At the age of twenty-four he was offered a professorship of astronomy at Oxford, which he modestly declined as being above his age, but afterwards accepted. His own astronomy was sadly deficient, for he supposed the circumference of our earth to be 216,000 miles. This, however, was before Sir Isaac Newton had published the true astronomy, or had himself learned it. After a most honorable career as teacher of science at Oxford, he received from the restored king, Charles II., the appointment of assistant to the Surveyor General of Works, an office which placed him in charge of public buildings in course of construction. It made him, in due time, the architect-general of England, and it was in that capacity that he designed and superintended very many of the long series of Works mentioned above. There never was a more economical appointment. The salary which he drew from the king appears to have been two hundred pounds a year, a sum equal perhaps to four thousand of our present dollars. Such was the modest compensation of the great architect who rebuilt London after the great fire. That catastrophe occurred a few years after his appointment. The fire continued to rage for nearly four days, during which it destroyed eighty-nine churches including St. Paul's, thirteen thousand two hundred houses, and laid waste four hundred streets. Christopher Wren was then thirty-five years of age. He promptly exhibited to the king a plan for rebuilding the city, which proposed the widening and straightening of the old streets, suggested a broad highway along the bank of the river, an ample space about St. Paul's, and many other improvements which would have saved posterity a world of trouble and expense. The government of the dissolute Charles was neither wise enough nor strong enough to carry out the scheme, and Sir Christopher was obliged to content himself with a sorry compromise. The rest of his life was spent in rebuilding the public edifices, his chief work being the great cathedral. Upon that vast edifice he labored for thirty-five years. When the first stone of it was laid, his son Christopher was a year old. It was that son, a man of thirty-six, who placed the last stone of the lantern above the dome, in the presence of the architect, the master builder, and a number of masons. This was in the year 1710. Sir Christopher lived thirteen years longer, withdrawn from active life in the country. Once a year, however, it was his custom to visit the city, and sit for a while under the dome of the cathedral. He died peacefully while dozing in his arm-chair after dinner, in 1723, aged ninety-two years, having lived one of the most interesting and victorious lives ever enjoyed by a mortal. If the people of London are proud of what was done by Sir Christopher Wren, they lament perhaps still more what he was not permitted to do. They are now attempting to execute some of his plans. Miss Lucy Phillimore, his biographer, says:--