Correspondence — Mr. A. F. Griffith. , 429 



alteration. Of course Figure 9 is generalized, and tlie details might 

 be varied ; as, for instance, by some of the faults bifurcating or by 

 step faults. 



I think it possible that "our science " is more in danger of " losing 

 caste " by the Professor's critique, than by my article. It seems to 

 be the especial misfortune of Geolog}^ that questions relating to 

 it cannot be discussed dispassionately — I had almost written with 

 courtesy. I can only hope that some of your readers have under- 

 stood my meaning better than Mr. Blake has done. 0. Fisher. 



Fig. 9. 

 Fig. 8. 



13 Aug. 1881. 



EEPLY TO PROF. BLAKE'S CRITICISM ON FAULTS. 

 Sir, — Having been much interested in the two suggestive papers 

 by my friend Mr. Fisher on the subject of Faulting, Jointing and 

 Cleavage, lately published in this Magazine, I was naturally some- 

 what surprised at being told last month, on the authority of Prof. 

 Blake, that the papers in question were a " mischievous " compound 

 of mere " chaff." I have, therefore, carefully gone over the original 

 papers again (including the equations which the Professor condemns 

 as erroneous), with Prof. Blake's article as a guide ; the result being 

 that the whole of the long and somewhat violent criticism shows 

 itself to be a mixture of errors and misapprehensions so extraordinary 

 as to make one wonder what the Professor can have been about in 

 writing such an article for publication. He certainly points out 

 the obvious error in Figs. 8 and 9 ; but even in doing this he has 

 allowed himself to fall into the mistake of giving an obviously 

 imaginary reason for this error. The figures are easily corrected ; 

 and when this is done, it will be seen that there is no need for 

 any correction in the text, nor any alteration in the argument; so 

 far is it from being true, as the critic asserts, that the error in the 

 figures is " the result of attempting to form faults " either in the 

 way suggested by Mr. Fisher, or in the parody thereof suggested 

 by the critic. Again, on p. 212, 1. 26, Mr. Fisher has omitted the 

 letter x after A, (unless, indeed, he here uses the symbol X mei'ely 

 to identify the force spoken of, which appears to me the probable 

 explanation). This, which is at worst a mere clerical error, cannot 

 have caused any confusion except perhaps in the critic's mind. But 

 Prof. Blake has seized the opportunity to " run full tilt " at the 

 whole paper in consequence. One other criticism offered by Prof. 

 Blake may appear to some to be of some weight, when he doubts 

 (on p. 368) whether Mr. Fisher is right in assuming that the resis- 



