14 The true time employed by each turn of the latter wheel 60 may therefore be thus ascertained ; d.
as 4330.72916: 4325.22916:: 51:5.493014. Hence 5 493014 must be taken instead of 51 days, as the period in which the four contemporary wheels revolve, which arc made fast to the common arbor of the wheel 60, just mentioned ; and if the acceleration or difference .006986 be multiplied by the days and parts of Jupiter's period above stated, the product will be 51 days, the whole amount of the acceleration. The four wheels, 90, 51, 46, and 20, or the common arbor of wheel 60, drive their corresponding wheels 29, 33, 60, and 61. fixed to as many separate tubes, in the respective periods of the four satellites, and the arms carried by those tubes perform their revolutions round Jupiter whenever the weekly ar bor is made to revolve. The distances of the satellites from Jupiter are taken from a scale of which his diameter is the unit, and a small lamp, substituted for the earth, will project their shadows on a paper screen made fast to a slender bar that is adjustable on the lower end of Ju piter's stem. The time of Jupiter's meridian passage is, moreover, shown on an horary dial surrounding the weekly arbor, by means both simple and accurate : a pinion 14 driven by Jupiter's wheel 166, in a solar year, like the one we before described as carrying the sidereal plate, has a tube revolving round the weekly arbor G, which carries an annual index V round the horary dial NV, which dial is made to revolve within the weekly rim in Jupiter's period by means of a second wheel .53, which, by its con
nexion with Jupiter's 53, turns in Jupiter's period ; the annual hand, therefore, passes over Jupiter's dial in his H synodic period ; and when the hand is put to XXIV at the time of Jupiter's conjunction, the distance in time of the planet from the sun, or the time of his southing, on any subsequent day will be pointed out on this dial, while the day of the week is indicated on the divided rim surround ing it.
It would enlarge our article far beyond our prescribed bounds, if we were to enter into a detail of all the variety of phenomena that may be illustrated, and problems that may be worked by this comprehensive machine, when in a proper state of rectification, with a three inch terres trial globe and its appendages, which were described in our preceding account of the " Tellurian and Lunarium united." This machine is properly what Benjamin Mar tin denominated one of his less accurate and less compre hensive machines, " a Microcosm," or world in miniature. We shall conclude our description by giving such a Table of Dimensions of this machine, as will enable any clock maker to undertake and accomplish its construction,