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Updated: June 28, 2025
He provided himself with a cross-staff for determining the angular distance between stars or other objects, and, finding the divisions of the scale inaccurate, constructed a table of corrections, an improvement that seems to have been a decided innovation, the previous practice having been to use the best available instrument and ignore its errors.
Before the knights began the recital of their complaints, however, Becket appears to have become alarmed at the demeanour of the four men, who afterwards admitted that they thought of killing him then and there with the only weapon that was handy a cross-staff that lay at his feet.
The compass was then brought down to a divided circle, by which means the number of degrees in the apparent angular distance of the two stars was determined. His next advance in instrumental equipment was to provide himself with the contrivance known as the "cross-staff," which he used to observe the stars whenever opportunity offered.
But some kind of a dratted cross-current ketched me and I'm sailin' out to sea, I finds, without compass or cross-staff. Bound to get to London River, eh, Jack, same as we started out on the silly little raft." "Whew, this adventure was bad enough," cried Jack, "but when you saw Ned Rackham's pirates in the boat, and you couldn't run away, I wonder, honest, Joe, you didn't die of fright."
No doubt the cross-staff is a very primitive contrivance, but when handled by one so skilful as Tycho it afforded results of considerable accuracy. I would recommend any reader who may have a taste for such pursuits to construct a cross-staff for himself, and see what measurements he can accomplish with its aid.
The introduction of the sextant greatly simplified taking reckonings at sea as well as facilitating taking the correct longitude of distant places. Before that time the mariner was obliged to depend upon his compass, a cross-staff, or an astrolabe, a table of the sun's declination and a correction for the altitude of the polestar, and very inadequate and incorrect charts.
Hadley had invented the sextant, by which the sun's elevation could be taken with much more ease and accuracy than with the old cross-staff, the very rough gnomon which the earlier navigators had to use. Still more important for scientific geography was the improvement that had taken place in accurate chronometry.
This pilot shewed no surprise on seeing the large wooden and metal astrolabes belonging to the Portuguese, as the pilots of the Red Sea had long used brass triangular instruments and quadrants for astronomical observations, and that he and others who sailed from Cambaya, and the ports of India, navigated by the north and south stars, and the constellations of the eastern and western hemispheres; and, though they did not use these instruments in navigation, they employed one made of three pieces of board, similar to the balhestillia, or cross-staff of the Portuguese.
How far and in what direction the Plymouth Adventure had been blown by the storm was largely guesswork. By means of dead reckoning and the compass and cross-staff, Captain Wellsby hoped to work out a position but meanwhile he scanned the sea with a sense of brooding anxiety.
He rubbed his eyes, looked again, adjusting his observation by a cross-staff which had been placed so as to bear upon the point. And behold, the light increased, like a comet to the eye of the astronomer, "with fear of change perplexing nations." "The Lord preserve us!" said Caxon, "what's to be done now? But there will be wiser heads than mine to look to that, sae I'se e'en fire the beacon."
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