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SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 



are said to have yielded well in early days, and would still be good hydraulic ground if the quan- 

 tity of gravel were sufficient to justify the necessary outlay for securing a supply of water. The 

 quantity, however, is very small. The region is attracting some attention from prospecters, and a 

 company of miners from Forest City, organized as the Forest City Consolidated Gold Mining Com- 

 pany, were making arrangements at the time of my visit to undertake the working of some of 



I 



these banks. 



The altitude of the lower end of the lava-How I made to be 3,469 feet, nearly 500 feet above 

 the present surface at Columbia Hill, and more than twice that amount above the bed-rock at 

 Badger Hill. The bed-rock exposed to view between the post-office at Columbia Hill and the lava, 

 is all slate. A comparison of the altitudes of this point and of the bed-rock at Montezuma Hill 

 shows the difference of level to be a little more than 1,100 feet. The distance in a direct line is 

 about five and a half or six miles, which would allow a grade of nearly 200 feet to the mile. If 

 any connection is to be traced between Montezuma Hill and the gravel higher up on the ridge, it 

 seems most probable that it will be found to be along this line. 



At least one effort has been made to reach, by means of a tunnel, the supposed channel under- 

 neath the lava. Eurisco Tunnel is between two and three miles from Columbia Hill in a direction 

 not far from N. 20° E. (magnetic). The mouth of the tunnel is in bed-rock, on the northern side 

 of the ridge, near the head of Grizzly Canon, and about 225 feet below the level of Bloody Run 

 ditch. The course of the tunnel is S. 40° E. (magnetic) for a distance of 400 feet ; then a change 

 of direction carries the tunnel to the southwest for a distance of three or four hundred feet farther, 

 and a second change to a more nearly south course carries it six or seven hundred farther still. 

 The " gravel" is struck shortly after the iirst change of direction near the upper end of an incline 

 raised about twenty feet through bed-rock. The altitude of this point is, according to my measure- 

 ments, 3,440 feet, nearly thirty feet lower than the bed-rock at the extremity of the lava-flow, — 

 a circumstance which surely does not point to any regular channel under the lava. The "gravel " 

 at Eurisco is also peculiar. Occasionally a quartz pebble, not much worn, was seen, but the greater 

 part of it was composed of slate or other metamorphic rock. The mass, as a whole, was remark- 

 able for its clayey character. A great many of the faces of the small pebbles and of the exposed 

 clay were slickensides, or, as the miners call it, "soapy." The deposit looked more like clay with 

 an occasional imbedded pebble, than like gravel with spaces filled with clay. Near the farther 

 end of the tunnel some large boulders are to be seen, which have not yet been completely un- 

 covered, some of them being as much as eight or ten feet across. There were also smaller boulders, 

 of two or three feet in diameter, of various kinds of rock. On the whole, the pebbles and boulders 

 presented angular rather than rounded surfaces. In the breasts only about three and a half feet in 

 thickness next the bed-rock has been removed. The deposit carries gold in small quantities, and 

 there is also carbonized wood. I do not see any reason to believe that there is any deep channel 

 there, but the deposit is interesting on account of its altitude and of its relation to some of the 

 projecting spurs of light-colored gravel, to which reference has been made above. 



The thickness of the lava capping between Columbia Hill and North Bloomfield is, on the 

 average, not far from 600 feet. The ridge to the northwest of Malakoff I found to be at its 

 highest part over 1,300 feet above the bed-rock at the mine. The precise position of the line of 

 junction between the lava and the underlying bed-rock was not easy to make out, but the above 

 estimate of 600 feet for the thickness of the lava must be nearly correct. There did not appear to 

 be any material differences of composition in different portions of the lava, though there are some 

 signs of a succession of flows. One of these signs is the existence of the projecting and prominent 

 outcrops of nearly horizontal layers, which appear to withstand the disintegrating action of atmos- 

 pheric agencies better than the rest of the mass. 





