The astronomical expedition which the authorities at Harvard University have so long contemplated is now fairly started on its journey South. Primarily, the object of the expedition is to make a complete survey of the southern heavens to supplement the survey of the northem heavens which has been going on the last six years at Cambridge. As three-fourths of the survey has been accomplished here at Cambridge it will not be necessary for the expedition to remain in the South more than two years to finish it entirely.
Secondarily, the expedition, consisting of Prof. W. H. Pickering, A. L. Rotch, S. Bailey, E. S. King and Robert Biack, will observe the sun's total eclipse which takes place at 2 p. m. on January 1st, at a town called William, in the Sacremento Valley. Under favorable circumstances this eclipse will be visible over a strip of country one hundred and twenty miles long; it will also be visible as a sunset phenomenon in Canada near Lake Superior, and as a partial eclipse as far east as New York. Owing to the wide range of country from which the eclipse is visible an excellent chance is offered to solve various problems concerning the sun's course and the amount and intensity of the light emitted under the given conditions.
The expedition will take complete apparatus for the important work of photographing the spectrum of the sun and in addition will carry an ingenious instrument for measuring the brightness of the corona. One of the assistants started yesterday with a large part of the apparatus, for Peru; where a thorough study of the southern heavens will be made. While it is not yet assured that a permanent station will be established south of the equator, nevertheless the idea is seriously entertained and a part of the work of the expedition will be the examination of the exact facts in regard to climate and atmospheric clearness, facilities for work and transportation, communications, etc., to be found in Peru. The country is barren in the extreme and the fact that wood and water is scarce may interfere with the construction of a permanent observatory, but the rainless conditions are favorable as they give assurance that the interruptions of work from causes which are here so common will not occur, and as the station will be placed well up on the mountain side the observers will be above the line of fog, which is the most troublesome thing they will have to contend against.
The photometric observation of stars will be performed with the same instrument and according to the same method and standard as that by which that part of the heavens visible in Cambridge, from the pole to 30 degrees south of the equator has been already surveyed. Photographs will be made of the spectra of the southern stars and of the stars themselves directly. A complete map of the southern field will be made by combining a series of photographs taken in a systematic manner.
As it is very desirable that observations be taken on the Pacific coast to perfect the work done here in Cambridge, conferences have been held with the proprietor of the new observatory in Southern California looking to co-operation between that and the one in Peru. The permanency of the Peruvian station will depend largely upon the result of this conference.
A part of the apparatus which will be carried to Peru is a light portable frame building of one story with a ground area of three hundred square feet, which is to be the observatory of the party; the scarcity of wood and carpenters in Peru makes it prudent to build this here. The class of work which the expedition will undertake comes under the terms of the Boyden bequest. The cost of the work upon the Stella spectra is sustained by the Draper Memorial Fund.