218 Notices of Memoirs — Additions to Fossil Botany, 1^70. 



order to determine this value, Mr. Hopkins tacitly assumed the 

 hypothesis which I rejected, and found the value of e on the sup- 

 position that it contained the same at every stage of the earth's 

 solidification. If, in accordance with my results, we make e equal 

 to or at least not less than e^, we would have P^:=P or P^zPu 

 values so entirely difi'erent from the observed value of precession 

 that I was led to conclude that the motion of rotation of the crust 

 and its contained fluid takes place nearly as if the mass were entirely 

 solid. Six years afterwards I reiterated the same result in the 

 Atlantis, and also showed from independent reasons why great 

 friction and pressure should be expected to exist between the fluid 

 nucleus and the inner surface of the crust. At the meeting of the 

 British Association, at Manchester, in 1861, I took an opportunity, 

 in the presence of Mr. Hopkins, of pointing out the inconclusiveness 

 of his results regarding the internal structure of the earth, and I 

 again distinctly repeated my former conclusions. Mr. Hopkins 

 promised a reply to my remarks, but this promise has never been 

 fulfilled." 



It appears from the number of Nature for March 23 that at the 

 meeting of the French Academy of Sciences, on the 13th of March, 

 M. Delaunay read a declaration, stating " that he acknowledged that 

 Mr. Hennessy had used the same arguments as himself against Mr. 

 Hopkins's theory relative to the fluidity of the interior parts of the 

 earth." 



11. — Keview and Synopsis of the Contributions to Fossil 

 Botany Published in Britain in 1870.^ 



By William Carruthers, F.L.S., F.G.S., of the British Museum. 



Carruthers, W. — On Fossil Cycadean Stems from the Secondary Rocks of 

 Britain. Trans. Linn. Soc, vol. xxvi. pp. 675-708, pi. liv-lxiii. 

 After investigating the nature of the Palseozoic remains referred to Cycadece, the 

 author describes twenty-five species belonging to eight genera. Four of the genera 

 are placed in one or other of the tribes of the existing Cycads, while two new 

 tribes are established for the remaining genera. 



On the Petrified Forest near Cairo. Geol. Mag. Vol. VII. 



pp. 306-310, PL XIV. 

 The so-called forest is described, and the different specimens of silicified woods 

 found in it are referred to two species of the genus Nicolia. 



On the Structure of a Fern-stem from the Lower Eocene of 



Heme Bay, and on its Allies, Recent and Fossil. Quart. Journ. Geol. Soc. 



vol. xxvi. pp. 349-353- 

 The stem ( Os?mmdites Dowkeri) is minutely described, aiid compared with that 

 of Osmunda regalis, L. A new arrangement of some described Fern-stems from 

 Palseozoic and Mesozoic rocks is proposed by the author. 

 Dawson, J. W. — On the Pre-carboniferous Floras of North-eastern America, 



with especial reference to that of the Erian (Devonian) Period. Abstract. 



"Proceedings of Royal Society," May 5, 1870. 

 The Erian Flora is revised, and twenty-three new species added. Large trunks 

 of Prototaxites were described, and also two species of Psilophyion, with details of 

 their form, structure, and fructification. The occurrence of Lepidophloios and 

 Calamodendron, noticed for the first time in the Middle Devonian ; specimens of 

 Cyclostigma and Cardiocarpum, and a new genus, Ormoxylon, were described. 



1 Reprinted from The Journal of Botany io^^ K-^riS., 1871. 



