At Cambridge he visited the chemical laboratory, with the distinguished Professor of Chemistry, Dr. Hadley. Franklin suggested that temperature could be astonishingly reduced by evaporation. It was entirely a new idea to the Professor. They both with others repaired to Franklin's room. He had ether there, and a thermometer. To the astonishment of the Professor of Chemistry in Cambridge University, the printer from Philadelphia showed him that by dipping the ball into the ether, and then blowing upon it with bellows to increase the evaporation, the mercury rapidly sunk twenty-five degrees below the freezing point. Ice was formed a quarter of an inch thick, all around the ball. Thus, surrounded by the professors of one of the most distinguished universities of Europe, Benjamin Franklin was the teacher of the teachers.
The father and the son visited the villages where their ancestors had lived. They sought out poor relations, and examined the tombstones. In the spring of 1769, they spent six weeks in Scotland. The University of St. Andrews conferred upon Franklin the honorary title of doctor, by which he has since been generally known. Other universities received him with great distinction. The corporation of Edinburgh voted him the freedom of the city. All the saloons of fashion were not only open to receive him, but his presence, at every brilliant entertainment, was eagerly sought. The most distinguished men of letters crowded around him. Hume, Robertson and Lord Kames became his intimate friends.
These were honors sufficient to turn the head of almost any man. But Franklin, who allowed no adversity to annoy him, could not be unduly elated by any prosperity or flattery.
"On the whole," writes Franklin, "I must say, that the time we spent there (Scotland) was six weeks of the _densest_ happiness I have met with in any part of my life."
Still it is evident that occasionally he felt some slight yearnings for the joys of that home, over which his highly esteemed wife presided with such economy and skill. He wrote to her,
"The regard and friendship I meet with from persons of worth, and the conversation of ingenuous men give me no small pleasure. But at this time of life, domestic comforts afford the most solid satisfaction;[20] and my uneasiness at being absent from my family and longing desire to be with them, make me often sigh, in the midst of cheerful company."