As I was attentively examining a leaf of the Fantastical Tree, on which I perceived grand projects, and insufficient means; I saw another, so small and curled as to be almost invisible, fly off from a neighbouring bough, and suddenly disappear. At the same instant I felt a slight pricking in my forehead, and a sort of restlessness in my head, which I cannot describe, and which has not left me ever since. Certainly this leaf has entered my brain, and is labouring to unfold itself; some new invention will result from it one time or other. I even begin to 307suspect of what kind; and I imagine, it will be a mechanical affair. If I am not mistaken it is this:
The different tempers, the different talents, the different dispositions depend upon the heat and motion, more or less considerable, of the animal spirits: This is a settled point among the physicians; I shall not appeal from their judgment. The question would be to find a mechanical instrument, to discover in each person the degree of heat and motion of this animal liquid, in order to discern what any one is fit for, and to employ him accordingly. This is what I am seeking, and what the leaf, which is busy in my brain, when unfolded will not fail to show me.
308I will compose a quintessence analogous to the animal liquid; and, instead of spirits of wine, I will fill thermometers with it. On the side of the tube, in the room of the different degrees of the temperature of the air, there shall be an enumeration of the objects, about which men are usually employed: Instead of cold, temperate, hot, very hot, &c. shall be put, good for history, good for physick, good for poetry, good for the gown, good for the sword, good for the mitre, good for the baton, good for Bedlam, &c.
When a person shall put his hand upon the phial, the liquor will be condensed, or dilated; and, rising or falling 309in the tube, will show what the person is good for.
I will present Therm............