JT. B. Medlicott — On Faults in Strata. 477 



obaervations. There are, no doubt, self-evident objections to the 

 theory as it stands, such as the repeated recurrence of disturbance 

 along the same lines of fissure at remote intervals of time ; or, the 

 production of intersecting fissures by one and the same force. 

 There is even room for ridicule in the paternal weakness with which 

 almost irrelevant phenomena are attempted to be affiliated and en- 

 tangled in the cords of the reseau pentagonal by its venerable author. 

 But such critique de tendence may be left to those who have only 

 words to discuss ; what is wanted is to know how much truth there 

 is in this great idea — whether in geological or in primitive times (for 

 men are returning to a belief in a primitive earth), great phenomena 

 of disturbance were subjected to any recognizable law of form ; and 

 whether in order of succession these resulted in any symmetry of 

 distribution, pentagonal or otherwise. It may indeed be that the very 

 complexity and elasticity of this system, admitting perhaps of its 

 being framed and supported by a plausible amount of evidence, 

 through its adaptability to almost any evidence, should present a 

 corresponding difficulty to any sufficient refutation ; so that we may 

 have to leave it to time to settle its merits. This is at least a con- 

 venient opinion for those to adopt who have neither the power nor 

 the opportunity to undertake a full discussion of the subject. And 

 it is no small consolation for such humbler workers to know that 

 the intelligent observation of rock-structure in the field is the most 

 useful way of contributing to the solution of those great problems. 

 It was in this sense that I ventured, in my former paper on faults, to 

 give warning against the temptation to an easily secured semblance of 

 finish by systematizing structural features according to direction, with- 

 out a due preliminary investigation of the other more essential characters 

 — the special and the local significance of the things so classified. 



I will attempt to illustrate the meaning and force of my remark 

 by a brief discussion of the recent endeavour, on the part of a dis- 

 tinguished British geologist, to give an independent value to 

 the element of direction. Professor Haughton's studies on joint- 

 systems and their mechanical origin (Phil. Trans, for 1858 and 

 1864) are more searching than the wider system of De Beaumont; 

 they take up details of structure that the latter author apparently 

 found convenient to overlook. The speculations are based upon the 

 discussion of a large collection of data, and are altogether most 

 instructive ; but in so far as applicable to practice they seem to me 

 vague and uncertain ; by which I mean that they would scarcely, if 

 at all, lighten the burthen of observation to be undertaken in the 

 investigation of a new field, by enabling one to draw any safe 

 inference upon the more easily obtained evidence. 



The leading facts of this inquiry have long been familiar to ob- 

 servers : — that in every region of disturbance certain directions of 

 strike are predominant, and that disturbances are of different ages. 

 The object of further researches has been to ascertain the limits of 

 the various efiects of disturbance, and to discover any order in them, 

 or in the relations of the general systems to each other. 



Professor Haughton's first and most completely worked example 



TOL. VII.— NO. LXXYI. 31 



