China
Africa
Explore chapters and articles related to this topic
Portuguese Claims to the Exclusive Domination of the Indian Ocean Regions
Published in K.S. Mathew, Shipbuilding, Navigation and the Portuguese in Pre-modern India, 2017
Cross staff was used for altitude-measuring for navigation and came into use in the sixteenth century. Even if this was already in existence and was probably invented by Judaeo-Provençal philosopher and scientist Levi ben Gerson (1288–1344), its use became popular in the sixteenth century only. The Jew described it in his treatise in 1342. There is no evidence to affirm that The Cross Staff was used for navigation before the sixteenth century. It was João de Lisboa and André Pires writing in 1520 who made reference to it for the first time for navigation.18 The cross staff used in navigation differed slightly from the cross staff described by the Catalan Jew by name Levi ben Gerson. The one employed for navigation had a scale which gave readings in degrees, and it is the origin of this form which is of particular interest in the history of navigation. The earliest surviving nautical cross-staff is probably the wooden instrument left by Jacob van Heemskirck and Willen Barenstszoon in the ‘Behouden Huis’ at Nova Zembla in 1596 or 1597. It has been suggested that the navigator’s interest in the cross-staff was aroused by acquaintance with the Islamic kamal (also known as the tavoletas da India mentioned both by João de Lisboa and André Pires).19
Transportation
Published in Jill L. Baker, Technology of the Ancient Near East, 2018
To successfully navigate the seas, sailors utilized several tools: a lead line, timekeeping, a cross-staff, an astrolabe, and the stars. The lead line was a long rope attached to a weight with knots at regular intervals (Herodotus Histories, 2.5; Strassler and Purvis 2007:118–119). By lowering the line, sailors knew the depth of the water at the given position, which helped them determine their position on the sea. The Egyptians used this device at around 3400 bce, and it remained in use into the Greek period, as mentioned by Herodotus. In 1600 ce, the English continued its use marking out the fathoms at regular intervals. By keeping track of time onboard ship, the sailors could estimate the position of the sun relevant to their position, and determine how long and far they traveled by keeping track of their speed. To aid in all this, sailors used several sand glasses, known to us as an hourglass. A cross-staff dates to ca. 400 bce and was a long cross bar with a shorter cross bar attached at a right angle in the middle of the longer one. The long part of the cross-staff was placed below the user’s eye with the other end pointed toward the sun or Polaris so that the observer could position the upper end of the crossbar to the sun or Polaris and the horizon. The crossbar became the transom, and the long end the staff. Once the sun/Polaris and the horizon were aligned with the cross-staff, one’s angular altitude could be calculated. An astrolabe, Greek for “star taker,” was an inclinometer, which was used to locate and predict the positions of celestial bodies, calculate a local time at a given latitude, and was used in surveying and triangulation. This device is considered to have been a Hellenistic invention by Apollonius of Perga or Hipparcus around ca. 220 bce/150 bce. It was originally used in astronomy and astrology and adapted for maritime navigation. Finally, the stars and planets themselves provided navigational aid to sailors. The Phoenicians kept land in sight while also keeping track of the stars, specifically Polaris, the North Star, also called the Phoenician Star (see Mariners Weather Log, www.vos.noaa.gov/MWL/aug_08/navigation_tools.shtml).
Instruments of statecraft: Humphrey Cole, Elizabethan economic policy and the rise of practical mathematics
Published in Annals of Science, 2018
The next important English source for the cross-staff is not a published book, but a list of instruments purchased by Captain Frobisher’s for his first (1576) voyage in search of the North-West passage. These were made by Humphrey Cole, and alongside ‘a great globe of metal’, sundials, magnetic compasses etc. we find ‘an instrument made of wood a stafe named Balestetta [sic]’, bought for 13s 4d.73 And in an early account of Frobisher’s voyages, the author, George Best, claims that instruments of Astronomie to take Longitudes and Latitudes of Countreys, and many other helps, are so commonly knowen to euery Mariner nowadays, that he that hath bin twice at Sea, is ashamed to come home, if he be not able to render accompte of all these particularities74By the end of the sixteenth century the cross-staff was widely used in navigation, and descriptions of its making and use appeared more commonly than before. Aside from new editions of Borough and Bourne, for example, we find just such an account in Thomas Hood’s 1596 The Use of the Two Mathematicall Instruments. The title-page of this book carries a note that ‘The Staues are to be sold in Marke lane, at the house of Francis Cooke’, though Cooke was not an instrument maker and can only have been an intermediary.75 Around this time Thomas Blundeville wrote that the cross-staff was ‘commonly used in these dayes’.76 And, following Hood’s text, there were a number of works that feature the cross-staff: William Barlow’s Navigator’s Supply (1597), which concludes with the following couplet: ‘Let Staffe, Carde, Compasse, Ship, and Skill, / Depend upon Gods blessed will’, and Edward Wright’s Certaine Errors in Navigation (1599), which dedicates a chapter to the specific difficulties of observing with the cross-staff (mainly having to do with the problem of placing the staff correctly against the eye, and correcting for the height of the observer above the water77).