ASTRONOMY. 53 



mitted, and numerous sketches made in view of constructing a map 

 of her surface. So far a preliminary outlined map has been plotted 

 out on a scale of 150 centimeters to the diameter. A duplicate 

 sketch of this preliminary map has been made on 121 sections, these 

 being intended as the working sketches, and are afterwards trans- 

 ferred to the large map. Several years will be necessary to com- 

 plete this work. 



During the year a paper on the " Transit of Mercury " has been 

 published in the American Journal of Arts and Sciences, and a report 

 on the total eclipse of the sun has been sent to the Naval Observa- 

 tory for publication ; besides, a paper on the " Observations of Dei- 

 mos " has been sent to the Astronomische Nachrichten, also for publi- 

 cation. A great deal of material is on hand awaiting publication ; 

 but, as the expense would be too large for the limited means of a 

 private individual, it will necessarily remain unpublished until ade- 

 quate means are found. 



During the coming year the physical observations of the sun and 

 planets will be continued. The aim will be especially to study the 

 j)lanets Mercury and Venus, about which so little is known. Mars 

 will also be studied in view of completing the map of its surface. 

 It will be endeavored to draw as many nebulae as possible to enlarge 

 the collection of similar drawings already obtained. A series of ob- 

 servations on variable stars is about to be undertaken by my assist- 

 ant, Geo. H. Trouvelot. 



Chicago, 111. : Dearborn Observatory. 



Professor E. Colbert, Director. 



1st. Personnel. Superintendent, Elias Colbert, M. A. ; Assistant, 

 George P. Barton. S. W. Burnham, Esq., is using the Equatorial 

 Telescope, but has no official position in the observatory. 



2d. Instruments. I enclose printed statement from the catalogue 

 of the University of Chicago, with which the Dearborn Observatory 

 is connected : 



" The Dearborn Observatory forms the Astronomical Department 

 of the university. Its objects are to make original researches in as- 

 tronomical science, to assist in the application of astronomy to ge- 

 ography, in communicating exact time, and other useful objects, and 

 to furnish instruction in astronomy to the students of the university, 

 both those in the regular course and those who wish to give especial 

 attention to the study. 



" The principal instruments of the observatory are : 



" (1.) The great Equatorial Refracting Telescope, made by Alvan 

 Clark & Sons, of Cambridge, Mass., in 1861, and mounted in the 

 Dearborn Tower, which was built by the munificence of the Hon. J. 

 Young Scammon, LL.D. This instrument was the largest refractor 



