THE LODE. 279 



subterranean phenomena together render it, to my mind, altogether proba- 

 ble that the fissure is continuous, as shown upon the surface map. 



The evidence of the structure of the country on this section is, for the 

 most part, far less detailed than that obtained for some of the others; but 

 it is sufficient to justify considerable confidence in the general features 

 shown. The Forman shaft leaves nothing to be desired, thanks to the thor- 

 oughly scientific spirit in which the management has preserved accurately 

 labeled specimens from all levels, as well as temperature observations. A 

 very important point proved by the shaft is that the diabase does not extend 

 so far south as this line, for had it done so it must have been encountered 

 between the hornblende-andesite and the quartz-porphyry. The Caledonia 

 works were also open to inspection, and were carefully examined. The 

 three other shafts were closed, but the information afforded by the dumps, 

 in connection with the maps of the workings and the statements of employes 

 as to the drifts from which the different divisions of the dump-piles came, 

 and correlated with the data obtained on the surface and in the mines still 

 open, gave ample evidence as to the order of occurrence of the rocks. 



Diabase nowhere appears on this section, but is found overlying quartz- 

 porphyry at the Overman, a short distance to the north, and a small partial 

 section is given to illustrate this occurrence. 



Cross-section through the Union shaft. To the UOrth of the maiu LODE, aS tO the 



south of it, the evidences of dynamical and of chemical action grow slighter, 

 though mvich less rapidly. From the section through the Union shaft, for 

 example, it appears that on the main northerly branch no secondary fissure 

 has formed, and since the Lode is here divided at the surface into at least 

 three stringers, a sufficient intensity in the faulting action to produce a well- 

 marked secondary fissure could scarcely be anticipated. The south branch 

 of Seven-Mile Canon has cut deeply into the surface here pi-esented. If the 

 eroded ground were restored some traces of a logarithmic surface would be 

 visible. The lower workings from the Union shaft are entirely accessible, 

 and prove that the diabase contact is not on the fissui'e which has been 

 chiefly explored to tlie north of this plane, but diverges from the strike of 

 the main Lode towards the northeast. A line of heavy croppings exists in 

 this general direction, and probably marks the contact. A comparison of 



