7. " The time being known at any giv en place, as suppose London, to find what hour it is in any other pa: t of the world." Bring the given place, London, to the me ridian, and set the index to the given hour; then turn the globe till the other place come to the meridian, and look at what hour the index points, which will be the time sought.
S. " To find the sun's place in the ecliptic, and also on the globe, at any giv en time." Look into the calendar on the wooden horizon for the month and day of the month proposed, and immediately op posite stands the sign and degree which the sun is in on that day. Then, in the ecliptic drawn upon the globe, look for the same sign and degree, and that will be the place of the sun required.
9. " To find at what place on the earth the sun is vertical, at a given moment of time at another place, as suppose Lon don." Find the sun's place on the globe by the last problem, and turn the globe about till that place come to the meridian, and note the degree of the meridian just over it. Then turn the globe till the giv en place, London, come to the meridian, and set the index to the'given moment of time. Lastly, turn the globe till the index points to twelve at noon ; then the place of the earth, or globe, which stands under the before noted degree, has the sun at that moment in the zenith.
10. " To find how long the sun shines, without setting, in any given place in the frigid zones." Subtract the degrees of latitude of the given place from ninety, which gives the complement of the lati tude, and count the number of this com plement upon the meridian fromthe equa tor towards the pole, marking that point of the meridian ; then turn the globe round,and carefully observe what two de grees of the ecliptic pass exactly under the point marked on the meridian. Then look for the same degrees of the ecliptic on the wooden horizon, and just oppo site to them stand the months and days of the months corresponding, and between which two days the sun never sets in that latitude.
If the beginning and end of the longest night be required, or the period of time in which the sun never rises at that place; count the same compleMent of latitude towards the south or farthest pole, and then the rest of the work will be the same in all respects as above.
Note, that this solution is independent of the horizontal refraction of the sun, which raises him rather more than half a degree higher, by that means making the day so Much longer, and the night the shorter ; therefore, in this case, set the mark on the meridian half a degree high er up towards the north pole than what the complement of latitude gives ; then proceed with it as before, and the more exact time and length of the longest day and night will be found 11. " A place being given in the torrid
zone, to find on what two days of the year the sun is vertical at that place." Turn the globe about till the given place come to the meridian, and note the degree of the meridian it comes under. Next turn the globe round again, and note the two points of the ecliptic passing under that degree of the meridian. Lastly, by the wooden horizon, find on what days the sun is in those two points of the ecliptic ; and on these days he will be vertical to the given place.
12. " To find those places in the torrid zone to which the sun is vertical on a giv en day." Having found the sun's place in the ecliptic, as in the eighth problem, turn the globe to bring the same point of the ecliptic on the globe to the meridian; then again turn the globe round, and note all the places which pass under that point of the meridian ; which will be the places sought.
After the same manner may be found what people are ascii for any given day. And also to what place of the earth, the moon, or any other planet, is vertical on a given day ; finding the place of the pla net on the globe by means of its right ascension and declination, like finding a place from its longitude and latitude giv en.
13. " To rectify the globe for the lati tude of any place." By sliding the brass meridian in its groove, elevate the pole as far above the horizon as is equal to the la titude of the place ; so for London, raise the north pole fifty-one and a half degrees above the wooden horizon : then turn the globe on its axis till the place, as London, come to the meridian, and there set the index to twelve at noon. Then is the place exactly on the vertez, or top point of the globe, at ninety degrees every way round from the wooden horizon, which represents the horizon of the place. And if the frame of the globe be turned about till the compass needle point to twenty two and a half degrees, or two points west of the north point (because the variation of the magnetic needle is nearly twenty two and a half degrees west), so shall the globe then stand in the exact position of the earth, with its axis pointing to the north pole.