Drilling temperature wells into the floor and rim of Kilauea Crater was a project I had anticipated when Mr. John Brooks Henderson of Washington came to Hawaii and offered to help finance it. We had taken the temperature of hot cracks in many places, and found them to range from 320° Centigrade at the Postal Card Crack close to Halemaumau, down to 96° Centigrade at Sulphur Bank, and then on to lower temperatures at many cracks which yielded visible vapor in damp weather but no vapor at all in sunshine. A spectacle for tourists was a crack on the Sulphur Bank flat, where a cigar to windward or the exhaust gas of a car would nucleate the invisible vapor and cause a big puff of white “steam” to show. This phenomenon, which depends on smoke particles condensing invisible water vapor, is well known at Solfatara near Naples. The experimental approach to finding out what the temperature of the ground really is, is to drill a hole and keep the temperature measured repeatedly with a thermometer, and to find out the thermal gradient change vertically if possible. This means to measure how much the temperature changes with depth. The whole problem concerns how much unusual heat energy is released at a place like Kilauea Crater. With the aid of Hobart, a drilling engineer, I started at Sulphur Bank with a churn drill. We quickly discovered that we were going through intensely hard basalt, containing metallic sulfide which appeared to be pyrite but turned out to be marcasite. After drilling for several years--with four holes at Sulphur Bank, one sixty-foot hole under the observatory shop, and about twenty-five holes in the eastern part of the Kilauea floor over a surveyed map pattern--we changed to a rotary core drill using steel shot, and then changed again to a percussion drill actuated by compressed air, for shallow holes to show cross-country temperatures. Unfortunately core drilling requires large quantities of water, which we did not have, for the Hawaii National Park depends upon rainwater collected from roofs in redwood tanks. Without water cooling, rotary bits heat and expand in hot rock, stick, and are often lost. Two seventy-foot holes, one at Sulphur Bank and the other in the middle of Kilauea floor, showed no definite thermal gradient; and in general it turned out that drill holes were dependent on steam in the cracks for their temperatures.