i88i-i882.] ^ 121 



banks of the Lower Bann. Remarks were made on their 

 collection and preparation for the microscope, and it was stated 

 that our owm country is favourable for their growth, numerous 

 interesting species having been found. 



At the conclusion of the paper, several members exhibited 

 slides of diatoms under microscopes. Photographs and draw- 

 ings were also exhibited, and some plates from Schmidt's *' Atlas 

 of the Diatomaceae." The examination of these and the ani- 

 mated conversation on the various points touched upon by the 

 reader concluded a very instructive evening. 



The fourth meeting for the session was held in the Museum, 

 on Tuesday evening, February 21st — the President, Robert 

 Young, Esq., C E., in the chair — when two communications 

 were brought forward. 



The first was by Mr. Swanston, on "Recent Discoveries in 

 the Lower Palaeozoic Rocks." After referring to the great 

 advance made in scientific research during the past year, and 

 especially referring to that of geology, the reader went on to 

 give a brief review of the history of research in the lower 

 Palaeozoic rocks, as defined by Murchison, Sedgwick, and others. 

 A large tabulated sheet on the wail showed at a glance the 

 opinions of the various leaders in the matter of the division of 

 these ancient beds into groups. He then proceeded more fully 

 to review what had recently been done in rocks of pre-Camb- 

 rian age, describing in order four great groups— the Pebidian, 

 Dimetian, Arvonian, and Lewisian — into which they had been 

 divided by Dr. Hicks. It was stated that one of the results of 

 researches in these ancient strata had been to class among the 

 sedimentary rocks extensive areas in Wales, &c., which had 

 previously been considered igneous. The difficulty in correla- 

 ting widely separated areas of these rocks was then referred to, 

 the beds being highly metamorphosed and entirely devoid of 

 organic remains. Under such conditions mineralogical charac- 

 ter is mainly relied upon as a guide. The microscope also 



