Lead-pencils.

Manufacturer and builder 2, 1869

Conrad Gessner, a Swiss naturalist of the sixteenth century, makes the first mention of graphite, as used in pencils, in his book on rare fossils. The nature of the material used in their manufacture was not then scientifically ascertained. Imparting a lead-color when traced upon paper, it was called black-lead. This name, however, is very inappropriate, as there is not  a trace of lead present in it. It was Pott who, in 1740, attempted to demonstrate this fact; but it still remains doubtful whether he was in possession of black-lead or of the sulphide of molubdena, which substance were then frequently confounded with each other. The Swedish professor, Scheele, in 1779, first distinguished them from each other in ascertaining the nature of both. He discovered that plumbago, when mixed with nitre, is converted into carbonic acid gas, this not being the case with the sulphide of molybdena.

Plumbago, or black-lead, (Reissblei, or drawing-lead, in German,) is more or less pure carbon, and occurs in beds and imbedded masses in gneiss, granite, micaschist, and various other rocks. Its principal impurity consists of oxide of iron. The purest variety of graphite occurs in Turkinsk, in the government of Irkutsk, in Siberia, where also a large mass has been found having the structure of the wood from which it was formed. This mine, however, has only recently been discovered. The purest variety was formerly obtained from the pits at the Borrowdale Mountains, in Cumberland. This is one of the reasons why the English pencils have won the fame which they still retain. Until very recently, in fact, they were considered quite indispensable to the work of fine drawing.