The building is in two stories--the upper of brick, with freestone quoins, impost and window and door dressings, rests upon a rusticated basement of freestone, six feet high. The style adopted is the modern Italian, of which it is a very excellent specimen. The building has been completed some time; but, in consequence of the size of the instruments now procured being greater than that originally contemplated, sundry alterations were required in the Transit and Meridian Circle rooms. These consist of the semi-circular projections already mentioned, and which, by varying the outlines of the building, will add greatly to its beauty and picturesqueness. The piers for the Meridian Circle and Transit have, after careful investigation, been procured from the Lockport quarries. The great density and uniformity of the structure of the stone, and the facility with which such large masses as are required for this purpose can be procured there, have induced the selection of these quarries. The stones will weigh from six and a half to eight tons each. The main building was erected from the drawings of Messrs. Woollett and Ogden, Architects, Albany; the additions and the machinery have been designed by Mr. W. Hodgins, Civil Engineer; and the latter is now being constructed under his superintendence, in a very superior manner, at the iron works of Messrs. Pruyn and Lansing, Albany. The entire building is a tasteful and elegant structure, much superior in architectural character to any other in America devoted to a similar purpose. ORATION. FELLOW CITIZENS OF ALBANY:-- Assembled as we are, under your auspices, in this ancient and hospitable city, for an object indicative of a highly-advanced stage of scientific culture, it is natural, in the first place, to cast a historical glance at the past. It seems almost to surpass belief, though an unquestioned fact, that more than a century should have passed away, after Cabot had discovered the coast of North America for England, before any knowledge was gained of the noble river on which your city stands, and which was destined by Providence to determine, in after times, the position of the commercial metropolis of the Continent. It is true that Verazzano, a bold and sagacious Florentine navigator, in the service of France, had entered the Narrows in 1524, which he describes as a very large river, deep at its mouth, which forced its way through steep hills to the sea; but though he, like all the naval adventurers of that age, was sailing westward in search of a shorter passage to India, he left this part of the coast without any attempt to ascend the river; nor can it be gathered from his narrative that he believed it to penetrate far into the interior. VOYAGE OF HENDRICK HUDSON.