The place of Leonardo in history as an artist and even as a scientist is well known. Many of his inventions, such as the helicopter, were only on paper, however. His actual achievements and contributions to the technology of his time are less well known and somewhat problematical. On the one hand, it is said that none of his ideas were practical, while on the other, it is said that his improvements in canal locks have been imitated ever since. After striking success as a painter in his youth, Leonardo, at about age 30, began to take commissions in fields that we would today identify as architecture or engineering.

From then on, he made at least part of his living designing improvements on buildings and canals, some of which he then built and some of which languished. Increasingly he designed in secret devices that anticipated flight, steam power, and much more. Much of the reason for the apparent mystery of his ideas about technology is that he wrote and drew them in coded notebooks that, although he worked on them for much of his adult life, were never sufficiently organized to decode and publish. Indeed, most pages of the notebooks were not published until late in the 19th century. All his life he found it difficult to complete a task, even abandoning paintings for which he had been paid. Single pages of the famous notebooks, although nearly all written so that each deals with a separate chain of thought, often slip from one topic to another. Among the public achievements that contributed to the technology of his time are the maps of Italy he made at the beginning of the 16th century.

Although none of his architectural plans were executed, many were known at the time and became a major influence on such buildings as St. Peter’s in Rome. In addition to canal lock gates, replacements in 1497 for worn-out gates on the oldest canal in Italy, it is thought that he actually built a screw-cutting machine and a turret windmill, both advanced for the time and not followed by others until much later. Some give Leonardo partial credit (along with Palladio) for the truss bridge, but trusses were occasionally used by the Romans and did not become common in bridges until centuries after Leonardo’s death. It is thought that some may have seen his notebooks and been influenced, notably Girolamo Cardano, but that is not certain. If they had been, we might have earlier had the advantage of Leonardo’s experiments with tensile strength, his analysis of forces produced by arches and hoisting devices, and his work on the strength of beams and columns.

A half century after Leonardo’s death, another great Italian, Galileo, repeated such experiments and analyses –– and published them in a clear, coherent form.