84 PROGRESS REPORT, HYDROGRAPHY, 1893 AND 1894. Lbull.131. 
tion of this method is given in the Eleventh Annual Eeport of the 
United States Geological Survey, Part II, Irrigation, pages 10 to 18. 
It was reported that a number of complete measurements were made, 
but the results of these were not forwarded to the Washington office. 
These measurements were necessarily made rapidly, as the river is sub- 
ject to sudden rises on account of the warm rains falling on the snow in 
the mountains. Velocity observations were taken at every 20 feet 
across the river, and at intervals of 2 feet in the vertical, the meter 
being usually run for two minutes for each observation. Work at this 
point was continued until February 2, 1890. 
This station was inspected on January 8, 1895, by Mr. Arthur P. 
Davis, who at that time made a measurement of discharge, showing 
that for a height of 7.7 feet the river was flowing at the rate of 3,003 
second-feet. He states that the gage consists of a vertical plank pass- 
ing from the south side of the middle pier of the railroad bridge, and 
divided into feet and halves. It can be easily read from the south shore 
or from the wagon bridge, 200 feet to the west. The river measurement 
was made from the wagon bridge just below the railroad bridge. At 
that point the channel is sandy, but favorable for measurements at 
low water and at medium high stages. In extreme flood, however, the 
river leaves its banks. Mr. J. B. Lippincott states that the old gage 
on the Tuolumne was set in 1872 by A. P. Guppy and J. T. Eeed. 
The new gage, now standing in the river, set in 1889 by William P. 
Trowbridge, jr., reads 1 foot higher than the old gage; that is to say, 
2 feet on the old gage would read 3 feet on the new. 
Tuolumne Eiver, during the spring floods, has a daily variation, due 
to the melting of snow in the mountains. The low stage is at about £ 
a. m., and the high at about 3 p. m. J. T. Eeed, the present observer, 
records the height of water about 3 p. m. 
The velocity of the river at this point is largely controlled by the 
height of the San Joaquin, into which it empties. When the latter is 
low, and local rains occur in the Tuolumne, the velocity is relatively 
high ; that is to say, with the same height of gage different velocities 
may be observed. 
