The mode in which this dispute was terminated is a striking proof of the high opinion entertained of Franklin's integrity and honour, even by those who considered him as inimical to their views. Nor was their confidence ill-founded. The assessment was made upon the strictest principle of equity; and the proprietary estates bore only a proportionable share of the expenses of supporting government.
After the completion of this important business, Franklin remained at the court of Great Britain as agent for the province of Pennsylvania. The extensive knowledge which he possessed of the situation of the colonies, and the regard which he always manifested for their interests, occasioned his appointment to the same office by the colonies of Massachusetts, Maryland, and Georgia. His conduct, in this situation, was such as rendered him still more dear to his countrymen.
He had now an opportunity of indulging in the society of those friends whom his merits had procured him while at a distance. The regard which they had entertained for him was rather increased by a personal acquaintance. The opposition which had been made to his discoveries in philosophy gradually ceased, and the rewards of literary merit were abundantly conferred upon him. The Royal Society of London, which had at first refused his performances admission into its transactions, now thought it an honour to rank him among its fellows. Other societies of Europe were equally ambitious of calling him a member. The University of St. Andrew, in Scotland, conferred upon him the degree of Doctor of Laws. Its example was followed by the Universities of Edinburgh and Oxford. His correspondence was sought for by the most eminent philosophers of Europe. His letters to these abound with true science, delivered in the most simple, unadorned manner.
The province of Canada was at this time in the possession of the French, who had originally settled it. The trade with the Indians, for which its situation was very convenient, was exceedingly lucrative. The French traders here found a market for their commodities, and received in return large quantities of rich furs, which they disposed of at a high price in Europe. While the possession of this country was highly advantageous to France, it was a grievous inconvenience to the inhabitants of the British colonies. The Indians were almost generally desirous to cultivate the friendship of the French, by whom they were abundantly supplied with arms and ammunition. Whenever a war happened, the Indians were ready to fall upon the frontiers; and this they frequently did, even when Great Britain and France were at peace. From these considerations, it appeared to be the interest of Great Britain to gain the possession of Canada. But the importance of such an acquisition was not well understood in England. Franklin about this time published his Canada pamphlet, in which he, in a very forcible manner, pointed out the advantages which would result from the conquest of this province.
An expedition against it was planned, and the command given to General Wolfe. His success is well known. At the treaty in 1762, France ceded Canada to Great Britain; and by her cession of Louisiana, at the same time, relinquished all her possessions on the continent of America.
Although Dr. Franklin was now principally occupied with political pursuits, he found time for philosophical studies. He extended his electrical researches, and made a variety of experiments, particularly on the tourmalin. The singular properties which this stone possesses, of being electrified on one side positively, and on the other negatively, by heat alone, without friction, had been but lately observed.
Some experiments on the cold produced by evaporation, made by Dr. Cullen, had been communicated to Dr. Franklin by Professor Simpson, of Glasgow. These he repeated, and found that, by the evaporation of ether in the exhausted receiver of an airpump, so great a degree of cold was produced in a summer's day, that water was converted into ice. This discovery he applied to the solution of a number of phenomena, particularly a single fact, which philosophers had endeavoured in vain to account for, viz., that the temperature of the human body, when in health, never exceeds 96 degrees of Fahrenheit's thermometer, although the atmosphere which surrounds it may be heated to a much greater degree. This he attributed to the increased perspiration and consequent evaporation produced by the heat.
In a letter to Mr. Small, of London, dated in May, 1760, Dr. Franklin makes a number of observations, tending to show that, in North America, northeast storms begin in the southwest parts. It appears, from actual observations, that a northeast storm, which extended a considerable distance, commenced at Philadelphia nearly four hours before it was felt at Boston. He endeavoured to account for this by supposing that, from heat, some rarefication takes place about the Gulf of Mexico; that the air farther north, being cooler, rushes in, and is succeeded by the cooler and denser air still farther north, and that thus a continued current is at length produced.
The tone produced by rubbing the brim of a drinking-glass with a wet finger had been generally known. A Mr. Puckeridge, an Irishman, by placing on a table a number of glasses of different sizes, and tuning them, by partly filling them with water, endeavoured to form an instrument capable of playing tunes. He was prevented, by an untimely end, from bringing his invention to any degree of perfection. After his death some improvements were made upon his plan. The sweetness of the tones induced Dr. Franklin to make a variety of experiments; and he at length formed that elegant instrument which he has called the Armonica.
In the summer of 1762 he returned to America. On his passage he observed the singular effect produced by the agitation of a vessel containing oil floating on water. The surface of the oil remains smooth and undisturbed, while the water is agitated with the utmost commotion. No satisfactory explanation of this appearance has, we believe, ever been given.