Sources: Galileo's Correspondence

Sources: Galileo’s Correspondence Notes on the Translations The following collection of letters is the result of a selection made by the author from the correspondence of Galileo published by Antonio Favaro in his Le opere di Galileo Galilei,theEdizione Nazionale (EN), the second edition of which was published in 1968. These letters have been selected for their relevance to the inves- tigation of Galileo’s practical activities.1 The information they contain, moreover, often refers to subjects that are completely absent in Galileo’s publications. All of the letters selected are quoted in the work. The passages of the letters, which are quoted in the work, are set in italics here. Given the particular relevance of these letters, they have been translated into English for the first time by the author. This will provide the international reader with the opportunity to achieve a deeper comprehension of the work on the basis of the sources. The translation in itself, however, does not aim to produce a text that is easily read by a modern reader. The aim is to present an understandable English text that remains as close as possible to the original. The hope is that the evident disadvantage of having, for example, long and involute sentences using obsolete words is compensated by the fact that this sort of translation reduces to a minimum the integration of the interpretation of the translator into the English text. 1Another series of letters selected from Galileo’s correspondence and relevant to Galileo’s practical activities and, in particular, as a bell caster is published appended to Valleriani (2008). M. Valleriani, Galileo Engineer, Boston Studies in the Philosophy of Science 269, 213 DOI 10.1007/978-90-481-8645-7, C Springer Science+Business Media B.V. 2010 214 Sources: Galileo’s Correspondence Galileo to G. Contarini in Venice. Padova, March 22, 15932 Most Illustrious Lord, I heard from the Illustrious Lord Gianvincenzo Pinelli the problem of Your Most Illustrious Lordship, about which I will tell you what I believe is true: and it is this. Concerning the need to apply more or less force in propelling the vessel forward, it does not make any difference if the oar lies on the live or dead part of the deck, since all other circumstances are the same. And the reason is that, since the oar is practically a lever, as long as force, support and resistance divide it with the same proportion, it will operate with the same vigor, and this is a universal and invariable proposition. And I do not believe that making the wings in the galley will achieve anything but the ease of having more space for the soldiers and convicts, who otherwise could not be seated in rows of four or five per oar, especially toward stern and bow, if there were no wings. But if they could sit and row both in one way and in the other way, I do not necessarily believe that placing the protection inside or outside the live part of the galley would make any difference if, however, the oar is divided with the same proportion. And I do not see anything that could hinder or facilitate the rowing other than placing the protection further away from or closer to the handle: the closer it is, the more one can apply force. And the reason is the following, a reason that has perhaps not been investigated by anyone else: The oar is not a simple lever like any other one, indeed, there is a great difference for the following reason. Ordinarily the lever should have a mobile force and a mobile resistance and a support at rest, but in a galley support, force and resistance move. It follows from this that support and resistance are the same because when the blade of the oar is placed in the water, the water becomes the support, and the protection becomes resistance. But when the oar moves the water, in this case it becomes the resistance, and the protection is the support. And since, when the support is fixed, the whole force is applied to move the resistance, if the oar is immersed so that the water becomes almost immovable, then most of the force is employed to propel the vessel. On the contrary, if the oar is immersed so that the water is moved easily by the blade, then one is not able to apply the force to move the boat. And since the greater the length of the part of the lever is toward the force, the more easily one can move the resistance, when the part of the handle is very long, the water will be moved more easily, and hence its support will be weaker and one will propel the vessel less. On the contrary, when the same part between the protection and the force is shorter, then it will be more difficult to move the water with the blade and consequently, since it is needed as support, it is more solid and one is able to propel the vessel with more force. And one concludes that, the closer the protections are to the handle, the stronger the force can be applied in propelling the vessel, as the water is not able to be moved so easily with a blade very distant from the protection by a force close to the same protection. Hence, in such a case, the water functions 2EN, X:55–57. Galileo to G. Contarini in Venice. Padova, March 22, 1593 215 more as support than resistance. All of this is very evident from experience. Hence, since only the larger or smaller distance between the protection and the force can give ease or discomfort to the stroke, I absolutely do not believe that placing the protection on the live or dead part of the deck makes any difference. This is what occurs to me up to now in answer to your doubts and I believe that Your Most Illustrious Lordship has spoken more clearly about this. But if you would like to share your thoughts on this business with me, I would remain infinitely obligated to you since I am sure I would learn much and perhaps your arguments would induce some other things to occur to me. I beg you that when similar problems are in the air, you condescend to share them with me, since I take great pleasure in thinking of curious things. I sent the letter of Your Most Illustrious Lordship to my friend the sculptor but have not yet received an answer. With this, I bow very modestly to you and beg you to summon me. From Padova, March 22, 1593. Very Obligated Servant of Your Most Illustrious Lordship Galileo Galilei Addressed to: Most Illustrious Lord and My Very Cultivated Master Lord Iacomo Contarino Venice 216 Sources: Galileo’s Correspondence G. Contarini to Galileo in Padova. Venice, March 28, 15933 My Most Magnificent and Excellent Lord, To my great pleasure I saw what Your Most Excellent Lordship wrote to me in reference to the oars of the galleys. Although I do not have much time, since you ask me to write to you about some of the things related to this business that are on my mind, I tell you that, for the observations I did, the oars normally used are not proportional to the body of the vessel. But one should put some thought into proportioning these two things together so as to obtain what is required, that is, agility and velocity. And in my opinion one can obtain the mentioned proportion from three things: from the width of the live body of the vessel, from the height between the water and the position of the oar, and from the motion that the galley- slave communicates [to the oar] while pulling it. Speaking first about the last issue, which is the moving force, I say that when the galley-slave begins to row, one should consider that he is obliged to perform one of three motions: either to pull the oar from the bottom upwards, since it is low; or from the top downwards, since it is high; or straight to the breast, since it is placed between these two extremities. Now one can understand very well that those two above-mentioned extreme movements, being violent, tend to lack force and are very difficult to endure. Thus, one should place the oar in such a way that, by pulling it, it comes to the chest when the man is standing with the advantage that, when the galley-slave loses his balance due to the weight of his body, he moves the oar more easily than when just using ordinary force. In supposing this, which is not difficult, it is necessary to understand what is the right position and the right height to position the oar in reference to the protection above water-level. And one can find this easily if the height of the man who rows and the length of the oar are considered. Thus, the oar should be placed at a height where it can touch the water without the galley-slave performing one of the two extreme movements mentioned above. To do this, the oar should be long and touch the water at a great distance from the ship so that the galley-slave does not have to row with raised arms. But another need arises because, having a long oar, a greater force is needed to move it, to row with it, as well as to raise and to lower it.

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