C— GEOLOGY, 71 



Timely geological advice would have been useful in a recent case, in 

 connection with the excavation and exposure in a moist atmosphere of 

 carbonaceous shales, containing much marcasite— the more easily 

 decayable form of iron sulphide — occurring as large nodules or discoidal 

 masses. This material swells considerably on decay and induces 

 spontaneous combustion. Its use in the reclamation of a low-lying area 

 caused settlement of the surface till the marcasite was converted into 

 hydrous oxide of iron. 



Functions of a Geological Survey op a Colony. 



In considering this kind of geological survey it should be remembered 

 that it diflters greatly from the geological surveys of old countries in the 

 mode of operations necessary. 



The fact that it functions in a young, undeveloped and comparatively 

 unknown country, probably devoid of detailed maps, and with poor and 

 slow means of transport, compels it to adopt methods and undertake 

 duties entirely foreign to surveys long established. These surveys are 

 able to place at once, on accurate maps, while in the field, the geological 

 features of any district that is being examined. The geologist of the 

 Colony, however, has not the great benefit of such maps, nor usually 

 any reliable maps with good contours, and so, where field mapping in 

 detail has to be done, or special areas surveyed, a ground-work map has 

 to be made by himself. The collection of all information and the prepara- 

 tion of the topographical map involve the expenditure of by far the greater 

 portion of the time, labour, and expense of such a survey. This may 

 represent upwards of four-fifths of the time in certain types of country, 

 the geology of which is not of great variety. When comparing, therefore, 

 the character and production of maps and reports of a young colony with 

 those of Great Britain, due allowance should be made for these different 

 conditions. 



Opinions differ as to how the work is to be commenced. One geologist 

 may consider it advisable to make first a series of rapid reconnaissances 

 through the various districts, along natural boundaries such as the coast- 

 line, large rivers, main paths or roads, railways, if any, or through 

 promising belts of country ; then later a series of rapid cross-traverses 

 connecting with the first series, and later still numbers of others linking 

 the two series in various directions. This method enables him to get, in 

 the quickest manner, a general knowledge of the geology of the country as 

 a whole. The mapping, in detail, of the geology, in conformance with a 

 mathematical scheme of division of the country, can be done later as 

 opportunity offers. 



Another geologist may prefer to survey in detail certain areas, such as 

 a known mining field, a belt of country, or the main lines of communication, 

 leaving outlying districts for later work. 



Both methods have their advantages and disadvantages, but these can- 

 not be discussed in this address. The particular features of the country 

 and the wishes of the Government will determine the system of work. 



The following remarks indicate various activities of a survey of this 

 kind. 



