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The N.Z. Journal of Science and Technology. 
[May 
graduated in hours of mean time from noon through xii, xm (i), xiv ( 11 ), 
&c., uniformly clockwise to xxiv, or noon ; the inner circle B 2 graduated 
in degrees of longitude from 0°, opposite noon, uniformly counter-clock¬ 
wise through east longitudes and clockwise through west longitudes to 
180°, opposite xii. This ring is furnished with a clamp. (The longitude 
circle is not an essential part of the planisphere, but it enables one to set 
the instrument for the time of any meridian, not necessarily that of the 
place of observation). 
C. The Horizon (the inner part of fig. 2).—This consists of a disc 
containing an oval aperture whose boundary is the projection of the 
horizon. This aperture is covered with a celluloid window on which are 
traced two systems of curves, the verticals passing through the zenith and 
showing the azimuths, and the almucantars showing the altitudes. The 
margin of the aperture is marked with the points of the compass. Round 
the edge of the disc are two graduated circles : the outer circle C 2 
graduated in degrees of longitude as in B 2 , 0° being opposite the north 
point, which is the point of the horizon nearest the margin ; the inner 
circle graduated in hours of local mean time as in B t . 
All the circles are pivoted at a common centre. Fig. 2 is to be super¬ 
posed upon fig. 1 so that the date circle A 1 is outermost; then the 
standard-time circle B x and longitude circle B 2 on the ring, and next the 
longitude circle C 2 and the local-time circle C x on the horizon-disc, fall 
