H. B. Medlicott—On Faults in Strata. 479 



groups A C, A' C ; and one in C". The chief dislocations are in 

 the groups C and A'. " If we had no other evidence of the physical 

 structure of the conglomerate than is supplied by the foregoing 

 systems of faults, we should be entitled to conclude that two systems 

 of elevating forces had acted, either simultaneously or in succession." 

 "The planes of the elevating forces were probably vertical planes, 

 nearly in the azimuths of 30° west of north, and 33° north of west." 

 The conjugate system A C was principally concerned in producing 

 the inner or latent structure ; while the system A' C was probably 

 the most powerful. " Both were concerned in producing the eleva- 

 tion of the beds, which have an average strike of east 35° north, 

 and an average dip of 13^^.42 south. The strike of the beds is thus 

 seen to be intermediate between the systems A and A', but lying 

 nearest to the former, which I conceive to have acted first in order 

 of time." " From the discussion of the planes of structure not 

 belonging to the two principal conjugate systems of the district, I 

 feel Little hesitation in coming to the conclusion, that there was at 

 least one more system of forces at work in producing the final 

 structure of the Old Eed Sandstone conglomerate :" the system A" 

 C" is represented by fourteen observations of planes having a mean 

 strike of 6° south of east, and twelve planes bearing 5° east of 

 north. There is one observation of a bearing east 15° north, the 

 solitary representative observed of the bearing conjugate to that of 

 C", which is represented by six readings having a mean strike of 

 north 15° west. " Although it is a single observation, I believe it 

 affords evidence (although not strong) of the probable existence in 

 this district of a fourth system of forces having acted upon the con- 

 glomerate beds." 



The foregoing statements illustrate, in the author's own words, 

 the conclusions he draws from the tabulation of his observations. 

 It may be remarked that much of the exactness, especially as 

 regards the minor systems, may be due to the arbitrary selection 

 of the range of the single groups ; thus, the single observation 

 in A'" is but 2° removed from the great group A ; and three 

 of the twelve observations in C" are much closer to the group A' 

 than to the nearest reading in C". These alterations would, how- 

 ever, only slightly affect the striking distinctness and correspondence 

 of the two principal conjugate systems. But the chief observation 

 to be made, with reference to the object of my paper, is upon the 

 purely abstract nature of the inferences that can be drawn from the 

 systems, as such : every properly geological inference (upon the 

 magnitude, direction, and succession of the phenomena) is based 

 upon independent evidence — the direction of upheaval of the strata, 

 the throw of the faults, the theory of cleavage and jointing. The 

 learned author of the paper is evidently not deceived on this point, 

 for in speaking even of the two main conjugate systems on their 

 own merits he says that the forces which produced them may have 

 acted either simultaneously or in succession. An unguarded reader 

 might, however, suppose that four '' systems of forces " represented 

 by four conjugate systems of fracture, indicated four periods of dis- 



