36 RESOURCES OF CALIFORNIA. 
There was, then, a fall of three feet of water over an area of 
about twenty-two thousand five hundred square miles, and a 
fall of eight and a half feet over an area of fifteen thousand 
square miles. This would give us an average of five and one- 
fourth feet over an area of thirty-seven thousand five hundred 
square miles. The first foot was absorbed by the sand and 
earth, dried during a very arid summer and fall; and then 
there were four feet of water to escape through an outlet half 
a mile wide, from an area nearly as large as England, or the 
state of Ohio, 
The outlet proved insufficient: the waters heaped them. 
selves up in the lowest part of the Sacramento Basin, the size 
of which low portion I have already given as one hundred and 
fifty miles long and twenty wide, or an area of three thousand 
square miles. Now, four feet of water over an area of thirty- 
seven thousand five hundred square miles, will, if collected 
within three thousand square miles, form a body forty-eight 
feet deep; and that figure represents the amount of water that 
had to escape through the Sacramento River, below the mouth 
of the San Joaquin. It is to be observed that, as the outlet of 
the Sacramento Basin is in its centre, so the freshets come 
simultaneously from the north and from the south. The rains 
fall along the whole length of the Sierra Nevada at the same 
time; and as the mountain-streams are short and swift, they 
pour down their floods immediately and all together. Such 
are the circumstances which contributed to the great flood of 
1862, and may contribute to other floods in the future. 
During January, 1862, 24.36 inches of rain fell in San Fram 
cisco, according to records kept by Thomas Tennant, Esq. ; 
8.66 inches fell in Sacramento, according to Dr. T. M. Logan; 
37.79 inches fell at Downieville, according to Dr. T. R. Kibbe; 
and 33.79 inches fell in Grass Valley, according to Mr. Atwood. 
I presume that all these figures are correct save those for San 
Francisco; and while I admit the care and accuracy of Mr. 
Tennant, I must suspect that somebody played tricks with his 
gauge, upon which he could not keep a constant watch. 
