may always have wages for his labour; and is no lefs neceffary to his employer, than his employer is to him. While he looks for no protection from others, he is naturally roufed to be his own protector; and having nothing to abate his efteem of himself, he confequently afpires to the efteem of others. Thus every man that crowds our streets is a man of honour, difdainful of obligation, impatient of reproach, and defirous of extending his reputation among thofe of his own rank; and as courage is in most frequent ufe, the fame of courage is most eagerly purfued. From this neglect of fubordination I do not deny that fome inconveniencies may from time to time proceed: the power of the law does not always fufficiently supply the want of reverence, or maintain the proper diftinction between different ranks: but good and evil will grow up in this world together; and they who complain, in peace, of the infolence of the populace, must remember, that their infolence in peace is bravery in war.

CONSIDERATIONS

ON THE

PLANS offered for the Conftruction of BLACK-FRIARS BRIDGE.

In THREE LETTERS, to the PRINTER of the GAZETTEER.

SIR,

LETTER I.

Dec. 1, 1759.

L

THE Plans which have been offered by different architects, of different reputation and abilities, for the Conftruction of the Bridge intended to be built at Black-Friars, are, by the rejection of the greater part, now reduced to a finall number; in which fmall number three are fuppofed to be much fuperior to the reft; fo that only three architects are now properly competitors for the honour of this great employment; by two of whom are propofed femicircular, and by the other elliptical arches.

The question is therefore, whether an elliptical or femicircular arch is to be preferred?

The first excellence of a bridge built for commerce over a large river, is ftrength; for a bridge which cannot ftand, however beautiful, will boast its beauty but a little while; the ftronger arch is therefore to be preferred, and much more to be

preferred, if with greater strength it has greater beauty.

Those who are acquainted with the mathematical principles of architecture, are not many; and yet fewer are they who will, upon any fingle occafion, endure any laborious ftretch of thought, or harass their minds with unaccustomed investigations. We fhall therefore attempt to fhew the weakness of the elliptical arch, by arguments which appeal fimply to common reason, and which will yet ftand the teft of geometrical examination.

All arches have a certain degree of weakness. No hollow building can be equally ftrong with a folid mafs, of which every upper part preffes perpendicularly upon the lower. Any weight laid upon the top of an arch, has a tendency to force that top into the vacuity below; and the arch thus loaded on the top, ftands only because the ftones that form it, being wider in the upper than in the lower parts, that part that fills a wider space cannot fall through a space lefs wide; but the force which laid upon a flat would press directly downwards, is difperfed each way in a lateral direction, as the parts of a beam are pushed out to the right and left by a wedge driven between them. In proportion as the ftones are wider at the top than at the bottom, they can less easily be forced downwards, and as their lateral furfaces tend more from the center to each fide, to fo much more is the preffure directed laterally towards the piers, and so much less perpendicularly towards the vacuity.

Upon this plain principle the femicircular arch. may be demonftrated to excel in ftrength the ellip

tical arch, which approaching nearer to a strait line, must be conftructed with ftones whofe diminution downwards is very little, and of which the preffure is almoft perpendicular.

It has yet been fometimes afferted by hardy ignorance, that the elliptical arch is stronger than the femicircular; or in other terms, that any mafs is more strongly fupported the lefs it refts upon the fupporters. If the elliptical arch be equally strong with the femicircular, that is, if an arch, by approaching to a trait line, lofes none of its ftability, it will follow, that all arcuation is useless, and that the bridge may at laft, without any inconvenience, confift of ftone laid in ftrait lines from pillar to pillar. But if a ftrait line will bear no weight, which is evident at the first view, it is plain likewife, that an ellips will bear very little; and that as the arch is more curved, its ftrength is encreafed.

Having thus evinced the fuperior ftrength of the femicircular arch, we have fufficiently proved, that it ought to be preferred; but to leave no objection unprevented, we think it proper likewife to observe, that the elliptical arch muft always appear to want elevation and dignity; and that if beauty be to be determined by fuffrages, the elliptical arch will have little to boaft, fince the only bridge of that kind has now ftood two hundred years without imi

tation.

If in oppofition to thefe arguments, and in defiance at once of right reafon and general authority, the elliptical arch fhould at laft be chofen, what will the world believe, than that fome other mo

tive than reafon influenced the determination? And fome degree of partiality cannot but be fufpected by him, who has been told that one of the judges appointed to decide this queftion, is Mr. M-ll-r, who having, by ignorance or thoughtleffness, already preferred the elliptical arch, will probably think himself obliged to maintain his own judgment, though his opinion will avail but little with the publick, when it is known that Mr. S-p-n declares it to be falfe.

He that in the lift of the committee chofen for the fuperintendency of the bridge, reads many of the most illuftrious names of this great city, will hope that the greater number will have more reverence for the opinion of pofterity, than to dif grace themselves, and the metropolis of the kingdom, in compliance with any man, who, instead of yoting, afpires to dictate, perhaps without any claim to fuch fuperiority, either by greatnefs of birth, dignity of employment, extent of knowledge, or largeness of fortune.

SIR,

IN

LETTER II.

Dec. 8, 1759.

N questions of general concern, there is no law of government, or rule of decency, that forbids open examination and publick difcuffion. I fhall therefore not betray, by a mean apology, that right which no man has power, and, I fuppofe, no wife man has defire to refufe me; but fhall confider the Letter published by you laft Friday, in defence of Mr. M's defign for a new bridge.