|The main parts of the Galileo engine (1632), shown without weight bucket attacked (to hook k), comprised of cylinder ABCD, inserted with piston EFGH, and adjustable wire/hook device IK, with conical head I, which can allow the excess fluids to escape, prior to fitting the conical head into its groove, which Galileo proposes can be used to test the "force of the vacuum". |
In 1632, Galileo (EP:10), in his Dialogues Concerning the Two New Sciences, following preliminary dialogue of the possiblity of "vacuum breaking", presented a dialogue on the possibly of vacuum formation or rather the "resistance of the vacuum" made by nature, being that he believed that vacuums could not exist, per the nature abhors a vacuum dictum, in siphon water pumps that stopped working past about 30-feet.
The following is an important preliminary or pre-context statement by Galileo (voice: Salviati):
“I feel that for a complete explanation, of the question of what is binding material which holds together the parts of solids so that they can scarcely be separated, other considerations might well enter; yet I must not now digress upon this ‘particular topic’ since you are waiting to hear what I think about the breaking strength of other materials which, unlike ropes and most woods, do not show a filamentous structure. The coherence of these bodies is, in my estimation, produced by other causes which may be grouped under two heads. One is that much-talked-of repugnance which nature exhibits towards a vacuum; but this ‘horror of a vacuum’ NOT being sufficient, it is necessary to introduce another cause in the form of a gluey or viscous substance which binds firmly together the component parts of the body. First, I shall speak of the vacuum, demonstrating by definite experiment the quality and quantity of its force [virtù]. If you take two highly polished and smooth plates of marble, metal, or glass and place them face to face, one will slide over the other with the greatest ease, showing conclusively that there is nothing of a viscous nature between them. But when you attempt to separate them and keep them at a constant distance apart, you find the plates exhibit such a repugnance to separation that the upper one will carry the lower one with it and keep it lifted indefinitely, even when the latter is big and heavy.”— Galileo (1638), Dialogues Concerning the Two New Sciences (pgs. 8 + 11)
The main dialogue, in regards to Galileo's "vacuum measuring" device, pictured adjacent, is as follows:
Sagredo [Baliani]: “go ahead, Salviati; assume that I admit your conclusion and show us your method of separating the action of the vacuum from other causes; and by measuring it show us how it is not sufficient to produce the effect in question.”
Salviati [Galileo]: “I will tell you how to separate the force of the vacuum from the others, and afterwards how to measure it. For this purpose let us consider a continuous substance whose parts lack all resistance to separation except that derived from a vacuum, such as is the case with water, a fact fully demonstrated by our Academician in one of his treatises. Whenever a cylinder of water is subjected to a pull and offers a resistance to the separation of its parts this can be attributed to no other cause than the resistance of the vacuum. In order to try such an experiment, I have invented a device [engine], shown below, which I can better explain by means of a sketch than by mere words.Let CABD represent the cross section of a cylinder either of metal or, preferably, of glass, hollow inside and accurately turned. Into this is introduced a perfectly fitting D cylinder of wood, represented in cross section by EGHF [piston], and capable of up-and-down motion [see: reciprocating motion]. Through the middle of this cylinder is bored a hole to receive an iron wire, carrying a hook at the end K, while the upper end of the wire, I, is provided with a conical head. The wooden cylinder is countersunk at the top so as to receive, with a perfect fit, the conical head I of the wire, IK, when pulled down by the end K. Now insert the wooden cylinder EH in the hollow cylinder AD, so as not to touch the upper end of the latter but to leave free a space of two or three finger-breadths; this space is to be filled with water by holding the vessel with the mouth CD upwards, pushing down on the stopper EH, and at the same time keeping the conical head of the wire, I, away from the hollow portion of the wooden cylinder. The air is thus allowed to escape alongside the iron wire (which does not make a close fit) as soon as one presses down on the wooden stopper.
The air having been allowed to escape and the iron wire having been drawn back so that it fits snugly against the conical depression in the wood, invert the vessel, bringing it mouth downwards, and hang on the hook K a vessel which can be filled with sand or any heavy material in quantity [weight] sufficient to finally separate the upper surface of the stopper, EF, from the lower surface of the water to which it was attached only by the resistance of the vacuum. Next weigh the stopper and wire together with the attached vessel and its contents; we shall then have the force of the vacuum [forza del vacuo]. If one attaches to a cylinder of marble or glass a weight which, together with the weight of the marble or glass itself, is just equal to the sum of the weights before mentioned, and if breaking occurs we shall then be justified in saying that the vacuum alone holds the parts of the marble and glass together; but if this weight does not suffice and if breaking occurs only after adding, say, four times this weight, we shall then be compelled to say that the vacuum furnishes only one fifth of the total resistance [resistenza].”
In c.1645, this Galileo theoretical engine, in the mind of Otto Guericke, inspired the construction of the Guericke engine, which inspired the pneumatical engine (1658) device of Robert Boyle and Robert Hooke, along with the gunpowder engine devices and later steam engine devices of Christiaan Huygens and Denis Papin.
1. (a) Galilei, Galileo. (1638). Discourse and Mathematical Demonstration of the Two New Sciences (Discorsi e dimostrazioni Matematiche Intorno a Due Nuove Scienze) (pg. 15). Leiden.
(b) Boschiero, Luciano. (2007). Experimental and Natural Philosophy in Seventeenth-century Tuscany (pg. 118). Springer.
(c) Galileo. (1632). Dialogues Concerning the Two New Sciences (translators: Henry Crew and Alfonso Salvio) (Lagrange quote, pg. v; stone column, pg. 7; engine, pg. 14). Macmillan, 1914.