How important soever, in relation to astronomy, the phænomena observed by Mayer may be, the honour of first discovering them certainly belongs to him. Mr. Rittenhouse was not the discoverer: nor had he ever access to so complete and expensive an astronomical apparatus, as that used by Mayer on the occasion, and with which he was furnished by means of princely munificence. But all candid men of science will, nevertheless, be disposed to allow the American Astronomer no inconsiderable share of merit for the early “presage,” which his deep-discerning and vastly comprehensive mind enabled him to suggest, of some such future discoveries. The writer of these memoirs deemed it his duty to do justice to the memory of the subject of them, by giving publicity to these interesting circumstances; and the performance of this duty is the more gratifying to the writer, because he alone possesses a knowledge of all the facts he has stated, concerning them. The late discoveries of Dr. Herschel, among the fixed stars, in addition to those previously made by Mr. Mayer, have in a greater degree realised the expectations which were formed, many years before either, by our Astronomer; such, indeed, as are almost entitled to the character of prescient annunciations, respecting that portion of the heavens which should, some time or other, be the scene of the most important astronomical discoveries. According to Herschel, the Milky Way is an immense nebula, near one of the sides of which, is placed the solar system; and he imagines, that each nebula, of which he had observed more than nine hundred, consists of a group of suns, with their attendant planets! Mr. Rittenhouse never possessed the means of acquiring such stupendous and costly telescopes, as those used by Herschel, for the purpose of exploring the heavens. But the penetrating genius of our countryman seems to have contemplated, by anticipation, the actual existence of those sublime phænomena, some of which the vastly superior instruments of the Germano-Anglican Astronomer have since manifested; when, in language apparently prophetic, but certainly dictated by the most exalted pre-conceptions of the grandeur of celestial objects which were yet undiscovered, the American Philosopher observes, as he does in his Oration,—that “all yonder stars innumerable, with their dependencies, may perhaps compose but the leaf of a flower in the Creator’s garden, or a single pillar in the immense building of the Divine Architect.” Well might he exclaim, with rapturous extacy, after so beautiful and sublime a reflection,—“Here is ample provision made for the all-grasping mind of man!”