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. 
Boute from Shasta Valley, East of Shasta Butte, to Fort Reading; Explored by Lieut. R. 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. 
