“Amber has a fatty and glutinous humor which, being emitted, the dry object desiring to absorb it is moved toward the source, that is the amber. For every dry thing, as soon as it begins to absorb moisture, is moved toward the moist source, like fire to its pasture; and since the amber is strongly rubbed, it draws the more because of its heat.”

— Gerolamo Cardano (1550), On the Subtlety of Things (Volume 5) [10]

“Hero's engine (150 BC) was a form of reaction turbine; Gerbert, a professor in the schools of Rheims (1125), had an ‘organ worked by heated water’; Leonardo da Vinci (about 1500) proposed a steam gun; Cardan (about 1550) devised a machine using the vacuum from condensed steam; Porta (Naples, 1601) raised water by steam pressure, also using the vacuum idea; and de Caus (France, about 1600) forced water up by a steam fountain’. A different type of machine (corresponding to the impulse turbine) was the steam ‘hurdy-gurdy’ of Branca, in Italy, in 1629. All of the foregoing types may be said to be experimental or preparatory to the period which followed. The first machine which did actual work was that of Edward Somerset, Marquis of Worcester, in about 1663. We next hear of an alcohol engine, using a surface condenser, proposed by Hautefeuille (1678). This appears to have been forgotten. In 1690 the Frenchman Papin devised the first engine with a piston, and in 1698 Thomas Savery patented an apparatus for lifting water from the Cornish mines. Two vessels were filled with steam alternately, the maximum lift being 24 feet. This type is still in use; it is known as the "pulsometer." It may be of interest to note that the story of the "boy and the teakettle" is told of Worcester, of Savery, and of Watt. Thomas Newcomen in 1705 produced a machine where a jet of water was thrown into the cylinder. In all these engines, the valves were worked by hand. Now we come to the story of Humphrey Potter, the boy who in 1713 devised a self-acting valve motion which he called a "scrogger." With practically no other improvement, the steam engine remained as it was for about forty years. James Watt in 1763 was repairing a model of an engine (Newcomen type) from a collection in a college in Glasgow. In 1765 the idea of the separate condenser struck him, and he then began his great work. Though sometimes discouraged and reduced to poverty, forced to discontinue his experiments and go to work at surveying for support, he persevered; and the next ten years saw the addition of the governor, expansive working, the indicator, the principle of compounding, etc. He found the steam engine a crude and imperfect apparatus, and left it a marvelous instrument for the progress of the world.”

— A.L. Jordan (1917), “Short Stories of Great Inventions” [5]

“Both Cardan and Porta were concerned with the phenomena of steam, but though they made some progress their results were seriously qualified by misconceptions of the nature of steam, which they still identified with air. Cardan in one obscure passage (1550) points out that a vacuum may be created by the condensation of steam; this suggestion, cogent as it would have been if clearly conceived, can hardly have had the significance that we might naturally be inclined to attribute to it. Porta's work on steam was rather more deliberate, and some of his experimental apparatus was highly suggestive. The attempt to measure the volume of steam by the amount of water displaced by steam pressure led him close to a positive distinction between steam and air, but he drew no decisive conclusions him-self. A late contemporary, Salomon de Caus, with essentially similar apparatus, took this decisive step. He declared that steam is evaporated water, and that upon cooling the vapor returns to its original condition. A similar experiment with mercury showed the same phenomena of evaporation and subsequent return to the liquid condition. De Caus was thus able to set down (1615) a series of propositions that represented a great advance upon all previous achievements in the field of gases and their phenomena. Air and steam were thus specifically distinguished and the practical conclusion was drawn that there were potentialities in steam pressure of much greater magnitude than were to be found in air pressure.”

— Abbott Usher (1929), A History of Mechanical Inventions [4]

“The text of the passage of Cardan to which Usher refers contains, first, the emphatic and categorical statement that a vacuum does not exist; and, secondly, the statement that if you assume, for the sake of argument, that a vacuum does exist, you cannot explain anything by it. The argument is, first, that we have no evidence of the existence of the vacuum; and, secondly, that the assumption of a vacuum explains nothing. Cardan’s point of view is here best presented in his own alternative theory that the effects hitherto ascribed to a vacuum are really effects brought about by unnatural rarity of a substance.”

— Myrtle Cass (1934), “commentary on Cardan’s De Subtilitate” [7]

“European scholars in 1500, still held to the Greek view which did not distinguish steam from air. The vacuum was not understood; it was still something ‘abhorred by nature’. Girolamo Cardan suggested that a vacuum might be produced by the condensation of steam. Giovanni Porta, an Italian philosopher, came close to distinguishing steam from air, but did not make the conception explicit. It was Salomon de Caus, a French landscape gardener and engineer, who ‘took this decisive step’, according to Usher (1929): he declared that steam is evaporated water; that upon cooling the vapor ‘returns to its original condition’.”

