[Illustration:  SECTION OF FUNNEL-SHAPED SPRING.

SHOWING HOW BRANCHES AND TWIGS LODGE AT THE POINT OF CONVERGENCE SO AS
TO MAKE A FOUNDATION FOR GRASS AND EARTH UNTIL THE SPRING IS FILLED TO
THE TOP AND THE SURFACE IS COVERED WITH A LIVING TURF STRONG ENOUGH TO
BEAR A CONSIDERABLE WEIGHT.]

Lieutenant Doane was much amazed at the appearance of my horse’s legs, upon our return from Brown mountain, and has asked General Washburn and myself what can be the nature of the ground where such a mishap could occur.  My theory of the matter is this:  We frequently found springs of hot water—­though not boiling—­some fifteen or twenty feet in diameter at the top, the sides of which were funnel-shaped, and converged to a narrow opening of say three feet diameter at a depth of twelve or fifteen feet, and which below the point of convergence opened out like an hour glass.  In some of these springs at the point of convergence we found tree branches that had fallen into the spring and had become impregnated with the silica or lime of the water; water-soaked we call it.  I saw a number of such springs in which several branches of trees were lying across the small opening at the point of convergence.  When once these are firmly lodged, they form a support for smaller branches and twigs, and thus the tufts of grass which the spring floods or melting snows bring down from the sides of the mountain will, after a few years, made a sufficiently strong foundation for the earth, which will also wash down the slopes into the spring.  Once a firm footing is established, it is only a question of time when the spring will be filled to the brim with earth.  Then gradually the seed blown over the surface of the spring from the weeds and grass near by will take root, and, in the course of a few years, a strong turf will be formed, through which the water may percolate in many places, though giving to the unsuspecting traveler no sign of its treacherous character.  I think that it was through such a turf as this that the fore legs of my horse and my right hand were plunged.[T]

[Illustration:  BREAKING THROUGH THE TURF, FORMED OVER THE SURFACE OF SUCH A SPRING AS THAT SHOWN ABOVE.]

My pack horse which I rode to-day, a buckskin colored broncho, which is docile under the pack saddle, “bucked” as I mounted him this morning; but I kept my seat in the saddle without difficulty.  Walter Trumbull, however, on my return to-night, presented me with a sketch which he says is a faithful portrayal of both horse and rider in the acrobatic act.  I think the sketch is an exaggeration, and that I hugged the saddle in better form than it indicates.

[Illustration:  MY BUCKING BRONCHO.]

Tuesday, September 13.—­It was Jake Smith’s turn to stand guard last night, but he refused to do so, and Washburn took his place.