PROGRESS OF THE ARTS. 369 



find, in the best works of the architects of all ages 

 (including engineers), evidence that the true idea 

 of mechanical pressure exists among them more 

 distinctly than among men in general, although it 

 may not be developed in a scientific form. This 

 is true up to our own time, and the arts which 

 such persons cultivate could not be successfully 

 exercised if it were not so. Hence the writings 

 of architects and engineers during the middle ages 

 do really form a prelude to the works on scientific 

 mechanics. Vitruvius, in his Architecture, and 

 Julius Frontinus, who, under Vespasian, wrote On 

 Aqueducts, of which he was superintendent, have 

 transmitted to us the principal part of what we 

 know respecting the practical mechanics and hy- 

 draulics of the Romans. In modern times the 

 series is resumed. The early writers on architec- 

 ture are also writers on engineering, and often on 

 hydrostatics: for example, Leonardo da Vinci wrote 

 on the equilibrium of water. And thus we are 

 led up to Stevinus of Bruges, who was engineer 

 to Prince Maurice of Nassau, and inspector of the 

 dykes in Holland ; and in whose work, on the 

 processes of his art, is contained the first clear 

 modern statement of the scientific principles of 

 hydrostatics. 



Having thus explained both the obstacles and 

 the prospects which the middle ages offered to the 

 progress of science, I now proceed to the history of 

 the progress, when it was once again resumed. 

 VOL. i. BB 



