STRUCTURAL RESULTS OF FAULTING. 187 



deuces will often enable tlie prospector to determine on which side the 

 chimneys are to be found. On the barren sides evidences of crushing and 

 of closure of the fissure are i)robable. 



The fissure is more likely to have a constant dip (barring- the second- 

 ary offshoots) than a constant strike ; but, of course, irregularities in dip 

 like those in strike will open chambers which maybe productive. 



Offshoots into the hanging wall may occur at any depth, but none except 

 those near enough to the main cropping to reach the surface, where it 

 has a very considerable slope, are likely to be continuous. 



Application of theory to landslips. — Bcsidcs thc dccp-scated fissurcs produced by 

 profound disturbances of the earth's crust, there are comparatively super- 

 ficial phenomena which seem to come under the laws deduced in this chap- 

 ter. In regions where the soil is deep and covered with low-growing 

 vegetation, such as grass, the details of the topography are not molded by 

 the direct action of the rain, but by landslips ; oftentimes, indeed, of very 

 small extent, but repeated or increased year after year. The hanging wall 

 of such landslips commonly separates into distinct layers, as has been stated 

 in a preceding paragraph. These sheets must arrange themselves on the 

 locus 



if the arguments presented on p. 1()4, et seq., are correct. A yearly repeti- 

 tion of this action, sometimes modifying the hanging wall and sometimes 

 the foot wall of the slips, will eventually give the whole topography a log- 

 arithmic character; even the position of the gullies, and consequently the 

 lines of direct erosion, being determined as indicated on page 177. The simi- 

 larity between some of the logarithmic curves illustrated in this chapter and 

 the slopes of the gently-rounded hills common in grassy regions with 

 deep soil, needs only to be suggested. 



