100 THE HAMILTON ASSOCIATION. 
sketch as to illumination and other particulars to be kept in mind. The 
drawing, with its craters, mountains, rills, with all details of the part 
of the lunar sitrface adjacent, were next modelled in clay, and from 
the clay models, after they were dried and corrected by further tel- 
escopic observation, plaster casts were taken. These casts were then 
carefully illuminated to throw shadows similar to those projected by 
the objects when the drawing was made, and finally they were photo- 
graphed. By such an unexampled expenditure of time and _ skill, 
were obtained those contrasts of light and shade, and delicate half 
tints, which make the Nasmyth lunar drawings so exquisitely beautiful. 
To the instructive writings on lunar subjects by Webb, Elger 
and other popular writers, it is needless to refer. Nor need mention 
be made of the writings and eloquent addresses on these subjects by 
the late Prof. Proctor. His works speaks best for themselves to all 
who care for astronomical instruction. 
The most complete treatise accessible to English readers con- 
cerning the moon is that published a few years since for Mr. E. 
Neison, F. R. A. S. Professedly based on the great work of Beer 
and Meedler, it has original merit, and not only includes his own 
observations for eight years, but those of Mr. Webb and other obser- 
vers who aided him in his work, and also contains much interesting 
matter from the works of Schrceter and of Lohrman. His instru- 
ments were of the best class, and included a fine 6 in. refractor, and 
a 9% in, With-Browning silvered glass reflector. The lunar map 
accompanying his book is in twenty-two sections, and is on a scale 
of two feet to the moon’s diameter. Though his chart is more than 
a third smaller than that of Beer and Meedler, it is finely engraved, 
shewing more formations than are given in their map, and more rills 
than are shewn by Schmidt in his ‘“‘ ~z//en an dem Mond.” 
Neison groups the lunar surface under the names of plains, 
craters and mountains. His plains include all the large, dark, com- 
paratively smooth tracts, called by the early selenographers dZazza ; 
the smaller tracts they named Fadus, Lacus, or Sinus, and the 
brighter, smooth tracks which previously had received no name. 
For easy reference he divided the lunar craters into walled-plains, 
mountain-rings, ring-plains, crater-plains, craters, craterlets, crater- 
pits, crater-cones and depressions. His special names for the lunar 
mountains are great ranges, highlands, mountain-peaks, peaks, hill- 
