* * * * * A primary inquiry, in regard to Towers in an exposed situation, is the question, whether their stability should depend upon their _strength_ or their _weight_; or, in other words, on their _cohesion_, or their _inertia_? In preferring _weight_ to _strength_, we more closely follow the course pointed out by the analogy of nature; and this must not be regarded as a mere notional advantage, for the more close the analogy between nature and our works, the less difficulty we shall experience in passing from nature to art, and the more directly will our observations on natural phenomena bear upon the artificial project. If, for example, we make a series of observations on the force of the sea, as exerted on masses of rock, and endeavour to draw from these observations some conclusions as to the amount and direction of that force, as exhibited by the masses of rock which resist it successfully and the forms which these masses assume, we shall pass naturally to the determination of the _mass_ and _form_ of a building which may be capable of opposing similar forces, as we conclude, with some reason, that the mass and form of the natural rock are exponents of the amount and direction of the forces they have so long continued to resist. It will readily be perceived, that we are in a very different and less advantageous position when we attempt, from such observations of natural phenomena, in which _weight_ is solely concerned, to deduce the _strength_ of an artificial fabric capable of resisting the same forces; for we must at once pass from one category to another, and endeavour to determine the _strength_ of a comparatively _light_ object which shall be able to sustain the same shock, which we know, by direct experience, may be resisted by a given _weight_. Another very obvious reason why we should prefer _mass_ and _weight_ to _strength_, as a source of stability, is, that the effect of mere _inertia_ is constant and unchangeable in its nature; while the _strength_ which results, even from the most judiciously disposed and well executed fixtures of a comparatively light fabric, is constantly subject to be impaired by the loosening of such fixtures, occasioned by the almost incessant tremor to which structures of this kind must be subject, from the beating of the waves.[7] Mass, therefore, seems to be a source of stability, the effect of which is at once apprehended by the mind, as more in harmony with the conservative principles of nature, and unquestionably less liable to be deteriorated than the _strength_, which depends upon the careful proportion and adjustment of parts.