Part 2 (1/2)

LECTURE I

_The Introduction_

The object of experieneral, or more strictly, that of the properties of natural substances, and of the changes of those properties in different circue can only be attained by _experi hard bymade into bricks, and that by the same means lime-stone can be converted into quick-lime, and by the addition of water and sand, make mortar It is by observation also that we discover that stones and other heavy bodies fall to the ground, and that a net will attract iron In other words, experiation of the wisdom of God in the works and _the laws of nature_, so that it is one of the greatest objects to the mind of man, and opens a field of inquiry which has no bounds; every advance wenew doubts and subjects of farther inquiry

The uniformity we discover in the properties of natural substances enables us to lay down general rules, or principles, which, being invariable, we call the laws of nature; and by our knowledge of these lae are able to predict, and at our own pleasure to produce, particular results, and this is the source of all the powers of man It is the direction we acquire of the powers of nature; so that, as Lord Bacon observed, _knowledge is power_

All arts and manufactures are derived from science Thus the doctrine of _ravitation Every thing we are capable of doing by e of the properties of water in steae of the composition, and chemical properties, of that substance

Every new appearance in nature is preceded by so always attending it, we say that the appearance is _owing_ This circumstance we therefore call the _cause_, and the new appearance the _effect_ of that cause Thus we say that the union of phlogiston to a particular kind of earth is the cause of its beco a metal

It is one of the principal rules of philosophizing to admit no more causes than are necessary to account for the effects Thus, if the power of gravity, by which heavy bodies fall to the earth, be sufficient to retain the planets in their orbits, we are authorized to reject the _Cartesian Vortices_ In other words, we eneral propositions than are necessary to comprehend all the particulars contained in the observed that iron consists of a particular kind of earth united to phlogiston, and that it is soluble in acids; and that the same is true of all other metallic substances, we say, universally, that all iston, and that they are all soluble in soe in the properties of bodies, some are the addition of what are properly called _substances_, or things that are the objects of our senses, being _visible_, _tangible_, or having _weight_, &c Thus the addition of an acid changes an alkali into a neutral salt But other changes are occasioned either by a change of texture in the substance itself, or the addition of so that is not the object of any of our senses Thus, a piece of steel becolass acquires the property of flying asunder by a s when red hot into cold water Such also, in the opinion of some, is the difference between hot and cold substances

Till the nature of the cause be ascertained, it is convenient toboth of the above-e of properties in bodies Thus, whatever be the real cause of gravity, or of inflaravity_, or of _inflaravity to be occasioned by a fluid pervading the whole universe, which he termed _aether_, and whether inflammability be caused by the presence of a real substance called phlogiston, or not In this manner we use the letters _x_ and _y_ to denote unknown quantities in algebra

When changes are made in substances by the addition of other substances, they make what is called a _chemical union_; and in this case the properties of the compound cannot with any certainty be deduced from those of the component parts, but must be ascertained by fresh experirees of fusibility, of two metals, those of the compound cannot be predicted

Neither water nor acid of vitriol will separately dissolve iron, so as to produce inflaether will do it However, the properties of similar compounds are similar to one another Thus, all metals dissolved in acids are precipitated by mild alkalis This chemical union of two substances we ascribe to a certain _elective attraction_, or _affinity_ that subsists between them, in consequence of which they unite with one another whenever a proper opportunity offers, in preference to those substances to which they were before united Thus the vitriolic acid, having a stronger affinity with the vegetable alkali which is the basis of nitre, will unite with that alkali, and with it form another compound, called _vitriolated tartar_, while the acid of nitre, being detached from its base, is collected separately

When two substances coer affinity with either of the two parts than they have with each other, is added to them, it will unite with that part, and take its place in the solution, while the other will in many cases be precipitated, and may be collected Thus the earth of alum is precipitated from a solution of alum by salt of tartar This is the case of _simple affinity_

When both the substances are compounds, the component parts of which have a weaker affinity with each other than they have with those of the other compound, t combinations are formed, and this is called a case of _double affinity_ Thus when phlogisticated alkali is poured into a solution of green vitriol, the acid of the vitriol unites with the alkali, while the phlogiston joining the calx of ironopen to our investigation, we must consider the different parts in some order But it is not very in where ill, the properties of the substances we first treat of will be connected with those which es in one substance being occasioned by its union with another It will be impossible, for exa the _acids_, because by their union with acids very ies are made in their properties

There have been three principalnatural substances

One is according to the _three kingdoms_, as they are called, into which they have been distributed, viz the _etable_, and the _ani to the _elements_ which enter into their co to the _form_ in which they are usually found, viz _aerial_, _fluid_, or _solid_ Upon the whole this last appears to me to be the eneral observations concerning the other divisions when they are particularly wanted As there will be frequent occasion to speak of the component and elementary parts of all substances, I shall here observe, that, according to the latest observations, the following appear to be the elements which coisticated air_, or the _acidifying principle_; _phlogiston_, or the _alkaline principle_; the different _earths_, and the principles of _heat_, _light_, and _electricity_ Besides these, there are the following principles which have not been proved to be substances, viz

_attraction_, _repulsion_, and _netis to the present state of natural knowledge, to explain all the appearances that have yet occurred to us

LECTURE II

_Of the Properties of all Matter_

Before I consider the properties of particular substances, it will be proper to mention those which are common to them all But I shall first observe, that the term _substance_ has no proper idea annexed to it, but is merely a convenience in speech; since we cannot speak of the properties of substances, such as _hard_, _round_, _coloured_, &c &c

(which circuive proper ideas) without saying that they inhere in, or belong to, so_ and _person_ are also in the same predicament

One property of all substances is _extension_, since they all occupy some portion of space

The incapacity of any substance to change its place has been terh improperly, the _vis inertiae_ of matter It is sufficient to say, that neither this, nor any other effect can be produced without a cause