תמונות בעמוד
PDF
ePub

and are loth that our own country should unite two follies in a publick work.

The architrave of Perault, which has been pompously produced, bears nothing but its entablature; and is so far from owing its support to the artful section of the stone, that it is held together by cramps of iron; to which I am afraid Mr.

M m ust have recourle, if he persists in his elliptis, or, to ule the words of his vindicator, forms his arch of four segments of circles drawn from four different centres. That Mr.

M o btained the prize of the architecture at Rome, a few months ago, is willingly confessed ; nor do his opponents doubt that he obtained it by deserving it. May he continue to obtain whatever he deserves; but let it not be presumed that a prize granted at Rome, implies an irresistible degree of skill. The competition is only between boys, and the prize given to excite laudable industry, not to reward consummate excellence. Nor will the suffage of the Romans much advance any name among those who know, what no man of science will deny, that architecture has for some time degenerated at Rome to the lowest state, and that the Pantheon is now deformed by petty decorations.

I am, Sir,

Yours, &c.

L E T T E R III.
SIR,

Dec. 15, 1759. IT is the common fate of erroneous positions, that

they are betrayed by defence, and obscured by explanation; that their authors deviate from the main question into incidental disquisitions, and raise a mist where they should let in light.

Of all these concomitants of errors, the Letter of Dec. 10, in favour of elliptical arches, has afforded examples. A great part of it is spent upon digressions. The writer allows, that the first excellence of a bridge is undoubtedly Arength ; but this concession affords him an opportunity of telling us, that strength, or provision against decay, has its limits; and of mentioning the Monument and Cupola, without any advance towards evidence or argument.

The first excellence of a bridge is now allowed to be Atrength ; and it has been asserted, that a semi-ellipsis has less strength than a semicircle. To this he first answers, that granting this position for a moment, the semi-ellipsis may yet have strength sufficient for the purposes of commerce. This grant, which was made but for a moment, needed not to have been made at all; for before he concludes his Letter, he undertakes to prove, that the elliptical arch must in all respects' be superior in strength to the femicircle. For this daring assertion he made way by the intermediate paragraphs ; in which he observes, that the convexity of a semi-ellipfis may be increased at will to any degree that strength may require; which is, that an elliptical arch may be made lefs elliptical, to be made less weak; or that an arch,

mi

which by its elliptical form is superior in strength to the semicircle, may become almost as strong as a semicircle, by being made almost femicircular.

That the longer diameter of an ellipsis may be Mortened, till it shall differ little from a circle, is indisputably true; but why should the writer forget the semicircle differs as little from such an ellipsis? It seems that the difference, whether small or great, is to the advantage of the seinicircle; for he does not pro- mise that the elliptical arch, with all the convexity that his imagination can confer, will stand without cramps of iron, and melted lead, and large stones, and a very thick arch; assistances which the semicircle does not require, and which can be yet less required by a semiellipsis, which is in all respects superior in strength.

Of a man who loves opposition so well, as to bę thus at variance with himself, little doubt can be made of his contrariety to others; nor do I think myself entitled to complain of disregard from one, with whom the performances of antiquity have so little weight : ret in defiance of all this contemptuous superiority, I must again venture to declare, that a strait line will hear no weight; being convinced, that not even the icience of Vajari can make that form strong which the Jaws of nature have condemned to weakness. By the pofition, that a strait line will bear nothing, is meant, that it receives no sirength from firaitness; for that many bocljes, laid in itrait lines, will support weight by the cohesion of their parts, every one has found, who has feen dishes on a Thelf, or a thief upon the gallows. It is not denied, that stones may be so cruthed together by enormous pressure on each side, that a hcavy mass

may safely be laid upon them; but the strength must be derived merely from the lateral resistance; and the line so loaded will be itself part of the load...

The semi-elliptical arch has one recommendation yet unexamined ; we are told that it is difficult of execution. Why difficulty should be chosen for its own sake, I am not able to discover; but it must not be forgotten, that as the convexity is increased, the difficulty is lefsened; and I know not well whether this writer, who appears equally ambitious of difficulty and studious of strength, will wish to increase the convexity for the gain of strength, or to lessen it for the love of difficulty.

The friend of Mr. M- , however he may be mistaken in some of his opinions, does not want the appearance of reason, when he prefers facts to theories; and that I may not dismiss the question withiout fome appeal to facts, I will borrow an example, suggested by a great artist, and recommended to those who may still doubt which of the two arches is the stronger, to press an egg first on the ends, and then upon the sides.

I am, SIR,

Yours, &c.

SOM E THOUGHTS

ON
AGRICULTURE,

Both Ancient and MODERN:
With an Account of the Honour due to an

ENGLISH FARMER *.

AGRICULTURE, in the primeval ages, was m the common parent of traffick; for the opulence of mankind then consisted in cattle, and the product of tillage; which are now very essential for the promotion of trade in general, but more particularly fo to such nations as are most abundant in cattle, corn, and fruits. The labour of the Farmer gives employment to the manufacturer, and yields a support for the other parts of a community: it is now the spring which sets the whole grand machine of commerce in motion; and the fail could not be spread without the aslistance of the plough. But, though the Farmers are of such utility in a state, we find them in general too much disregarded among the politer kind of people in the present age; while we cannot help observing the honour that antiquity has always paid to the profession of the husbandman: which naturally leads us into some reflections upon that occafion.

Though mines of gold and silver should be exhausted, and the species made of them loft; though • From the Vikter, for February 1756, p. 59.

diamonds

« הקודםהמשך »