Scientists first explored Crater Lake in 1883. Joseph Diller and Everett Hayden of the U.S. Geological Survey "tumbled logs over the cliffs to the water's edge, lashed them together with ropes to make a raft, and paddled over to the island." During the summer of 1886, Clarence Dutton and Mark Kerr, also of the USGS, along with William Steel, sounded the lake in a leaky rowboat at 168 scattered locations. Using piano wire to measure depth, the men recorded the lake's maximum depth at 1,996 feet. (11)

Attempts to measure the water level of Crater Lake began in 1892. Someone painted the name O. H. Herchberger and the date, September 10, 1892, at the waterline of a large rock projecting from shore, providing a crude bench mark for subsequent measurements. On August 1, 1897, F. V. Coville found the markings and reported that "the lower end of the 9 was 7 1/2 inches beneath the surface of the lake." A year earlier, on August 22, 1896, C. H. Sholes and Earl Wilbur of the Mazamas had installed a wooden gage along the shoreline, setting zero on the gage's scale exactly four feet below the lake surface. Concerned that the gage might be swept away by avalanching rocks or snow, W. W. Nickerson of Klamath Falls visited the gage-site on September 25, 1896, and inserted a bolt in a cliff about fifty feet west of the gage and five and three-fourths feet above the waterline. As predicted, the gage was broken off during the following winter and, according to Joseph Diller, "cast adrift on the lake." On September 14, 1961, after years of sporadic water-level measurements, the USGS installed a water-stage recorder in Cleetwood Cove. The instrument continues to operate today, recording lake-level changes in increments of 0.01 foot four times daily. (12)

Lake water temperature was first measured at Crater Lake in 1896. On August 22, Barton Evermann of the U.S. Fish Commission lowered a Negretti-Zambra deep-sea thermometer to the lake bottom. His measurements-60°F at the lake surface, 39°F at 555 feet, 41°F at 1,040 feet, and 46°F at 1,623 feet-indicated that the lake got warmer toward the bottom. Evermann concluded that "the waters of Crater Lake are still receiving heat from the rocks upon which they rest." But Diller was skeptical, arguing that the lake's bottom water should not be warmer since there was no evidence of volcanic heat emanating from the caldera floor; nor were there visible fumaroles or hot springs anywhere around the lake. In July 1901, Diller re-measured the lake's temperature gradient several times using two thermometers in tandem (the Negretti-Zambra instrument and an ordinary thermometer). He found that temperatures ranged from 52°F at the surface to a constant 39°F between about three hundred feet and the bottom. Based on these findings-which were later verified by temperature gradients recorded over the next seventy years-Diller concluded that the bottom of Crater Lake "contains no appreciable volcanic heat." (13)