Celestial and 'Terrejlrial Globes. 133

every year j the first is the autumnal, thesecond the vernal, equinox.

At these times the fun appears to rife andset at the same instant to all places in thesame meridian.

But their twilight is longer as their situa-tion is nearer to either pole; in so muchthat within 18 degrees of the poles, theirtwilight is 12 hours, consequently there isno dark night in those places at the timesof equinox: when at the same time thoseplaces under the equator have only one hourand 12 minutes twilight; so that their arti-ficial day is about 14 h. 24 mm. at these twoseasons of the year.

Thus, if London and Mundford on theGold Coast, be brought to the strong brassmeridian, the graduated fide of which is inthis cafe the horary index; (tho’ in othercafes the hour index is to be set to that XIIwhich is most elevated 5) if then they bebrought to the west side of the broad papercircle, the index will point to VI o’clockfor sun-rising, and to VI for sun-setting,when these places are brought to theeastern side.

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Also,