ON MAPPING THE SURFACE OF THE MOON. 307 



and have been obliged to content myself with small contributions ; but I 

 abandon not the hope that I shall yet be enabled to make observations with 

 great instruments. 



Respecting the rills, I have now ready for printing a small pamphlet, in 

 which are classified, up to February 1865, all those known to me. I hope 

 to get it published in Leipzig. It contains 425, and these are divided in the 

 following order : — 



From 1787 to 1801 Schrbter discovered 11 rills. 

 „ 1823 „ 1827 Lohrmann „ 75 „ 



„ 1832 „ 1841 Madler „ 55 „ 



„ 1847 „ 1848 Kinau „ 6 „ 



„ 1842 „ 1865 Schmidt „ 278 „ 



Since that time I have discovered thirty or forty new rills. I point out as 

 particularly remarkable the systems I observed in 1849-1862 near Rams- 

 den and Aristarchus. The rills near the southern capes of the Apennines, 

 Hyginus, Ariadseus, and Sabine, are in connexion with that of Goclenius, as 

 rills are existing in the plain near Torricelli; I enclose only a few slight 

 sketches of remarkable rills, which, in case they should not yet be known to 

 English astronomers, may give occasion to future researches. Those who are 

 in possession of large telescopes should not neglect to make drawings of 

 craters of the most minute kind, which are visible even in very small and 

 well-limited regions, as the craters in Plato, Archimedes, Hevelius, Gassendi, 

 Mersenius, Marius, ike. 



Less important appears to me the study of such disturbed formations as 

 Maginus and Longomontanus, because here we may never arrive at certain 

 conclusions, for all the territory appears to consist only of craters of the 

 smallest kind. As other objects of a rigorous and searching examination, 

 I mention those little craters, crater-rows, crater-rills, that, situated in the 

 interior of the ring mountains, form the limits of the plain and the be- 

 ginning of the wall mountain. Here the eruptive forms have issued, as it 

 were, out of cracks, and in parts of considerable and high mountains, where 

 two mountain-masses, approaching each other, form a narrow valley, or a sharp 

 corner. Just as important is the parallelism of many little craters, where 

 they, as on Etna, cover .the exterior of the walls of the mountains. Among 

 such forms, spoken of to the fullest extent of the word, I class such bodies as 

 Copernicus, with his many hundred neighbouring craters. But in a more 

 limited sense, however, I comprehend examples, such as the craters outside 

 of the north wall of Newton, where the wall mountains, covered with 

 craters, slope against the south-east wall of Moretus. But everywhere a 

 keen and unprejudiced course of observation will indicate that rills are only 

 crater-rows in a particular modification, as the innumerable transformation - 

 forms prove, and as Madler first pointed out. 



In the climate of Hellas (still more so in that of the more southern isles), 

 so favourable for astronomical observations of every kind, many of the most 

 important problems would in a short time be solved, if a practised . observer, 

 completely free from hypothetical views, were furnished with the necessary 

 means. e 



Athens, October 6th, 1865. 



In illustration of this memoir, Herr Schmidt has forwarded a drawing 

 (Plate IX.) of the rills west of the Mare Serenitatis, from Posidonius to a 

 point south of Littrow. 



t2 



