Preface.

...writing a book for the learned—or for those who can help themselves through other necessary sciences, or even enjoy instruction and explanation from others—is a very different matter than writing for someone who entirely lacks such advantages and instruction and must rely solely on his own reflection and the book itself.

Fourthly, it should not be considered an oversight that for many machines no scale Maaßstab: a ruler or scale bar used to indicate physical dimensions is noted, neither on the drawing nor in the writing. This is because these are mostly examples intended only for explanation, not for direct imitation. Or, they are machines that suffer constant change due to materials, time, location, force, load, or other circumstances, and it is sufficient if the mechanical proportions original: "mechanischen Verhältnisse" are simply expressed.

Fifthly, the fact that various machines are not fully depicted with all their accessories, housings, stands, or even other necessary pieces, has occurred in those instances where one only wished to show certain proportions; the complete description of these remains set aside for another part of the Theater original: "Theatri".

Sixthly, it is to be remembered that here, not only are the so-called five powers Potentien: the five "simple machines" of classical mechanics—the lever, pulley, wheel and axle, inclined plane, and screw or simple lifting-tools original: "Heb-Zeuge" (which are otherwise treated as the sole principles of mechanics original: "Principia mechanica") presented in figures and explained through special machines; but also the external forces—such as those of animals, water, fire, air, and weights—have been detailed as much as current possibilities allow. This includes their properties and how they may be applied to machines with advantage and utility. This is a matter that is highly indispensable and almost more necessary than the first, yet until now has been described by few or not at all—especially regarding how such forces are to be used with the best advantage in mechanics. And this is primarily because it is a matter that must be investigated more through experience and experiments original: "Experimente" than through mere speculation original: "Speculationes" on paper. Such investigation requires much time, expense, experiments, machines, and above all, convenient opportunity—things which the author original: "Autori" has lacked in many respects until now. Therefore, several things must remain undecided for the time being; however, this has been noted each time and some guidance given. There is no doubt that many a person who possesses these aforementioned requirements might, out of love for the art and the advancement of the Fatherland, not refrain from making such experiments and be pleased to kindly communicate them for the benefit of the public.