Economy denotes the the proper management of materials and of site, as well as a thrifty balancing of cost and common sense in the construction of works. ...the architect does not demand things which cannot be found or made ready without great expense. For example: it is not everywhere that there is plenty of pitsand, rubble, fir, clear fir, and marble... Where there is no pitsand, we must use the kinds washed up by rivers or by the sea... and other problems we must solve in similar ways.

Geometry is of much assistance in architecture, and in particular it teaches us the use of the rule and compasses, by which especially we acquire readiness in making plans for buildings in their grounds, and rightly apply the square, the level, and the plummet. By means of optics the light in buildings can be drawn from fixed quarters of the sky. Difficult questions involving symmetry are solved by means of geometrical theories and methods.

For not all things are practicable on identical principles

The winter oak... is very useful in buildings but when in a moist place it takes in water to its centre... and so it rots. The Turkey oak and the beech both... take in moisture to their centre and soon decay. White and black poplar, as well as willow, linden, and the agnus castus... are of great service from their stiffness... they are a convenient material to use in carving.

The oak has not the efficacy of the fir, nor the cypress that of the elm.

Now architecture consists of order, which in Greek is called taxis ... Order is the balanced adjustment of the details of the work separately, and, as to the whole, the arrangement of the proportion with a view to a symmetrical result.

In the midst of all this great variety of subjects, an individual cannot attain to perfection in each, because it is scarcely in his power to take in and comprehend the general theories of them.