22 S. Mis. 53. 



of Cambridge, an ephcmeris of Neptune had been deduced, which has 

 been accepted by all the astronomers of the world, as the only certain 

 guide to the position of the planet. This ephemeris was prepared for 

 1848 and 1849, at the expense of the Institution ; but since the last 

 mentioned date it has been calculated at the expense of the appropria- 

 tion for the Nautical Almanac, while the cost of printing and distribu- 

 tion has been defrayed by the Institution. The same arrangement will 

 continue for the ephemeris of 18-53 and 1854, after which the whole 

 will be turned over to the Nautical Almanac. 



Occultations. — The moon in her passage eastward around the earth 

 continually passes between us and the fixed stars or planets which lie 

 in her path, and obscures them from our view. The instant of the 

 disappearance of a star behind the moon7 or the occultation of a star, 

 as the phenomenon is called, can be noted by observers widely separ- 

 ated from each other, and hence this phenomenon becomes a ready 

 means of determining the difference of longitude between two places. 

 The employment of occultations for fixing geographical positions is 

 easy, and leads to accuracy in the results. The telescope may be 

 of moderate size, and requires no accurate adjustment; the position 

 assigned it may be such as to suit the convenience of the observer. 

 The frequent occurrence of occultations renders the use of them of 

 great importance to the travelling observer, and the pubhcation of lists 

 of these, and of tables for their reduction, is essential to the improvement 

 of geography. They are of particular value in this countr}'' on account 

 of the frequent exploring and surveying expeditions now carried on by 

 our government and our people, and to be continued for an indefinite 

 time in the extensive territory of the West and the newly acquired pos- 

 sessions of the Southwest. Tables of occultations were prepared and 

 pubhshed at the expense of this Institution for 1849 and 1850, but for 

 subsequent years the expense of their preparation has been defrayed 

 by the appropriation for the Nautical Almanac, under the direction of 

 Lieut. Davis, while the composition and press- work is still at the ex- 

 pense of the Institution. As soon as the Nautical Almanac is fully 

 commenced, the publication of these tables will be entirely relinquished 

 to this enterprise of the government. 



Up to 1850 the tables published were of occultations visible in the 

 United States. Since, however, the preparation of the tables has been 

 in charge of the director of the Nautical Almanac, the list has been so 

 extended as to make it useful to geographers in general as well as to 

 those of the United States. This extension was rendered important on 

 account of the surveys undertaken by our government in other parts 

 of the globe. Also, a table has been added, giving the correction of 

 the latitude due to the oblate spheroidal figure of the earth. 



When we consider the character and condition of the vast continent 

 of North America, which it belongs to us chiefly to reduce to a habit- 

 able and civilized state, we shall perceive that the practical scientific 

 explorer has no higher duty than to settle the geography, the magnet- 

 ism, the natural history, and the climate of these regions. 



Researches. — At the session of the Regents in 1849, an appropriation 

 was made to supply Lieutenant Gilliss with a telescope for his expe- 

 dition to Chili, to aid him in his observation^ for a new determination 



