It has yet been sometimes asserted by hardy ignorance, that the elliptical arch is stronger than the semicircular; or in other terms, that any mass is more strongly supported the less it rests upon the supporters.  If the elliptical arch be equally strong with the semicircular; that is, if an arch, by approaching to a straight line, loses none of its stability, it will follow, that all arcuation is useless, and that the bridge may at last, without any inconvenience, consist of stone laid in straight lines from pillar to pillar.  But if a straight line will bear no weight, which is evident at the first view, it is plain, likewise, that an ellipsis will bear very little; and that, as the arch is more curved, its strength is increased.

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

If, in opposition to these arguments, and in defiance, at once, of right reason and general authority, the elliptical arch should at last be chosen, what 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—­ll—­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.

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 more 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.

LETTER II.

SIR, 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.  I shall, therefore, not betray, by a mean apology, that right which no man has power, and, I suppose, no wise man has desire to refuse me; but shall consider the letter published by you last Friday, in defence of Mr. M——­’s[1] design for a new bridge.

Mr. M——­ proposes elliptical arches.  It has been objected, that elliptical arches are weak; and, therefore, improper for a bridge of commerce, in a country where greater weights are ordinarily carried by land, than, perhaps, in any other part of the world.  That there is an elliptical bridge at Florence is allowed, but the objectors maintain, that its stability is so much doubted, that carts are not permitted to pass over it.