Heading for Trouble

The Perils of Navigation

The first & most principal thing for any seafaring man or traveller, is to know toward what part of the Earth he

meaneth to go.

Gresham College and the British Society for the History of Mathematics

present

Stephen Johnston

History from below: mathematics, instruments and archaeology

Thursday 3 November, 6pm

The pilots took the north, marking it, and found that the compasses northwested a full point; and the sailors were fearful and distressed. The Admiral ordered that the north again be marked when dawn came, and they found that the compasses were correct. The cause was that the North Star appears to move and not the compasses.

He that diligently observes the variation, finds (as I say) no prejudice in it, only it requires daily, or once in two or three days half an hours work, and this labour it doth abundantly recompense; for by this means he knows at the present how to direct his Course, and for the future… he knows when he draws near to any of those places where such observations were made, and so falls the more certainly with any place intended.

… knowledge of the Variation of the Compassed; yea besides the particular knowledge of Places, the expert Navigator stand in great hope hereby to attain unto good help for the finding of Longitudes

Exact truth amongst the constant waves of the sea is not to bee looked for, though good instruments bee never so well applied… Causes of error herein, some cannot be avoided, as the unsteadiness of the ship, the imperfection of sense & instruments, the weak respective force of the needle or wires, be they never so well touched. Others may be eschewed, as that there be no iron near the Compass in time of observation…

in the place where Sir Thomas Button did winter in 57 degrees of latitude, the constant great tides every twelve hours, and the increase of those tides whensoever any strong western wind did blow, doe strongly persuade us that the main Western Ocean is not far from thence; which was much confirmed onto them the summer following; when sailing directly North from that place where they wintered, about the latitude of 60 degrees, they were crossed by a strong Currant running, sometimes Eastward, sometimes Westward: So that … wee may assure our selves that from thence we may with great ease pass to any part of the East Indies.

the Cape of California, which is now found to be an island

I have observed that some of our masters take a wise course, in not trusting to those courses which are showed by their charts. But first getting themselves into the height or parallel of the place to which they are going: and withal, knowing assuredly whether they be more eastward or westward than that place; they then proceed always heedfully keeping themselves under that parallel till they come to the place desired. Then which way of sailing there is none indeed more certain and infallible for the sure finding of the place assigned.

coming

Mondays at One

For those in peril on the sea

March 2006