The discovery of oxygen, hydrogen, and many other gases, the isolation of aluminum, calcium, and other metals, showed that earth and air and water are not elements.

With an enterprise that can never be too much commended, advantage was taken of the transits of Venus, and, by sending expeditions to different regions, the distance of the earth from the sun was determined.

The step that European intellect had made between 1456 and 1759 was illustrated by Halley's comet.

When it appeared in the former year, it was considered as the harbinger of the vengeance of God, the dispenser of the most dreadful of his retributions, war, pestilence, famine.

By order of the pope, all the church-bells in Europe were rung to scare it away, the faithful were commanded to add each day another prayer; and, as their prayers had often in so marked a manner been answered in eclipses and droughts and rains, so on this occasion it was declared that a victory over the comet had been vouchsafed to the pope.