THIS fingular way of Thinking, led me to another new Thought, in proportioning the Magnitude of the Opening of Chimnies to thofe Rooms by an univerfal Rule, which will likewise serve for all Manner of Rooms whatever. By thefe Rules the Breadth of the Chimney, its Height, Depth, and Square of the Funnel for Conveyance of Smoke, are demonftrated, and in fo eafy a Manner, that none of you can mistake their Application and Use.

RULE I. To find the Height of the Opening of the Chimney from any given Magnitude of a Room, add the Length and Height of the Room together, and extract the Square Root of that Sum, and half that Root will be the Height of the Chimney.

RULE II. To find the Breadth of a Chimney from any given Magnitude of a Room, add the Length, Breadth and Height of the Room together, and extract the Square Root of that Sum, and half that Root will be the Height of Chimney.

your

RULE

RULE III. To find the Depth of a Chimney from any given Magnitude, including the Breadth and Height of the fame, add the Breadth and Height of the Chimney together, take one fourth of that Sum, and it is the Depth of the Chimney.

RULE IV. To find the Side of the Square of a Funnel proportion'd to clear the Smoke, from any given Depth of the Chimney, take three fourths of the given Depth, and that Sum is the Side of the Square of the Funnel.- Observe only, that in Cube Rooms the Height is equal to the Breadth, and the foregoing Rules are univerfal.

To prove the Rule univerfally useful, I have a Table of all the foregoing Proportions calculated in the preceding Manner, from which I fhall fhew you an Example of the Proportions of the fame, as is before defcrib'd, and in the following Manner.

If

The Double Cube

12,

24,

12,

3/9439

Chimnies.

I 71 2

THUS, Gentlemen, I have not omitted any Obfervation that might prove useful to you, especially in the ftrict Adherence to Proportions, perform'd by Rules. My next Lecture will contain fome useful Obfervations on Light fufficient to illuminate Rooms of any Magnitude, by an infallible Method; and fome general Reflections, which will prove of fingular Ufe to you, if observ'd, in the Performance of any Branch of Architecture.

GIVE me Leave, in the mean time, to affure you I am with due Respect,

Yours, &c.

LECTURE

LECTURE VII.

GENTLEMEN,

M

WY fifth and fixth Lectures confifted chiefly of the general Proportions which are requir'd to be made ufe of in the external and internal Parts of Building: When I confider Proportions, their Efficacy and Ufe, I am led into a Profundity of Thought; each Part of the Creation, confider'd diftinctly, or the amazing Structure of the Whole, or the Animal and Vegetable World, fills us with noble Ideas of the Power which fuch Proportions have on the Mind; I mean those that are made conformable to the un erring Laws of Nature.

If we immerse our Ideas into the in finite Tract of unbounded Space, and with the Imagination paint out the numberlefs Multitudes of Planets, or little

Worlds,