4. In this method of close distillation; that is, where no space is allowed for evaporation; any one may easily invent many other experiments. And this we are certain of, that a suitable heat operating upon a body, without separating or consuming its parts, may produce wonderful effects and changes of structure*.

5. We might add, as an appendix to this pre cept, that some method should be discovered (which certainly is not difficult) whereby heat may operate, not only in a close, but in a tensile, or extensible vessel: which is the case in a very natural matrix, whether of vegetables or animals. For such an operation extends to many things, not performable by simple confinement. This contrivance does not regard the pygmy of Paracelsus, or any such monstrous trifles; but things of weight and solidity. For example, close distillation can never make a total conversion of water into oil; because oil possesses more space than water: but if the operation were performed in an extendible body: perhaps this transformation might be effected:

*It should seem that great light might be derived to philosophy from this kind of digestor, as there has been from the air pump, telescope, &c. See Dr. Papin's account of his digestor; and let the contrivance be improved, transferred, and varied; and a proper set of leading experiments be tried upon this, and other kinds of digestors.

which would be a thing of prodigious use; as all alimentation principally depends upon fat*.

6. It were a proper and very useful thing, sometimes in distillations to compel nature to an account; and take a just estimate of the quantity lost in the operation: that is, of the quantity grown pneumatical; and again of the remaining part, whether fixed or restored in the body. This may be done by first weighing the body to be distilled, and the vessels wherein the operation is to be performed; and after the ope ration is over, weighing the distilled liquor, the fæces, and lastly the vessels again: by which means may be learned what proportion was restored; what proportion remained in the fæces; and what adhered to the vessels; and the deficiency of the three several weights, compared with the weight of the whole body, will shew what proportion was rendered pneumatical.f

* See the Sylva Sylvarum, passim.

+ Something of this kind has been done by M. Lemery in his course of chemistry; but Mr. Hales in his Vegetable Staticks, has prosecuted the thing with great exactness; and more directly to the present purpose.

SECT. VI.

OF THE DILATATIONS AND RELAXATIONS OF BODIES BY THE REMISSION OF COLD.

TRANSITION.

WE proceed from the dilatations and rarifactions caused by actual heat, to the dilatations and relaxations produced by the remission of violent and intense cold: and this remission should be esteemed a comparative degree of heat.

1. Bodies froze by violent cold; but not so far as, by the continuance of the cold, to remain fixed in their condensation; open and restore themselves without manifest heat; and barely upon a remission of cold: as in ice, hail, snow, &c. but they do this much quicker upon the application of manifest heat.

2. But the more delicate substances, whose vigour consists in a subtile native spirit; as apples, pears, pomegranates, and the like; have their spirit suffocated by congelation; so as not again to recover their pristine vigour upon thawing.*

* Unless thawed by being put into cold water.

3. Wine likewise, and malt liquors, grow flat to the taste, and lose of their vigour upon freezing: yet they revive, relax, and as it were ferment again after thawing, when the weather becomes warm, and the wind southerly*.

SECT. VII.

OF THE DILATATION AND RELAXATION OF BODIES BY
POTENTIAL HEAT; OR THE AUXILIARY SPIRITS
OF OTHER BODIES.

TRANSITION.

As to the subject of potential heats, it is proper to consult the medicinal tables of secondary qualities; which exhibit the things that operate by dilatation, upon the human body: and they are in general such as these, viz.

1. Cardiacs, which dilate the spirits oppressed. 2. Abstergents, which strengthen the expulsive faculties.

3. Aperients, with regard to the orifices of the veins and vessels.

4. Aperients, with regard to the pores and passages of the parts.

The particulars wanting in this section, may in great measure be derived from Mr. Boyle's Experimental History of Cold.

5. Digestives, which ripen at the same time. 6. Digestives, which discuss at the same time; and,

7. Caustics, which burn and consume the flesh.

These things have their effect principally by dilating the spirits, humours, juices and the substance of the body, by means of auxiliary spirits; and again by a stimulating virtue which such medicines have in contact with the parts of the body, whether used internally or externally.

SPECULATION.

It appears from the weather-glass what an exquisite sense, or perception, the common air has of heat and cold; as immediately shewing the most subtile differences and degrees thereof. And we judge, that the perception of the spirits in animals, as to cold and heat, is much more acute and subtile: only the air is a pure and genuine pneumatic body, that has no tangible parts mixed among it; and the perception of the spirits is dulled and blunted by the tangible body in which they are detained. But notwithstanding this impediment, the spirits of living creatures, seem more delicate or sensible, than the air itself: for it has not hitherto appeared, that potential heat can cause a dilatation of the