. Astronomy for high schools and colleges . THE TRANSIT INSTRUMENT. 79 exact second by the clock (which is always near the ob-server, beating seconds audibly), this second must be writ-ten down as the time of the transit over this thread. Asa rule, however, the transit cannot occur on the exactbeat of the clock, but at tlie seventeenth second (for exam-ple) the star may be on tlie right of the wire, say at a ;while at the eighteenth secondit will have passed this wire andmay be at h. If the distance ofa from the wire is six tenths ofthe distance ah, then the timeof transit is to be recorded as
. Astronomy for high schools and colleges . THE TRANSIT INSTRUMENT. 79 exact second by the clock (which is always near the ob-server, beating seconds audibly), this second must be writ-ten down as the time of the transit over this thread. Asa rule, however, the transit cannot occur on the exactbeat of the clock, but at tlie seventeenth second (for exam-ple) the star may be on tlie right of the wire, say at a ;while at the eighteenth secondit will have passed this wire andmay be at h. If the distance ofa from the wire is six tenths ofthe distance ah, then the timeof transit is to be recorded as —hours — minutes (to be taken ^^^^^^^^^from the clock-face), and seven-teen and six tenths seconds / and in this way the transitover each wire is observed. This is the method of ** eye-and-ear observation, the basis of such work as we havedescribed, and it is so called from the part which both theeye and the ear play in the appreciation of intervals of ear catches the beat of the clock, the eye fixes the placeof the star at 6
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