138 Reports and Proceedings — Geological Society of London. 



Some critics will probably find fault with the comparatively brief 

 notices given of economic products. In a country of which the geology 

 is so little known nearly the whole book becomes of economic 

 importance. The geology of Cape Colony affords the key to the 

 rock structure of South Africa, and therefore to its mineral wealth. 

 Every engineer, miner, or prospector in South Africa, and those 

 being trained in this country for the colony, should therefore make 

 themselves fully acquainted with the main facts contained in this 

 book, and thoroughly master the many problems so ably and 

 clearly presented by Mr. Eogers. Walcot Gibson. 



s,:e]:f>o:rts -A-InTid i^s-ocssiDiisra-s. 



I. — Geologioal Society op London. 



February 1st, 1905.— J. E. Marr, Sc.D., F.E.S., President, in the 



Chair. 



Professor Garwood exhibited and commented on a set of twelve 

 lantern-slides illustrating the use of three-colour photography in 

 demonstrating the microscopic characters of rock-forming minerals 

 in polarized light. The slides were taken by the Sanger-Shepherd 

 process, in which yellow, green, and red screens were used. He 

 said that it was not a process that could be used very easily, but one 

 which required a good deal of time to produce really accurate prints. 

 Considerable difficulty was experienced in procuring objectives 

 which were truly corrected for the spectrum, the tendency in the 

 case of interference figures being to give different-sized rings for 

 different colours. The results did resemble very closely the 

 phenomena seen under the microscope ; and he had brought one 

 or two rock -sections shown on the screen, in case Fellows interested 

 in the subject would like to compare the slides with the original 

 sections. 



The following communication was read : — 



"On the Sporangium -like Organs of Glossopteris Broicniana,. 

 Brongn." By E. A. Newell Arber, M.A., F.L.S., F.G.S. 



It has been discovered that some specimens from New South 

 "Wales, on which numerous and well-preserved scale-fronds of 

 Glossopteris occur, also exhibit impressions of groups of minute 

 bodies, not unlike the sporangia of certain recent and extinct Ferns 

 and Cycads. The new organs are elliptical in shape, and measure 

 from 1-2 to 1-5 millimetres along the major axis. They are hollow, 

 sac-like structures, which open or dehisce longitudinally. Un- 

 fortunately no trustworthy evidence can be obtained as to their 

 contents. The fact that they have never been found, except in the 

 closest association with the scale-leaves of Glossopteris, is regarded 

 as an indication that they may be attributed to that genus; and 

 this conclusion is supported by the direct evidence of some of the 

 scale-fronds, which show scars of attachment and fragments of the 



