Contemporary with Basilius Valentinus were Isaac the Hollander and his son, who are supposed to have worked with success. They were the first alchemists of Holland, and their operations were highly esteemed by Paracelsus, Boyle, and Kunckel. In practical chemistry they followed the traditions of Geber, and their alchemical experiments are the most plain and explicit in the whole range of Hermetic literature. They worked principally in metals, describing minutely the particulars of every process. Their lives are almost unknown. “Buried in the obscurity necessary to adepts, they were occupied in the practice of the Hermetic science, and their study or laboratory was the daily scene of their industrious existence.”[T] They are placed in the fifteenth century by conjecture, from the fact that they do not cite any philosophers subsequent to that period. They speak of Geber, Dastin, Morien, and Arnold, but not of more modern authorities, while, on the other hand, their references to aquafortis and aqua-regiæ, which were discovered in the fourteenth century, prevent us from assigning their labours to an anterior epoch. The two Isaacs were particularly skilful in the manufacture of enamels and of artificial gem-stones. They taught that the Grand Magisterium could convert a million times its own weight into gold, and declared that any person taking weekly a small portion of the philosophical stone will be ever preserved in perfect health, and his life will be prolonged to the very last hour which God has assigned to him. The _Opera Mineralia Joannis Isaaci Hollandi, sive de Lapide Philosophico_ is a long and elaborate treatise on the one method of exalting the dead and impure metals into true _Sol_ and _Luna_. The first matter is said to be Saturn, or lead, and the vessels in which it is to be calcined and otherwise adapted to the purposes of aurific art, are plainly figured in illustrations introduced into the text. FOOTNOTES: [T] “Lives of Alchemysticall Philosophers.” Ed. of 1815. BERNARD TRÉVISAN. Bernard Compte de la Marche Trévisane is accredited by the popular legends of France with the powers of a sorcerer in possession of a devil’s bird or familiar spirit; nevertheless, he is called “the good,” and enjoyed a particular reputation for benevolence. Descendant of a distinguished Paduan family, Bernard Trévisan began to study the time-honoured science of alchemy about the time that Basil in Germany, and the two Isaacs in Holland were prosecuting their labours with supposed success. His father was a physician of Padua, where he himself was born in the year 1406. The account of his alchemical errors must rank among the most curious anecdotes in the annals of occult chemistry.