4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 3, 



beds at Zwickau, which M. Gutbier has distinguished by the name 

 of ' graues conglomerat/ are nothing more than the base of the 

 Roth-hegende of Germany," 



In a second letter to Sir Roderick Murchison, dated November 25, 

 1848, Professor Naumann says, "In reply to your letter of the 20th 

 I hasten to inform you that I agree entirely with your idea, that the 

 Roth-liegende and the Zechstein together constitute but one and the 

 same formation, although in Germany these two members are very 

 often distinctly separated from each other. It is for this reason that 

 I shall always preserve this distinction in any description of the Per- 

 mian system, such as it presents itself in our country. In reference 

 to my assertion, that the coal-beds of Oschatz are separated from the 

 Roth-liegende by porphyry, the term Roth-liegende was there used 

 in a purely petrographical sense, as signifying a sandstone coloured 

 red, and to indicate that the beds whose characters truly represent 

 what may be called Roth-liegende commence in this section above the 

 porphyry only. At all events, these red beds are only part of the 

 same whole which includes the grey beds below the porphyry, the 

 latter rock being intercalated in the middle of the Permian sandstone. 

 This takes place both near Oschatz and Rohrlitz, though the pheno- 

 menon is more clearly seen near the last-mentioned town, as is exhi- 

 bited in the 14th sheet (Grimma) of our geological map. Political 

 troubles have interfered with the working researches near Oschatz, 

 but tranquillity being restored, they will be renewed in the spring. 

 In the mean time, M. Gutbier will give a description of the Permian 

 flora of Saxony, the Saxon fauna of the same system having been 

 already published by M. Geinitz." 

 December 26, 1848. 



2. On Change of Climate resulting from a Change i?i the Earth's 

 Axis of Rotation. By Sir John Lubbock, Bart., F.R.S. 



[Communicated in a letter to Charles Lyell, Esq., V.P.G.S.] 



I HAVE thought a good deal upon phaenomena indicative of a change 

 in the climate of places on the earth's surface and of changes in the 

 relative position of land and water, and as this is a subject to which 

 you have devoted so much attention, I wish to know whether you 

 think the following speculations of any value, or whether you think 

 they have already been anticipated by any mathematician. 



It follows from the theory of rotation of a solid body, as is well 

 known, that, 1 . If a body revolves about certain axes which are called 

 principal, and no extraneous force acts upon the body, it will con- 

 tinue to do so for ever. 



So in the case of the earth : if EQ is the equator 

 and P the pole, if the earth, as is supposed, re- 

 volves at present about CP the axis of figure, as 

 this is a principal axis, it will continue to do so for 

 ever, and has done so since the origin. Hence the 

 geographical latitude of any place on the earth's 



