162 APPENDIX D. GEOLOGY. 



of drift, containing small boulders, composed, as before, of greenstone 

 porphyry, quartz, and granite ; soil and subsoil arenaceous. 



May 11. — Formation the same as on yesterday ; saw strewn over the 

 surface a large quantity of redclish-brown and black calcareous rock, 

 containing carbonate of copper and small crystals of calcareous spar. 

 From the drift (which appears to be becoming more abundant and its 

 particles less rounded) I obtained specimens of chalcedony, jasper, and 

 carnelian. Soil and subsoil arenaceous, and of a reddish color. 



May 18. — Saw a number of deposites of soft, coarse granite, which 

 appeared to be undergoing rapid disintegration. The surface presented 

 large quantities of dark-colored and cellular igneous rock, composed 

 principally of silex and carbonate of lime ; soil and subsoil arenaceous. 



May 20. — Observed several clear springs bubbling up from beneath 

 the surface. Formation the same as before ; soil and subsoil arenaceous. 



May 21. — Met to-day with several sections of finely laminated sand- 

 stone of the same character as that before mentioned, with the exception 

 that the different laminae were thickly marked with small circular spots of 

 a green and yellow color. In several places I found it interstratified with 

 red clay. Near our encampment a fine section, showing an anticlinal 

 axis, the strata dipping east and west at an angle of three degrees, 

 exposed itself; over the surface were strewn large quantities of dark- 

 colored igneous rock of the same character as that seen on the 18th 

 instant. The drift was less abundant than before; soil and subsoil 

 arenaceous. 



May 22. — The surface was strewn in many places with detritus com- 

 posed of greenstone porphyry and granite ; soil and subsoil arenaceous. 



May 23. — Did not move from camp ; in the evening I explored Otter 

 creek, which at this point runs between bluff banks composed of red clay. 

 Its bed was thickly covered with drift, from which I obtained a number 

 of agates, and two small specimens of bluish-yellow quartz, each con- 

 taining a small particle of gold. By digging a few inches below the 

 drift, I reached a deposite of black ferruginous sand, which, upon being 

 stirred, emitted a strong odor of sulphuretted hydrogen gas. From the 

 creek I obtained a number of univalve and bivalve shells ; the latter 

 principally of the genus Unio. 



Captain Marcy having to-day visited several of the mountains, pre- 

 sented me with a number of specimens of soft granite of a reddish- 

 brown color, and of which the mountains appeared to be composed. 



May 25. — Remained in camp. This afternoon I measured with a 

 thermometer the temperature of Otter creek, and found it to be 72° F. 



