As in a collection of graphical illustrations of the surface and of the inner structure of the earth's crust, general maps precede those of a special character, it has seemed to me that in a physical description of the Universe it would be most appropriate, and most in accordance with the plan of the present work, if, to the consideration of the entire Universe from general and higher points of view, I were to append in the latter volumes those special results of observation upon which the present condition of our knowledge is more partie ularly based. These volumes of my work must, therefore, in accordance with a remark. Already made (cosmos, vol. Iii., p. 5 be considered merely as an expansion and more careful exposition of the General Picture of Nature (cosmos.