RESEARCH COMMITTEES. 537 



and subdivision, to which geologists have not yet attained, 

 and to which they are not hkely ever to attain. For instance, 

 one geologist may regard the Desert sandstone of northern 

 and western Queensland as Tertiary, another as Upper Cre- 

 taceous, and a third as Permian. The mapping of all three 

 may have its value, but it would be absurd to insist before 

 recognising it that all three should agree on the colour and 

 symbol by which the deposit is to be represented. 



' ' In selecting the colours to be employed on any given geo- 

 logical map, I would say the general conditions are : first, a 

 sufficient contrast ; second, something in common to all the 

 subdivisions of each formation or system ; and, third, a pleas- 

 ing and harmonious general effect. It is of the highest im- 

 portance, in view of the fading of all colours with age, that 

 each map should be accompanied by an index, in which the 

 various colours used are repeated and explained ; and that a 

 symbol should be written or printed on every coloured area in 

 the body of the map, as well as on the corresponding tablet in 

 the index. 



"In selecting colours, due consideration should be given to 

 the style of topography of the map. Thus the fine distinctions 

 between the shades of black which might be employed under 

 a ' unification ' system for subdivisions of the Carboniferous 

 rocks would be lost on a map already black with hill-shading. 

 Eut most of all the method of reproduction of the colours 

 would have to be taken into account. It may sometimes be 

 convenient to use water-colours ; at other times, simple black 

 and wdiite may suffice, wdien cross-hatching, stippling, and other 

 devices may be resorted to with advantage. Different combina- 

 tions and modifications of colour will be possible and advisable 

 according as lithography, photo -lithograph}', zincography, 

 photo -zincography, or chromo- lithography is employed as 

 the means of reproduction. The main thing is that the index 

 should correspond, both in colour and symbol, with the body 

 of the map, and that it should be self-explanatory. 



" In anticipation of an answer to the above objections, I may 

 add a few words of a personal bearing. I do not point to my 

 own maps as examples of my beazc ideal of geological mapping. 

 It so happens that the office of the Geological Survey of Queens- 

 land is in the northern part of the colony, while the reports of 

 the department, and maps accompanying the reports, have to 

 be sent to the capital to be printed. Owing to the haste with 

 which the reproduction of reports and maps has generally to 

 be carried out, the distance between Brisbane and Townsville, 

 and the fact that when proofs are ready I am frequently absent 

 from head-quarters, the proofs are rarely revised by me. Hence 

 it is no uncommon thing for colours to be employed the use of 

 which I never contemplated. Even wheii this happens, how- 



