But the idea of a planetarium, somewhat similar to the Rittenhouse-orrery, seems to have been conceived by Huygens, who died in 1695. A collection of this celebrated philosopher’s works was printed at Leyden in the year 1724 and 1728: and in these will be found the description of a planetarium; “a machine” (says Lalande, in speaking of the one contemplated by Huygens,) “which represents, by wheel-work, the revolutions of the planets around the sun and of the moon around the earth, in their durations and natural dimensions; with their excentricities, their inequalities, and their inclinations towards the ecliptic.” See Lalande’s _Astron._ Footnote 136: Mr. Jefferson remarks, in his _Notes on Virginia_, that “Mr. Rittenhouse’s model of the planetary system has the plagiary appellation of an Orrery.” This was, undoubtedly, a plagiary name, in its relation to Graham’s Planetarium, of which Lord Orrery was the supposed inventor: but the charge of plagiarism does not properly apply to the same name, when bestowed by Mr. Rittenhouse himself, on the grand machine of his own invention and construction. How improper soever this name may have been in its first application to a planetarium, it has since been generally applied to similar machines; and it has thus acquired an appropriate signification in relation to them. Mr. Rittenhouse did not choose to depart from the appellation in common use, in naming a machine for surpassing, in ingenuity of contrivance, accuracy and utility, any thing of the kind ever before constructed; yet, in all those points of excellence, he was the inventor of that admirable machine, which has been generally denominated, by others, “the Rittenhouse Orrery.” -----