|6S OF THE LATITUDE AND LONGITUDE-

meridians, the clocks of. those places will showthe beginning or end to be at different times,according to their situations. An eclipse of themoon, therefore, being observed from any twoplaces whatever, will furnish us with the meansof discovering the longitude of those places. If,for instance, the time-pieces of one place, fliowthe beginning of the eclipse to be at twelveo’clock, and the time-pieces of the other, at one,the difference of longitude between these twoplaces will evidently be fifteen degrees; and soon, in the same proportion.

It will be necessary to remark, however, thatthese observations must be compared with thosemade at a place whose longitude is known, be-fore we can determine the meridian under whichwe are situated. So that if I am upon someunknown part of the globe, the longitude ofwhich I am desirous of discovering, and havean opportunity of making observations on aneclipse of the moon, these observations will beof no service to me, unless I can compare themwith those made at London, or some other placewhose situation is known. Some farther assist-ance is therefore requisite; for if I am obligedto wait till I return to London, it would notanswer my purpose, as I want to inform myselfupon the spot.

, To obtain this information, we muff have re-course to the theory of the moon, which is now

so