Geological Society of London. 335 



and acervulina. He stated that fragments of Eozoon, included in 

 dolomitic limestones, have their canals filled with ti'ansparent dolo- 

 mite, and sometimes in part with calcite. In one specimen a por- 

 tion was entirely replaced hy serpentine. The author called parti- 

 cular attention to the occurrence of serpentinous casts of chamberlets, 

 single or arranged in groups, which resemble in form those of the 

 Globigerine Foraminifera. These may belong either to separate 

 organisms, or to the Acervuline layer of the Eozoon ; the author 

 proposes to call them Archceosplierince, and describes them as having 

 the form and mode of aggregation of Globigerina, with the proper 

 wall of Eozoon. The author discussed the extant theories as to the 

 natui*e of Eozoon, and maintained that only that of the infiltration 

 of the cavities of Forarniniferal structure with serpentine is admis- 

 sible. He particularly referred to the resemblance of weathered 

 masses of Eozoon to Stromatoporoid Corals. 



2. " Kemarks upon Mr. Mallet's Theory of Volcanic Energy." 

 By the Eev. 0. Fisher, M.A., F.G.S. 



Mr. Mallet's paper, read before the Eoyal Society in 1872, was 

 discussed by the author seriatim as far as it seemed open to criti- 

 cism. With respect to the condition of the earth's interior, whether 

 it be rigid or not, Sir W. Thomson's arguments for rigidity were 

 referred to, and geological difficulties in accepting his conclusions 

 suggested. Mr. Mallet's views regarding the formation of oceanic 

 and continental areas, that they have on the whole occupied nearly 

 the same positions on the globe at all periods from the very first, 

 were excepted to on the ground that all continental areas with 

 which we are acquainted are formed of water-deposited rocks, and 

 that therefore those areas must at some time have been sea- 

 bottoms ; and if these wide features have not occupied the same 

 positions which they now do from the very first, Mr. Mallet's ex- 

 planation fails, that they were caused by unequal contraction when 

 the crust was first permanently formed and thin. It was also 

 shown that the theory of unequal radial contraction cannot account 

 for the difference of elevation between continental and oceanic 

 areas upon reasonable assumptions. For if we consider the crust to 

 have been 400 miles thick (which cannot be considered thin), and to 

 have cooled from 4000° F. to zero (a most extravagant supposition), 

 then, if the crust had contracted one-tenth more beneath the 

 oceanic area than it had done beneath the continental, we should 

 only get a depression of one mile for the oceanic area, using Mr. 

 Mallet's mean coefficient of contraction. 



The main feature of Mr. Mallet's theory was then discussed, viz. 

 that "the heat, from which terrestrial volcanic energy is at present 

 derived, is produced locally within the solid shell of our globe, by 

 transformation of the mechanical work of compression or crushing 

 of portions of that shell, which compressions and crushi'ngs are 

 themselves produced by the more rapid contraction by cooling of 

 the hotter material of the nucleus beneath that shell, and the con- 

 sequent more or less free descent of the shell by gravitation, the 

 vertical work of which is resolved into tangential pressures and 



