UNSTRATIFIED CONDITION. 



Ill 



Fig. 123. A vein a faulted by b, — whence it is inferred that b is subsequent to a 

 an age. Also a vein 1 faulted by 2, and again by 3, and 3 faulted by 4; 2 and 3, 



therefore, were subsequent in age to 1, and 4 was subsequent to 3. The faulting is 

 ■exhibited also in the laj-ers of the stratified rocks which the veins intersect. 



Fig. 125. Fig. 126. 



Figs. 124, 125, 126. Veins much broken or faulted: in 124, four faults within a 

 length of eighteen inches: in 125, six faults in six feet; in 126, the broken parts of the 

 'vein of unequal breadth. 



Fig. 128. 



Fig. 129. 



Figs. 127, 128, 129. Other faulted veins: 127 a and b, six feet apart, and still 

 different in their faults; 128, 129, other interrupted v,eins. These dissimilarities be- 

 tween the parts of one faulted vein, as in 126, and between the parts of two parallel 

 veins, as in 127, arise from an oblique shove of the parts, either at the time of the 

 fracturing in which the veins themselves originated, or at some subsequent fracturing. 



The points illustrated in the preceding figures are, — 

 The great irregularities of size in veins along their courses, swell- 

 ing out and contracting ; their occasional reticulations ; their fre- 

 quently embracing portions of the enclosed rock ; their numerous 

 faultings, or breaks and displacements. 



(4.) Structure. — Dikes. — Dikes consist essentially of the same 

 kind of material from side to side and at all heights, where not 



