The advance made in astronomical science during the 50 years past is among the wonderful facts comprised in the record of the 19th century, and it is true that since it became fairly organized and equipped, Harvard College Observatory has been in the front rank in the march. A review of this progress so far as pertaining to the institution at Cambridge, is, therefore, timely. A history of 50 years, embodying so many facts of the first importance and interest as does this, cannot, even with the most resolute purpose as respects brevity, be disposed of in a single chapter. This, accordingly, will be the first of a series. The reader may be assured at the outset that the topics to be touched upon are various and in themselves attractive, and that, so far as possible, technicalities will be shunned. Regarding the period of beginning just referred to as the blossoming, whence has followed abundant fruitage, it may be remarked that a long time passed between the budding and the blossoming, and that indications of the flow of a vital current are recognizable at as remote a date as 1761. In that year the sloop owned by the province of Massachusetts was fitted out at public cost to convey Prof. John Winthrop and others connected with the college, provided with instruments belonging to the college, to Newfoundland, for observation of a transit of Venus. In 1780, notwithstanding the financial straits incident to the war, the commonwealth provided a small vessel of war, called a “galley,” to take Prof. Samuel Williams, of the college, and party to Penobscot to observe a total eclipse of the sun. The first definite record pointing to a college observatory is of date 1805, when John Lowell, the uncle of that John Lowell who founded the Lowell Institute, being in Paris, consulted with Delambre, an astronomer of note, and procured from him written instructions as to suitable buildings and instruments for an observatory. This document was sent to the college authorities at Cambridge. No official action followed. The next of record is that the college authorities in 1815 appointed a committee to consider and report upon an eligible plan for an observatory. This is supposed to have been the first corporate action taken in the United States, having such an object in view. The doings of this committee are notable in two particulars, at least. They brought into official relations with the college for the first time, the man who was destined to be the builder and organizer of the observatory, 25 years later, William Cranch Bond.