PREFACE.

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...help than that which they have drawn from the reflections suggested to them by long experience; for one must admit that there are Practitioners original: "Praticiens"; skilled builders or craftsmen who rely on hands-on experience rather than formal academic training. who find marvelous resources within the superiority of their genius, and that in general, it is to persons of this character that we are indebted for the most happily imagined inventions in the Arts original: "Arts"; here referring to the mechanical and technical trades rather than fine arts..

But one must take care: when one is capable of meditating upon a project and of holding one's attention for a long time on a single thing in order to develop all its facets—so as to decide only in favor of the most advantageous choice—this manner of thinking is a true theory original: "théorie"; here used to mean a systematic mental framework or the underlying logic of a design. to which the subsequent success is owed. In such cases, without knowing it, one imitates Geometers original: "Géométres"; in the 18th century, this term was synonymous with mathematicians and physical scientists.; one possesses their spirit and their outlook, since one seeks to reach the same goal. The only difference is that the former arrive there without going astray, via a path whose progress they understand, while the others, deprived of the lights that might guide them, are exposed to many missteps.

When it is necessary to measure forces exactly, where the directions, levers original: "leviers", and supports original: "appuis"; refers to fulcrums or structural points of resistance. are not readily apparent, these are always very difficult investigations. Cases often arise where the forces original: "puiſſances"; in 18th-century mechanics, this refers to the active powers, loads, or energy acting on a machine or structure. whose action must be considered involve such complicated ratios that it is impossible to perceive them without the help of a very refined theory, which cannot be attained unless one is prepared with a great deal of knowledge acquired through continuous study.

There are things essential to know that experience original: "expérience"; practical observation and hands-on trial-and-error. never teaches, and which one cannot be ignorant of if one wishes to see clearly what one is doing. I refer to the good faith of those who have overseen work for a long time; there are none among them who have not felt, on a thousand occasions, that they lacked certain principles original: "principes"; fundamental laws of physics and mathematics. in which they would have wished to be instructed. Most have entered upon a career that was not...