560 Notices of Memoirs — On the Geological Congress. 



ancient University of Bologna, and President of the Congress ; and 

 ]\I. F. Giardano, chief Mining Engineer and head of the Geological 

 Survey of Italy. 



International Gkologioal Congress. 

 Final Eecommendations of the English Committee for re- 

 porting UPON the Colours, Signs, etc., employed on 

 Geological Maps. (Presented to the International Geological 

 Congress at Bologna, September 26, 1881).^ 



1. For general maps of large areas, and for small-scale maps of 

 individual countries, it is desirable to frame some scale of colours 

 which can be readily used and easily understood by all nations. 



2. For sedimentary rocks a scale of colours, based on the order of 

 colours of the solar spectrum, is desirable for such small or general 

 maps ; subject to such modification as may appear necessary. 



3. The scale of Colours recommended is : 



Pleistocene Burnt Sienna. 



Pliocene Buff. 



Miocene Orange. 



Eocene Pure Yellow. 



Cretaceous Green. 



Jurassic Blue. 



(Lias Indigo.) 



Trias Venetian Red. 



Permian Chalons Brown. 



Carboniferous ... Dark Grey, distinguishing limestone by a wash of blue. 



Devonian Indian Eed. 



Silurian Violet. 



Cambrian Purplish Violet. 



Pre -Cambrian ... Purplish Carmine. 



4. Sub-divisions of Formations. — Three or four shades of the body- 

 colour to be used ; the darkest shade for the lowest or oldest sub- 

 division. Dots, lines and white spaces to be used where necessary. 

 Where lines or dots are used, they should, if possible, be the same 

 as the body-colour but a darker shade. It was suggested that if 

 possible such lines should run from N.W. to S.E. of the map. 



4a. Freshwater formations should be distinguished by some method. 

 Coloured lines or engraved signs were suggested. 



5. Metamorphic rocks to be marked, as such, by dark bands of 

 colour, the same as denoting the age, but a darker shade. When the 

 age of the metaraorphism is known, the fact may be denoted b}'^ ad- 

 ditional bands of colour of the age of the metamorphism. Thus : 

 Cambrian rocks altered in Cretaceous times would be purjilish-violet, 

 striped with alternate lines of dark purplish-violet and green. 



1 The resolutions passed by the Congress at Bologna differ from those adopted by 

 the English Committee chiefly in the following particulars : — 



3. The scale of colours for the Map of Europe is modified as stated above. The 

 colours for Palaeozoic rocks being left undecided for the present. 



4« and 6 were not considered. 5 only so far as to define the colours to be used for 

 crystalline schists of Pre- Cambrian or of unknown age. 



