ENGLISH COMMON SOLDIERS

15

arts; he may always have wages for his labour; and is no less necessary to his employer, than his employer is to him. While he looks for no protection from others, he is naturally roused to be his own protector; and having nothing to abate his esteem of himself, he consequently aspires to the esteem of others. Thus every man that crowds our streets is a man of honour, disdainful of obligation, impatient of reproach, and desirous of extending his reputation among those of his own rank; and as courage is in most frequent use, the fame of courage is most eagerly pursued. From this neglect of subordination I do not deny that some inconveniencies may from time to time proceed: thepower of the law does not always sufficiently supply the want of reverence, or maintain the proper distinction between different ranks: but good and evil will grow up in this world together; and they who complain, in peace, of the insolence of the populace, must remember, that their insolence in peace is bravery in war.

CONSIDERATIONS

ON THE

PLANS OFFERED FOR THE CONSTRUCTION

OF

BLACKFRIARS BRIDGE.

In THREE LETTERS, to the PRINTER of the GAZETTEER.

LETTER I.

SIR,

Dec. 1. 1759.

THE plans which have been offered by different architects, of different reputation and abilities, for the Construction of the Bridge intended to be built at Blackfriars, are, by the rejection of the greater part, now reduced to a small number; in which small number three are supposed to be much superior to the rest; so that only three architects are now properly competitors for the honour of this great employment; by two of whom are proposed semicircular, and by the other elliptical arches. The question is, therefore, whether an elliptical or semicircular arch is to be preferred?

The first excellence of a bridge built for commerce over a large river, is strength; for a bridge

which cannot stand, however beautiful, will boast its beauty but a little while; the stronger 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 single occasion, endure any laborious stretch of thought, or harass their minds with unaccustomed investigations. We shall therefore attempt to shew the weakness of the elliptical arch, by arguments which appeal simply to common reason, and which will yet stand the test of geometrical examination.

All arches have a certain degree of weakness. No hollow building can be equally strong with a solid mass, of which every upper part presses 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, stands only because the stones 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 less wide; but the force which laid upon a flat would press directly downwards, is dispersed 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 stones are wider at the top than at the bottom, they can less easily be forced downwards, and as their lateral surfaces tend more from the centre to each side, to so much more is the pressure directed laterally towards the piers, andsomuch less perpendicularly towards the vacuity.

18

CONSIDERATIONS ON THE

Upon this plain principle the semicircul may be demonstrated to excel in strength th tical arch, which approaching nearer to a line, must be constructed with stones whos nution downwards is very little, and of whi pressure is almost perpendicular.

It has yet been sometimes asserted by ha norance, that the elliptical arch is stronger th semicircular; or, in other terms, that any n more strongly supported the less it rests up supporters. If the elliptical arch be equally with the semicircular, that is, if an arch, b proaching to a strait line, loses none of its sta it will follow, that all arcuation is useless, that the bridge may at last, without any ind nience, consist of stone laid in strait lines fro lar to pillar. But if a straight line will be weight, which is evident at the first view, plain likewise, that an ellipsis will bear very and that as the arch is more curved, its streng increased.

Having thus evinced the superíor strength semicircular arch, we have sufficiently proved, it ought to be preferred; but to leave no objeunprevented, we think it proper likewise to obs that the elliptical arch must always appear to elevation and dignity; and that if beauty be t determined by suffrages, the elliptical arch have little to boast, since the only bridge of kind has now stood two hundred years without tation.

If in opposition to these arguments, and in fiance at once of right reason and general author

Circular arch th the ellip to a strait vhose dimi

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ny mass 18
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will the world believe, than that some other motive than reason influenced the determination? And some degree of partiality cannot but be suspected by him, who has been told that one of the judges appointed to decide this question, is Mr M-II-r, who having, by ignorance or thoughtlessness, 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-ps-n declares it to be false.

more

He that in the list of the committee chosen for the superintendency of the bridge, reads many of the most illustrious names of this great city, will hope that the greater number will have reverence for the opinion of posterity, than to disgrace themselves, and the metropolis of the kingdom, in compliance with any man, who, instead of voting, aspires to dictate, perhaps without any claim to such superiority, either by greatness of birth, dignity of employment, extent of knowledge, or largeness of fortune.

jection

bserve,

SIR,

LETTER II.

Dec. 8. 1759.

IN questions of general concern, there is no law
of government, or rule of decency, that forbids
open examination and publick discussion.
shall therefore not betray, by a mean apology, that

I