306 report — 1865. 



partly at Hohenfeld, near Hamburg, and partly with the instruments of the 

 observatory in that town. In the year 1845 I observed the moon but seldom, 

 at the observatory at Bilk, near Dusseldorf. From 1846 to 1853 I have 

 obtained at Bonn, and from 1853 to 1858 at Olmutz, many sketches ; and with 

 the refractor of the observatory at Olmutz I made and reduced 4000 micro- 

 metrical measures of the altitudes of the mountains of the moon. In the 

 interim I was twice so fortunate as to be able to apply refractors of the first 

 class to the moon, by the kindness of Encke and Bruhns in Berlin (1849), 

 and by the favour of Secchi in Rome (1855). Since 1860 I have con- 

 tinued these labours at Athens, partly because the very defective condition 

 of this observatory is such that I could not participate in greater researches, 

 or in those which appear more important at the present day. Perceiving, in 

 January 1865, that I coidd not with satisfaction continue to neglect the mass 

 of accumulated material, I considered it necessaiy to unite all my sketches 

 in one great picture or plan ; and I resolved at once to undertake that labo- 

 rious work, without contemplating any publication. I selected a scale double 

 that of the charts of Lohrmann and Madler, giving my general chart, consist- 

 ing of four folios, a radius of 3 feet, or about '2 metres diameter. This is now, 

 with the assistance of my original sketches (nearly 1000), so far accomplished 

 that the positions of the principal objects are laid down ; and even in the 

 landscapes near the limb but little is wanting. The chart exhibits already 

 a considerable progression, and will probably be completed in two or three 

 years. I chose the method of those authors, and took for points of the first 

 and second order the data of Madler and Lohrmann. ' The whole detail is 

 based upon my own observations only. 



The edition of Lohrmann's works was transferred to me from the pub- 

 lishers in Leipzig iu the year 1854. The copper plates of all the twenty-five 

 sections, with the exception of part of the shading, are completed, and I 

 possess already a perfect copy. In the text to this chart I shall give a 

 critical comparison with Madler. Both in their way form well-executed 

 charts for the selenographical local determinations, the proper and true basis 

 of the more modern selenography of which Tobias Mayer laid the first foun- 

 dation. Let us continue in trying, by the aid of more powerful telescopes, 

 to represent the topography of the yet undelineated details of the surface of 

 the moon, without, however (so far from setting a determinate limit), being 

 able to see the end of such a work ; it is as if from the ordinary determina- 

 tions of place of the brighter stars down to the eighth magnitude one passed 

 on to that of the stars in the Milky Way. 



The study of the rills has particularly occupied me during the last fifteen 

 years. The resemblance of numerous transformations and combinations of 

 the rills and craters, has led me to the opinion that all rills present only 

 volcanic phenomena, like all the rest of the moon. The study of the topo- 

 graphy of our satellite will at onee become very important for our geology. 

 But it is a great error to believe that a survey once or twice of a mountain 

 of the moon would entitle us to make certain comparisons or to arrive at 

 certain conclusions. I find, after many years' minute observations, that at 

 present it is prudent to avoid all speculations, and at first and before all 

 things to establish an extended topography in conformity with our present 

 means, free from contracted views, and so far exact and searching that we 

 may hope thereby to give satisfaction to a remote posterity. That was 

 also the opinion of Alexander von Humboldt, with whom I had often, from 

 1853 to 1856, communications on the subject. I myself have never been in 

 possession of sufficient means to produce anything important for selenography, 



