476 Reviews — Calcite in Silicified Wood. 



ascended. About 100 feet higher in the Molteno Series is a dolerite 

 sill of the usual Karroo type, and the mineralization may possibly be 

 due to this phase of igneous activity. 



R. H. R. 



IX. A REMARKABLE OCCURRENCE OF CaLCITE IN SlLICIFIED WOOD. 



By Edgar T. Wherry. Proceedings of the United States 

 National Museum, vol. liii, pp. 227-30. 



IN 1915 Mrs. Charles D. Walcott collected in the Yellowstone 

 National Park a piece of silicified wood of Sequoia magnified 

 (ivnowlton), in which were numerous white grains with rhombic 

 crystal outlines and dark central inclusions. When thin sections of 

 the wood were examined the grains were found to consist of calcite, 

 occurring sometimes in simple crystals, but more frequently twinned, 

 often polysynthetically. The development of the crystals shows some 

 interesting features. In the centre there is generally an inclusion of 

 woody cells, distorted either very little or not at all, then comes 

 a layer of clear calcite with woody fibre which occasionally extends 

 along the boundaries of the twiu laniellse ; outside this, just within 

 the crystal, there is often a zone of disrupted cells, and finally 

 outside the boundaries of the faces, which are often curved, is a dark 

 compact band of tissue. The fibre round the crystals shows little or 

 no distortion, each cell being filled with a single quartz crystal; this 

 shows that the calcite must have been deposited before the quartz 

 and when the wood was so rotten that pressure was not transmitted 

 through it for any distance. 



The history of the specimen seems to have been as follows : — The 

 rotten wood was permeated by solutions containing calcium carbonate, 

 which at first deposited calcite quickly at certain places round the cells. 

 Then, later, deposition became slower and the cells were pushed 

 outwards by the growing crystals to form the dark band round the 

 edges. After a break in the deposition a final layer was deposited 

 so as to include some of the broken tissue on the edges of the crystals, 

 and finally the calcareous solutions gave place to siliceous solutions 

 which deposited quartz in the remainder of the tissues. 



W. H. WlLCOCKSON. 



X. — The Royal Society Club. 



IN the Annals of the Royal Society Club, the record of a London 

 dining -club in the eighteenth and nineteenth centuries (Macmillan, 

 pp. xv, 504, 1917, price 18s. net) Sir Archibald Geikie has published 

 a volume packed with biographical interest. Although such a book 

 can at best be but a record of fact, still there is a certain amount of 

 general interest within these covers. Prom various accounts one 

 gathers that almost from 1650 certain members of the future Royal 

 Society (1662) met together at taverns to discuss their interests, but 

 the earliest surviving document relating to the "Club" dates from 

 October, 1743. Since then the weekly dinner regularly continued 

 for sixty years, and the most curious portion of these records consists 

 in the bills of fare faithfully entered up week by week for more than 



