Rocks and Minerals. Mr. Franklin gave me a piece of stone, which on account of its indestructibility in fire is used in New England for making smelting furnaces and forges. It consists of a mixture of Lapis ollaris or serpentine stone and of asbestos. The greatest part of it is a gray serpentine which is fat and smooth to the touch and is easily cut and worked. Here and there are some glittering speckles of that sort of asbestos whose fibres come from a center-like ray, or “star asbestos.” This stone is not found in strata or solid rocks, but is here and there scattered on the fields. ...

The salt which is used in the English North American colonies is brought from the West Indies, but it is more corrosive than the European....Mr. Franklin was of the opinion that the people in Pennsylvania could easier make good salt of sea water than in New England, where sometimes salt is made of the sea water on their coast, though their location is more northerly. ...

Asbestos. The mountain flax, or that kind of stone which Bishop Brovallius in his lectures on mineralogy published in 1739 calls Amiantus fibris separabilibus molliusculis, or the amiant with easily separable soft fibres, is found abundantly in Pennsylvania. Some pieces are very soft, others pretty tough. Mr. Franklin told me that twenty and some odd years ago, when he made a voyage to England, he had a little purse with him, made of the mountain flax of this country, which he presented to Sir Hans Sloane. I have likewise seen paper made of this stone, and I have received some small pieces of it which I keep in my cabinet. Mr. Franklin had been told by others that on exposing this mountain flax to the open air in winter, and leaving it in the cold and wet, it would grow together and become tougher and more suitable for spinning. But he did not venture to determine how well this opinion was founded. On this occasion he related a very amusing incident which happened to him with this mountain flax. He had several years ago gotten a piece of it, which he gave to one of his journeymen printers in order to get it made into a sheet at the paper mill. As soon as the fellow brought the paper, Mr. Franklin rolled it up and threw it into the fire, telling the journeyman he would see a miracle, a sheet of paper which did not burn. The ignorant fellow insisted upon the contrary, but was greatly terrified upon seeing himself convinced. Mr. Franklin then explained to him, though not very clearly, the peculiar qualities of the paper. As soon as he was gone, some of his acquaintances came in, who immediately recognized the paper. The journeyman thought he would show them a great curiosity and astonish them. He accordingly told them that he had curiously made a sheet of paper which would not burn, though it were thrown into the fire. They pretended to think it impossible, and he as strenuously maintained his assertion. At last they laid a wager about it, but while he was busy with stirring up the fire the others slyly besmeared the paper with fat. The journeyman, who was not aware of it, threw it into the fire and that moment it was all in flames. This astonished him so much that he was almost speechless, upon which they could not help laughing, and so disclosed the whole artifice.