C— GEOLOGY. 77 



— and that he may be compelled to wait for the result of boring done at 

 spots indicated by him. Therefore, it is advisable that a geological report 

 should precede the efforts to obtain permanent water supplies, and not, as 

 so frequently happens, be asked for after one or more costly attempts 

 have failed. 



There are many examples in the Colonies of great waste of money in 

 this manner, one case in which £20,000 was entirely wasted. A boring 

 engineer usually has no knowledge of geology, or of the connection between 

 stratigraphy and water supply, so he cannot be expected to do more than 

 the mechanical part of the work. 



Public Works. — To this department, perhaps, more so than to any 

 other, the geological survey can be of assistance, specially with regard to — 



(1) The discovery of rocks, suitable for constructional purposes (such 

 as for houses, bridges, drains, macadam), and of limestone, for 

 lime, mortar, concrete, cement and house-washes. 



(2) The character of the foundations for bridges, large buildings, 

 dams and breakwaters. 



(3) The nature of the rocks in areas where new roads are to be made. 

 This is mainly for possible variations of route with reduction of 

 expense in construction and maintenance. 



In country without outcrops of wide-spread suitable rocks, the help of 

 the geologist is necessary to ascertain if any suitable ones occur as dykes 

 or as beds among other folded unsuitable ones. If they do, then he can 

 possibly trace their extensions into other localities. 



In tropical climates, such as almost all our Colonies possess, the 

 question of suitable road-metal becomes a pressing one. For this 

 purpose it is advisable to get, if possible, rocks, such as dolerite, and 

 gabbro, that are tough and hard, do not fracture naturally, but on abrasion 

 yield a binding material, such as lime and iron, which under the action of 

 intermittent saturation and evaporation becomes a cement. 



The case of Jamaica may be cited where Dr. Matley, in the course of 

 his geological investigations found many dykes of basic rocks eminently 

 suitable for macadam and available for replacement of the limestone^a 

 much inferior rock — then being used in the Colony. The attrition of 

 limestone is so rapid that it is usually found to be unsuitable for roads 

 with heavy traffic, but for light traffic it is excellent. 



The search for limestone is an important duty of the geologist and 

 should be continued until su2)plies of good limestone have been obtained, 

 or failing that, till it seems quite unlikely that any such rocks exist in the 

 country. A good limestone, if properly treated during the burning stage 

 should produce good lime, and unless in remote districts under conditions 

 of costly transport and burning it should be cheaper to produce it locally 

 than to import it at great cost. 



Quartzite, quartz-schist, and hornstone are used largely in some 

 countries, but the excessive wear of tyres, the brittleness of the rocks, the 

 serious effect of hard sharp-edged particles of dust on the lungs, the non- 

 binding character of the material — all are against the use of this type of 

 stone, despite the lower cost of excavation and breakage. 



Hydro- Electric Power. — This question may be regarded as quite outside 

 the duties of a geologist. A little consideration, however, will show that 



