[154] Extract from memoranda of October 5, 1855:—
‘By constant observation, to lay down position and course of ship, and correct compasses.
‘To record speed of ship through water by logs.
‘Revolution of engines.
‘Force and direction of wind.
‘Draught and trim of ship, sails carried, &c.
‘Temperature and peculiarities of sea water.
‘As the result of these observations, to plot down hour by hour the position of the ship, to compute the speed, variations of compass, the direction and force of current, and true direction and force of the wind.’
[155] Mr. Brunel also proposed to have charts prepared for the route of the great ship to Australia and Calcutta, similar in character to some which were made under his directions for the route of the ‘Great Western’ to New York, which he described as follows:—
‘When we started the “Great Western” to New York, I had a chart drawn and engraved of the sea (that is, the lines of latitude and longitude, and the bearings of the compass, and the coast and soundings) on a cylindrical projection of a great circle from Bristol to New York; and we found it very useful for the captain to see his great circle sailing, and to see how much he was deviating from it.’