46 Reports and Proceedings — Geological Society of London. 



treatment of the Derbyshire " toadstones " rather leaves the ira- 

 ])ressioti that they would have beea described in connection witli 

 the Shropshire "diabases" but for tlie fact that "Mr. Arnohl 

 Bemrose regards them as contemporaneous lavas." That there 

 should be any difficulty in naming a rock befoi'e its mode of 

 occurrence, either as an intrusive mass or as a lava-flow, has been 

 determined, may present no terrors to the field-geologist ; but to the 

 Museum-Curator it is hardly less appalling than the idea that before 

 giving a rock a name it is necessary to determine its geological age. 

 The author, it is true, is faithful to the British School in rejecting 

 any distinction between rocks drawn from geological age ; but the 

 simplification in classification which should follow the removal of 

 this incubus is partly discounted in this, as in many other English 

 textbooks, by the fact that the hypabyssal groups are to a large 

 extent recruited from rocks which are so mildly intrusive as to be 

 included by Continental writers in their palgeovolcanic groups 

 (Ergussgesteine). 



The book has been brought up to date by references to recent 

 work, and still remains, what it was recognized to be on its first 

 appearance, one of the most trustworthy guides for the student who 

 wishes to take up the microscopic study of rocks. G. T. P. 



liEiPOiaTs .A.isriD i^s,ooei:e:xdiitc3-s. 



Geological Society op London. 

 I.— November 17, 1897.— Dr. Henry Hicks, F.R.S., President, 

 in the Chair. The following communications were read: — 



1. " The Geology of Eotuma." By J. Stanley Gardiner, Esq., 

 B.A. (Communicated by J. E. Marr, Esq., M.A., F.R.S.) 



The author describes the relationship of the island of Rotuma 

 (situated in lat. 12° 30' S., long. 177° 1' E.) to the adjoining isles. 

 It is almost separated into two parts, which are united by a narrow 

 neck of sand. The interior is composed of volcanoes, which have 

 emitted lavas and fragmental rocks. Around the volcanic rocks are 

 stratified deposits composed of sea-sand with volcanic fragments. 

 These are partly denuded, and are mantled round by coral-reef and 

 beach sand-flats. A remarkable cavern in the lava of Sol Mapii, 

 with lava-stalactites, is described; there is a similar cavern in 

 Au Huf Huf. 



An account of the prevalent meteorological conditions is also given. 



In an Appendix by Mr. H. Woods, M.A., some of the rocks are 

 described. They consist of olivine-dolerites and basalts and asso- 

 ciated fragmental rocks. 



2. " A Geological Survey of the Witwatersrand and other Districts 

 in the Southern Transvaal." By Frederick H. Hatch, Ph.D., F.G.S. 



After giving an account of the physical characters of the area, 

 the author proceeds to describe the various rocks referred to 



(1) The Karoo System, 



(2) The Cape System, 



(3) The Primary or Archaean System. 



