792 Museum of Economic Geology. [No. 118. 



red, yellow, and green colours from that of the chromate of iron with 

 oxides of other metals. For the illustration of the department of 

 mineral pigments, specimens, therefore, of the various simple pigments, 

 founcl in nature, and the compound ones formed by art, ought to be 

 procured. When attention has been attracted to this branch of the 

 subject, we may anticipate the development of information relative 

 to native colouring- materials and modes of applying them, that could 

 not fail to prove both interesting and useful. With the department 

 under notice, I have associated that of mineral dyes, because many 

 minerals included in the one, belong also to the other. A similar 

 series of illustrations would be requisite for the dyes as for the pig- 

 ments, and similar results might be anticipated from their investigation 

 as employed in native manufactures. 



11. Under this department of the Economic Geology of a country, 

 Department of Mi- are included the different kinds of mineral springs 

 neial Springs. or waters that may be found in it. These are im- 

 portant, not only as holding in suspension or combination certain 

 mineral products applicable to economical purposes, but also in their 

 scientific relations, and especially in their connection with the geologi- 

 cal structure of the district in which they may be found. The occur- 

 rence of mineral springs is almost invariably characteristic of the 

 action of disturbing forces, and it is in those districts, where such forces 

 have been most active, that they are found in the greatest abundance. 

 When they are thermal as well as mineral, their interest in a scienti- 

 fic point of view, is much increased ; and I may remark, it would be an 

 important contribution to the materials already collected for the in- 

 vestigation of the subject of interior terrestrial temperature, were the 

 thermal conditions of such springs of this class as either have been, 

 or may, yet be discovered in India, investigated with care, and in 

 detail. In the department under notice, are also included those 

 springs of petroleum, naphtha, or the impurer bituminous products 

 which have already been found in several parts of India, and which 

 we may hope to find in the North-Western Provinces also, when the 

 Himalayan coal fields have been more thoroughly examined. Spe- 

 cimens of all mineral springs, whether bituminous, chalybeate, sul- 

 phureous, alkaline, saline, or acidulous, that may be discovered in these 

 provinces, ought to be forwarded to the Museum, where they would 

 be examined, and their economic value ascertained. 