— Leslie White (1975), Modern Capitalist Culture [2]

“The first book of Cardano's De subtilitate (1550) was devoted to the general principles of ‘matter, form, vacuum, the repulsion of bodies, natural motion, and place’; his discussion of the various devices that some claim prove the existence of the vacuum are derived in part from Valla. But Cardano must have had a source beyond Valla, since he described a machine that Valla had omitted (Pneumatica 1.37). Elio Nenci, Cardano's modern editor, suggested that he also relied on the preliminary discussion of the vacuum omitted by Valla, but I see no evidence of that—Cardano never mentions the interparticulate vacuum, for instance.”

— Roy Laird (2017), “Hero of Alexandria and Renaissance Mechanics” [8]

“Internal evidence, together with the actual history of the manuscripts, have made it clear that they were circulated rather extensively. The entire mass of manuscripts was left to the care of Francisco Melzi, the secretary and friend of Leonardo. In order to enhance the fame of his master, Melzi permitted copies to be made of various manuscripts and, with some restrictions, allowed various artists and scientists to use the collection. After Melzi's death his heirs were less concerned about the preservation of the collection intact. Some volumes were sold, some were given away, some were stolen. Leonardo's work was thus of direct influence for not less than two generations. Among the scientists allowed to delve in this fertile source of inspiration was Jerome Cardan, a Milanese of genuine talent and of a rather acquisitive disposition. Most of the theories of Leonardo in the field of mechanical sciences thus appeared in print in an organized form in the two substantial treatises of Cardan: De subtilitate (The Fineness) and Opus novum de proportionibus (We Need a New Proportions). It was in this form that the work of Leonardo came to exercise its most notable influence upon the early development of the mechanical sciences.

The most decisive innovation was the introduction of systematic experimentation. This mode of inquiry is in evidence at every turn, sometimes incidentally, sometimes as a protracted search for specific formulas. The phenomena of percussion and recoil were studied. Experiments were made with falling bodies and a formula for the acceleration was suggested. The strength of struts and girders was studied with reference to variations of length and cross section; differences between single members and composite members were also determined. It is not easy to separate the new from the old, but nearly all this work was new in spirit, and even if not immediately final it was by these methods that final results were achieved.

Dynamics received much attention, but the results were not decisive. The old metaphysical impediments to the effective study of motion were overcome and most of the fundamental problems were studied. Leonardo's mind was reaching out to a new concept of force, and though his formulation was not wholly happy it contained important elements of truth. He made it easier to proceed with the study of the flight of projectiles, impacts, and falling bodies, though he himself achieved no final results. He was progressing toward a formulation of the principles of the composition of forces, but there is much doubt as to the exact nature of his accomplishment. There is always a danger of our reading later knowledge into his notes and diagrams. In this whole field one fact is patent: all the important problems were redefined by Leonardo's efforts, and reduced to forms that made solution possible. This in itself is no mean achievement. As the solutions of the primary problems of principle were not achieved until rather more than a century later, we may readily judge the difficulties that remained. Leonardo defined problems of dynamics that were adequately solved only through the efforts of Galileo and Huygens.

In the field of statics, the achievements of Leonardo were less novel but more complete and finished. All the primary problems and concepts were derived from the medieval writers, most especially from the ‘school of Jordanus’ and the work of Albert the Saxon [c.1320-1390] (Ѻ)(Ѻ)(Ѻ)(Ѻ). Under his hands, the rather imperfectly apprehended principles became a system of thought which carried Leonardo far. The work of the school of Jordanus was developed until all the primary theorems were clearly enunciated and the scope of mathematical calculation in mechanics greatly extended. The propositions and corollaries of Albert the Saxon were elaborated, and a correct solution was given for the equilibrium of a body. As long as the center of gravity is above the base of a body, the body remains in equilibrium; otherwise it falls. The doctrine of the center of gravity had thus carried Leonardo definitely into the boundaries between statics and dynamics. Furthermore, speculation along the lines of these problems and principles led him to adopt the heliocentric hypothesis as early as 1508. This is significant only as an index of the intellectual temper of Italy at that time, for Copernicus had already begun work upon the problem, largely as a result of the stimulus of contacts with Italy.”

“As for the opinions of Epigenes, Bienewitz, Cardano, Scaliger, let these pass because they are not apposite to the subject and I do not have the at hand right now a copy of their work. As for whether storms are stirred by demons, as Paracelsus holds, this should be discussed at some length and a distinction should be made between the demons.”

— Otto Guericke (1665), “Reply Letter to Sanislaus Lubienietzki”, Mar 29; in New Experiments on the Vacuum of Space (pg. 289)