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 suspect 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.

I 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 in the tube, will show what the person is good for.

I will present Thermometers to sovereigns, that they may chuse Generals, Ministers, Counsellors, and especially Favourites, who will love them enough to tell them the truth. I will give some to Bishops to fill their Benefices and Dignities, for I observe, that those who are appointed to watch, should themselves be watched. I will give some to Fathers, that their children may be wisely disposed of: We shall not see them gird with a sword a son whom they ought to dedicate to the altar, nor bury in a cloister a daughter who would have been the delight of a husband, and the happiness of a family. I will give some to the Great, that they may discern those who deserve their protection: They will grant it no more to a base flatterer, to a supple intriguer, to an ostentatious mean person, who has pretensions; but to true merit, which is seldom seen by them, and never with all its advantages. I will give some to those tender-hearted virtuous Girls, made to enliven the small number of our pleasures, and to allay the multitude of our troubles. With my Thermometers, they will chuse husbands worthy of their affection, if any such there be; and they will not see themselves given up to men born for the plague of their sex; those men without morals, who marry for life, and espouse only for six months.

In fine, I will give some to particular persons, that each may examine himself, and act accordingly: For I observe, that generally every one does what he should not do; I see none but what are misplaced.

I am now solliciting for a pension, to defray the vast expence, that I must evidently be at in making Thermometers, even though I should give them only to such as most want them.

It is true, that reflection might serve instead of my liquid and glass-tubes, but reflections are known to be very rare. For example, it is now at Babylon as on the real stage; all is action, nothing is thought, and my Thermometers may become a necessary piece of furniture.