48 Correspondence — Mr. A. StraJian — Prof. T. G. Bonney. 



COAL UXDEE NEW EED SANDSTONE. 



Sir, — Allow me to express my regret that I should have over- 

 looked the paper read by Mr. De Eance before the Geological Society 

 of Manchester, in which he gives a detailed section of the Winwick 

 Borehole, one of those which I described in my paper on Coal under 

 Kew Red Sandstone, and identifies the limestone met with in this 

 borehole as the probable equivalent of the Ardwick Limestone. 



I was first made aware of this paper by Mr. De Ranee's letter in 

 your last Number. A. Strahan. 



Chestee, 24iA November, 1881. 



COLOUEING OF GEOLOGICAL MAPS. 

 Sir, — I should be glad if some member of the English Committee 

 for reporting upon the colours, etc., to be employed on geological 

 maps, would kindly explain to me one or two difficulties which the 

 following passage in their report (see pp. 560-61, of this Magazine 

 for December, 1881) has caused me : — "Igneous Rocks. — Four colours 

 would suffice. ... 



Basalt and Greenstone Dark Carmine. 



Trachyte, Felstone, etc Permanent Scarlet. 



Granite Vermilion. 



Modern Volcanic Eock Light Orange." 



I believe there are three coarse crystalline rocks called syenite, 

 diorite, and gabbro, which can often be recognized by the eye with 

 tolerable certainty. How are they to be coloured ? Do any of these 

 alleviate the loneliness of granite, or ai'e the arms of greenstone wide 

 enough to embrace them all ? Again, we are told that modern 

 volcanic rocks are to be coloured " light orange." But I thought 

 basalt and trachyte (for which separate colours are provided) were 

 frequent products of modern volcanos ? Further, many authors in 

 rough grouping put the leucite-basalts and the nepheline-basalts 

 with the ordinary or felspar-basalt ; if so, what are the modern 

 volcanic rocks ? if not, on what grounds are felspar-basalt and 

 trachyte considered so much more ancient than the others ? The 

 olivine rocks and serpentine are, I suppose, omitted on the ground 

 De minimis non curat lex. 



I should be really thankful to have my pei'plexities enlightened ; 

 for I feel quite hopeless of solving them without external help ; and 

 if any member of my class asked me for an explanation I should not 

 know what to say, unless I modified a well-known formula for 

 silencing doubters, and replied : Bononia locuta est, causa fiuita est. 

 T. G. Bonney. 



Norwich Geological Society. — At the Annual Meeting of this 

 Society, held at the Royal Hotel, Norwich, on November 8, 1881, 

 Mr. W. Whitaker, B.A., F.G.S., was elected President in the room 

 of Mr. J. H. Blake. The retiring President gave an elaborate 

 address on Conservancy of Rivers, Prevention of Floods, Drainage, 

 and Water Supply. Mr. Whitaker, who is engaged on the Geological 

 Survey of the neighbourhood of Lynn, announced at the ensuing 

 meeting, held on December 6, his discovery of Totternhoe Stone 

 near Roy don Church, not far from Grimstou Road Station, on the 

 Lynn and Fakenham Railway. 



