Geological Survey of Great Britain. 363 



are all on a scale of one inch to a mile. The tract having been 

 surveyed, the next duty is to construct horizontal sections for its 

 illustration. All the sections published by the survey are on a 

 true vertical and horizontal scale of six inches to a mile. The whole 

 country is levelled across with the level or the Theodolite, as the 

 case may be. By this means, the true form of the ground is ob- 

 tained, and it is then easy to delineate the actual thicknesses of 

 the various strata. The angles of some of these hills are so steep 

 that it requires bold men to climb them. In rare cases some of 

 the chainmen have refused to do so. After this is done for one 

 section the same is done for all parts of the country in an elaborate 

 manner. Professor Ramsay here explained the construction of 

 the maps which were hung up. He then stated that having com- 

 pleted these horizontal sections, the next step is to construct verti- 

 cal sections chiefly of the coal measures, and rarely of the other 

 ground. These are made on the scale of forty feet to an inch, and 

 give the precise thickness of the beds of coal in any coal field, and 

 the nature and thickness of the strata which contain them. Un- 

 derneath each bed of coal we have always fire clay — as I have no 

 doubt it is the case with you — filled with stigmaria. This, then, 

 is the general mode of procedure. But in the north of England, 

 in Ireland and in Scotland, a new scale of Ordnance survey has been 

 adopted. The whole of Ireland is surveyed upon a scale of six 

 inches to a mile, and Scotland and the north of England are being 

 surveyed upon the same scale. This large scale gives immense 

 facilities for accuracy of delineation, especially in the mining dis- 

 tricts. These six inch maps are sometimes contoured, the result 

 of which will be that when we come to construct a geological 

 section across the country, it will be much more easily done and 

 will, therefore, be a great saving of money and labour. In regard 

 to the Geological Survey, I cannot say that we trained and sent 

 out Sir "William Logan, for he was a trained Geologist before he 

 ever saw the survey, but others have been sent to other Provinces, 

 who are conducting important Geological surveys. The Director 

 of the Geological surveys of India, Professor Oldham, and all his 

 assistants, have either sprung from our Survey or the School of 

 Mines in Jermyn Street. The Director of the Survey of Australia, 

 the Colony of Victoria, Mr. Selwyn, and Mr. Wylie of the Cape of 

 Gcod Hope, also Mr. Hall, directing the Geological survey of Trin- 

 idad, were sent out from the Survey or the School of Mines. A 

 short time before coming here I was asked, in reference to a sur- 



