfar, may serve RS a example. If the instrument be, directed
towtards the north sttar, and sio. tadustedt: tlat the'tar Alioth (the
first,in thle tail of the Grea- t B3eatr) alnd tlte )olestar are both in
the s8am1e 1 vertical circle, the forlmtler bclowt the.pole a<tlnd the latter above it, the ins.sltrumlent will be ura-nrly in fthe Plhanle of tlhe
meridian. To adj\ust it m-10e exactly, com1pare, thle timel Ocen