[ 120 ] 12 



past year, we have caused to be computed, at the expense of the institu- 

 tion, an ephemeris of Neplune, giving the position of the planet in the 

 heavens from August 4, 1846, to February 4, 1848, and also in the last 

 half years of 1848 and 1849. This ephemeris is based on the orbit of 

 Neptune established by Mr. Walker and corrected by the perturbations of 

 the planet Neptune by the action of Jupiter, Saturn, and Uranus, as de- 

 duced from the mathematical investigations of Professor Peirce, of Har- 

 vard University. 



We have distributed copies of this ephemeris to all persons known to 

 us who are interested in practical astronomy, not only in this country but 

 in Europe. It has been received with high commendation, and is found 

 to give the actual phice of the planet in the heavens within the limits of a 

 few tenths of a second of arc; indeed, the coincidence of the calculated 

 and observed places 18*^^80 marked, tliat, were the actual planet of the 

 heavens and that of the ephemeris to be considered as a double star, they 

 would have so close a proximity that no telescope yet constructed could 

 separate them. 



Occultations for 1850. 



A set of tables in continuation of those mentioned in the last and 

 preceding report for facilitating the calculation of the appearance of oc- 

 cultations of fixed stars by the m.oon during the year 1850 has been prepared 

 by Mr. Dovvnes, of Philadelphia, and published by the institution. At 

 the last session of Congress an appropriation was made for establishing a 

 Nautical Almanac, which will furnish, among other aids to astronomical 

 observation, sets of tables of the kind just mentioned. Lieut. Davis, of 

 the United States navy, to whom the superintendence of this national 

 work has been intrusted, recommended that the expense of tlie preparation 

 of the tables for 1850 should be defrayed from the appropriation for the 

 almanac; and this recommendation has been concurred in by the Secretary 

 of the Navy. The institution has, therefore, been called upon merely to 

 pay for the printing and distribution of the tables, and thus again en- 

 abled, with a small outlay of its funds, to afford important facilities for 

 tlie advance of science. 



Meteorology. 



Under the general head of researches we may also give an account of 

 the progress made in establishing the system of meteorological observa- 

 tions proposed in the preceding reports. Circulars describing the plan of 

 opeiation were distributed to the several parts of the Union through mem- 

 bers of Congress at the last session, and the results fully equalled our 

 anticipations. From localities widely separated from each other, and dis- 

 tributed over the greater portion of the Unite'! States, about one hundred 

 and fifty monthly returns are now regularly received. To carry on this 

 system efficiently, much labor is necessarily required in the way of cor- 

 respondence; but it bids fair to furnish the institution with a wide field 

 of usefulness in bringing it into communication with individuals v/ho, 

 though secluded in position, arc desirous of improving themselv^cs, as 

 well as of promoting general knowledge. The correspondence we have 



