IN THE HAUNTS OF THE PAWNEES—LETTERS OF MRS. GEORGE DONNER—HALT AT FORT BERNARD—SIOUX INDIANS AT FORT LARAMIE.FOURTH OF JULY IN AN EMIGRANT PARTY—OPEN LETTER OF LANSFORD HASTINGS—GEORGE DONNER ELECTED CAPTAIN OF PARTY BOUND FOR CALIFORNIA—ENTERING THE GREAT DESERT—INSUFFICIENT SUPPLY OF FOOD—VOLUNTEERS COMMISSIONED BY MY FATHER TO HASTEN TO SUTTER'S FORT FOR RELIEF.CHAPTER IV