278 Mr. T. Sop with, on the Application of Isometrical 



portion of the Mine. In like manner, the ground plan shows the relative 

 position of the horizontal workings, but gives no idea as regards their rela- 

 tive heights. The Holyfield Vein Level, which is ten fathoms higher than 

 the Sun Vein Level cannot be delineated otherwise than it would be if it 

 were exactly on the same plane with the other. 



If, therefore, it was deemed necessary to record the relative situation and 

 extent of these workings, several separate plans and sections would be 

 required, each of which would accurately represent one portion of the 

 Mine ; but from so many detached plans it would be difficult to form a 

 clear idea of the relative position of the whole. The clearness and sim- 

 plicity of the common ground plan and section arise from the circum- 

 stance, that one scale is applicable to every part and in every direction of 

 them, an advantage exceedingly great and which no other kind of projection 

 possesses. The disadvantages consist chiefly in the number of separate 

 drawings required, and the impossibility of showing with correctness any 

 objects that are not exactly on the plane represented or parallel with it. 



As a common plan and section is a surface viewed from an infinite dis- 

 tance, so also the isometrical projection varies from common perspective, in 

 supposing the eye placed at an infinite distance in that direction which 

 coincides with the diagonal of a cube produced. An interesting paper on 

 this mode of drawing, by Professor Farish, of Cambridge, is contained in 

 the Transactions of the Cambridge Philosophical Society, in which its nature 

 and application are elucidated by several examples. Professor Farish, who 

 was the first to point out the peculiar properties of Isometrical Drawing, 

 observes, that it may be advantageously employed for representing the 

 surface of mountainous countries and the geological features of a district. 

 As for the latter purpose it possesses several advantages, the object of the 

 present paper is to offer some illustration of its practical application to 

 geological and mining plans, accompanied with a descriptive notice of the 

 mining district selected as the subject of illustration. 



The manor of Alston Moor, so well known for its abundant produce of 

 mineral treasures, is hollowed by the Rivers Tyne and Nent into two prin- 

 cipal vallies, which unite near the town of Alston. The vale of Nent, 

 extending from this point of junction in a south-east direction for about 



