This prime duty done, we fell at once to our scientific tasks. The instrument-tent was set up, the mercurial barometer, taken out of its leather case and then out of its wooden case, was swung upon its tripod and a rough zero established, and it was left awhile to adjust itself to conditions before a reading was attempted. It was a great gratification to get it to the top uninjured. The boiling-point apparatus was put together and its candle lighted under the ice which filled its little cistern. The three-inch, three-circle aneroid was read at once at thirteen and two-tenths inches, its mendacious altitude scale confidently pointing at twenty-three thousand three hundred feet. Half an hour later it had dropped to 13.175 inches and had shot us up another one hundred feet into the air. Soon the water was boiling in the little tubes of the boiling-point thermometer and the steam pouring out of the vent. The thread of mercury rose to 174.9 deg. and stayed there. There is something definite and uncompromising about the boiling-point hypsometer; no tapping will make it rise or fall; it reaches its mark unmistakably and does not budge. The reading of the mercurial barometer is a slower and more delicate business. It takes a good light and a good sight to tell when the ivory zero-point is exactly touching the surface of the mercury in the cistern; it takes care and precision to get the vernier exactly level with the top of the column. It was read, some half-hour after it was set up, at 13.617 inches. The alcohol minimum thermometer stood at 7 deg. F. all the while we were on top. Meanwhile, Tatum had been reading a round of angles with the prismatic compass. He could not handle it with sufficient exactness with his mitts on, and he froze his fingers doing it barehanded. [Sidenote: The View]