"Vol. 65.] PROCEEDINGS OF THE GEOLOGICAL SOCIETY. CXxix 



Dr. G. F. Herbert Smith, M.A., F.G.S., exhibited two forms of 

 refractometer. The one (which reads directly to the second, and by- 

 estimation to the third, place of decimals) has a range extending 

 from 1*300 to 1*795, and is intended for all translucent substances, 

 especially minerals. The other (which reads directly to the third, 

 and by estimation to the fourth, place of decimals) has a range 

 extending from 1*3200 to 1*4200, and is intended for use with 

 water and solutions in water, especially brines, for which reason it 

 may be called a salinometer. The liquid film is illuminated from 

 above, and the optical arrangements are such that the critical edge 

 is blue, if coloured at all, in white light. Since the refractive 

 indices of liquids change rapidly with the temperature, a water- 

 jacket is provided for controlling the temperature of the observa- 

 tion ; a thermometer, reading to degrees centigrade, is attached, 

 underneath the instrument. The glass prisms are removable for 

 cleaning purposes. 



In addition to the exhibit just described, the following specimens, 

 maps, etc. were exhibited : — 



Specimens of Carboniferous Limestone from County Clare, thin 

 sections of corals, and lantern-slides, exhibited by J. A. Douglas, 

 M.A., B.Sc, F.G.S., in illustration of his paper. 



Five sheets of the 6-inch Geological Survey Map of Scotland, 

 presented by the Director of H.M. Geological Survey. 



Map of the Coalfields of the United States, by M. R. Campbell, 

 1908, presented by the Director of the U.S. Geological Survey. 



