This article analyzes the relation between Francis Bacon’s Sylva sylvarum one of its most important sources, Giovan Barttista Della Porta’s Magia naturalis . I claim that Bacon used Della Porta’s experimental reports as a basis upon which he built his science of metaphysics and natural magic. Since Della Porta’s interest lies in the immediate transformation of individual bodies, Bacon considers his approach an inferior kind of science, what he called physics mechanics. There are several changes Bacon made to Della Porta’s experimental reports. They can be grouped by addition of causal explanations, generalizations, selection reordering of instances under different headings. Through all these transformations, Bacon acquires a more profound knowledge of nature and its inner activities and takes Della Porta’s experimental reports to the “superior” science of metaphysics and natural magic.