The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . lnss to nny Ioiut inthe fielil of view. A new lealiue in this instiuincnl is tlic i>;rniat the lower end of the i> a\s, wliere an a^islaut am vi, w il,...hour cii\.!e by one eye-pieee aiij tlie tiecliuation circle byjSDOthcr (looking np the jicrforated polar a.\is), and(where he can also set the telescope to any hour angl«Inf one wheel, or to ;iny dccliDatiou
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . lnss to nny Ioiut inthe fielil of view. A new lealiue in this instiuincnl is tlic i>;rniat the lower end of the i> a\s, wliere an a^islaut am vi, w il,...hour cii\.!e by one eye-pieee aiij tlie tiecliuation circle byjSDOthcr (looking np the jicrforated polar a.\is), and(where he can also set the telescope to any hour angl«Inf one wheel, or to ;iny dccliDatiou by a second, withtoe greatest rise. The observer at the e\e endcan also lead otf the hour and ilccliuation circlesand coniniunicate qn;ck or slow motions to thetelescope in right ascension and dtclina-tion by conveniently placed handles. Theeye end presents an appearance too com-(Hicated to be figured liere; it has a mi-cronteter and its illnininatiou for theposition circle, a micrometer head,and a bright or dark field, clampsin right ascension and declinationand quick and slow motion inthe :e, a tinder, ndcroscopesfor reading the hour and de- clination circles,an illuniin-»ted dial showing sidereal. Hi ^ . . refractoi?, pme and diiven by a galvanic current from the sideTeaTclockTand toonter weights which can be removed when a spectroscope or other heavy appliance is added. All these, although mating up an ap- nuently complicated apparatus, arc conveniently arranged, and are all necessary for the quick and easy working of so large -v an instniment. We have the authority of Otto Strave for stating that in practice they are ail that can be, desired. There is in this instrument a remarkably fel^ant method of relieving the friction of the - polar axis. Let AA (fig. 27) be a section of the polar axis; it is then easy to adjust the weight P of the circles, ic, attached to its ? lower end so that the centre of gravity ,X of the whole mo\-ing parts of the Instru
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Keywords: ., bookcentury1800, bookdecade1890, bookidencyclopedia, bookyear1892
