CONTENTS. 23 



Stewart Creek.- Hot spring. Siskiyou Mountains. Klamath River. Yreka. Little Scott s Mountains. Fort 



Jones. Lieut. Crook detained. Disappointment. Snow. Scott s Valley. Scott s Mountains. Trinity Valley. 



Trinity Mountains. Clear Creek. French Gulch. Shasta. Fort Reading again, and termination of field work. 



Lieutenant Williamson. Orders from War Department. Subsequent movements, &c. 



CHAPTER VI. 



Computation of Altitudes from Barometrical Observations. 



Preliminary Remarks. Instruments. Instrumental Errors. Interpolation and approximate test of accuracy in observers. 

 Corrections preparatory to computation : 1, for temperature of mercury ; 2, for instrumental errors ; 3, for horary 

 oscillation; 4, for abnormal oscillation. Method of computation, with remarks: 1, on the reading of the barometer 

 and thermometer at the lower station ; 2, on the reading of the thermometer at the upper station. Example.- Test 

 of the comparative accuracy of the different methods of computation, with tables showing the results obtained. 

 Height of Fort Reading ; explanation of tables of barometric observations in Appendix D, &c. 



CHAPTER VII. 



Eoute from Shasta Valley, East of Shasta Butte, to Fort Beading ; Explored by Lieut. It. S. 



Williamson, U. S. Top. Eng., in 1851. 



Explanation. Party. Yreka, in 1851. Start. View of two passes. Wright Lake. Water hole Porcupine killed. 

 Turned back. Pass. Extended view. Pumice-stone Difficult travelling. No water or grass. Natural bridge. 

 Pedregal. Water in fissure. Branch of Fall River. Fall River. Ford. Indians. Pit River. Tule raft. 

 Expedient. Pass through western chain of Sierra Nevada. Battle Creek. Cow Creek. Settlements. 



