Benjamin Franklin; Self-Revealed, Volume 2 (of 2) / A Biographical and Critical Study Based Mainly on his own Writings

by Wiliam Cabell Bruce

The production of cold by evaporation was another subject which enlisted the eager interest of Franklin. In co-operation with Dr. Hadley, the Professor of Chemistry at Cambridge, England, he was so successful in covering a ball with ice by wetting it from time to time with ether, and blowing upon the ether with a bellows, that he could write to John Lining in these words: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day, if he were to stand in a passage through which the wind blew briskly, and to be wet frequently with ether, a spirit that is more inflammable than brandy, or common spirits of wine."

Geology was in its infancy during Franklin's time, but he hazarded some conjectures about the formation of the earth that are perhaps not less trustworthy than those advanced by riper geologists. In the letter, in which these conjectures were communicated to the Abbé Soulavie, he said:

Part of the high county of Derby being probably as much above the level of the sea, as the coal mines of Whitehaven were below it, seemed a proof that there had been a great bouleversement in the surface of that Island (Great Britain), some part of it having been depressed under the sea, and other parts which had been under it being raised above it.... Such changes in the superficial parts of the globe [he continued] seemed to me unlikely to happen if the earth were solid to the centre. I therefore imagined that the internal parts might be a fluid more dense, and of greater specific gravity than any of the solids we are acquainted with; which therefore might swim in or upon that fluid. Thus the surface of the globe would be a shell, capable of being broken and disordered by the violent movements of the fluid on which it rested.

The letter contains other speculations equally bold:

It has long been a supposition of mine that the iron contained in the substance of this globe, has made it capable of becoming as it is a great magnet. That the fluid of magnetism exists perhaps in all space; so that there is a magnetical North and South of the universe as well as of this globe, and that if it were possible for a man to fly from star to star, he might govern his course by the compass. That it was by the power of this general magnetism this globe became a particular magnet. In soft or hot iron the fluid of magnetism is naturally diffused equally; when within the influence of the magnet, it is drawn to one end of the Iron, made denser there, and rare at the other, while the iron continues soft and hot, it is only a temporary magnet: If it cools or grows hard in that situation, it becomes a permanent one, the magnetic fluid not easily resuming its equilibrium. Perhaps it may be owing to the permanent magnetism of this globe, which it had not at first, that its axis is at present kept parallel to itself, and not liable to the changes it formerly suffered, which occasioned the rupture of its shell, the submersions and emersions of its lands and the confusion of its seasons.

It was probably, Franklin thought, different relations between the earth and its axis in the past that caused much of Europe, including the mountains of Passy, on which he lived, and which were composed of limestone rock and sea shells, to be abandoned by the sea, and to change its ancient climate, which seemed, he said, to have been a hot one.

The physical convulsions to which the earth had been subject in the past were, however, in his opinion beneficent.

Had [he said in a letter to Sir John Pringle] the different strata of clay, gravel, marble, coals, limestone, sand, minerals, &c., continued to lie level, one under the other, as they may be supposed to have done before these convulsions, we should have had the use only of a few of the uppermost of the strata, the others lying too deep and too difficult to be come at; but the shell of the earth being broke, and the fragments thrown into this oblique position, the disjointed ends of a great number of strata of different kinds are brought up to-day, and a great variety of useful materials put into our power, which would otherwise have remained eternally concealed from us. So that what has been usually looked upon as a ruin suffered by this part of the universe, was, in reality, only a preparation or means of rendering the earth more fit for use, more capable of being to mankind a convenient and comfortable habitation.

The scientific conjectures of Franklin may not always have been sound, but they are invariably so readable that we experience no difficulty in understanding why the Abbé Raynal should have preferred his fictions to other men's truths.