With the help of geologist Clarence Dutton, Steel organized a USGS expedition to study the lake in 1886. The party carried the "Cleetwood", a half-ton survey boat, up the steep slopes of the mountain then lowered it to the lake. From the stern of the "Cleetwood", a piece of pipe on the end of a spool of piano wire sounded the depth of the lake at 168 different points. Their deepest sounding, , was very close to the modern official depth of made in 2000 by sonar. At the same time, a topographer surveyed the area and created the first professional map of the Crater Lake area.