THE GREAT ART

OF ARTILLERY

PART ONE

BOOK I.

ON THE CALIBER RULE.

Large decorative initial P at the beginning of the main text, containing floral and vine-like ornamentation within a square border.

The first and principal instrument of the pyrotechnicians, which we call the REGVLA CALIBRÆ Caliber Rule—a term used by all Spanish, French, and Italian pyrotechnicians—is called Mas-stab or Visier-stab by the Germans, and Tal-stock by the Dutch. In the Latin idiom, we shall not improperly call it the Virga seu Regula Sphaeometrica Sphæometric rod or rule. By these aforementioned terms, we mean nothing else than a certain rule in the shape of a rectangular prism, longer on one side, or a truncated solid quadrangular pyramid, constructed from some metal that is not easily flexible, or from a harder wood. On one flat surface of this (as is commonly done), a straight line is drawn, divided into unequal parts according to a stereometric or cubic ratio, adapted for examining the weights of iron globes through their diameters. Therefore, from the diameter of a one-pound (or even one-loton) globe, it has the diameters of other globes of the same metal marked out to infinity, or rather, as far as the length of the line permits. On the second and third surfaces of the same rule, lines are likewise described in a similar manner, divided according to the diameters of lead and stone globes of varying weights, following in natural order and sequence, dedicated to examining the weights of globes fashioned from these metals as well. Finally, the fourth and last surface of the same rule shows the measure of one Rhenish or, as many prefer, Roman foot, divided into twelve inches or larger digits. With this measure, one may measure all pyrotechnic bodies as well as flat surfaces and lines. But now the matter itself demands that, having described the REGVLA CALIBRÆ instrument, we show its various methods of construction, as well as its primary use in artillery, and that we do so in the following order and method.