on the Progress of' the Useful Arts. 171 



part of the sea. Though the needle had been perfect in its di- 

 rection, and though the log were improved to the utmost, there 

 would still exist the necessity for some other guide, whence the 

 effect of currents might be eliminated. The mariner sees no- 

 thing around him but the monotonous wave, and, conscious that 

 the ocean on which his log swims may itself be moving onward, 

 looks anxiously for some object uninfluenced by the stream. 

 The stars alone can supply, in every situation, an unchanging 

 guide, and a knowledge of their movements becomes essential to 

 the seaman. But the science of astronomy is one founded on a 

 long series of observations, and which has only reached a suffi- 

 cient exactitude with the assistance of many collateral aids. 



The observations of the ancient astronomers, made by means 

 of the rude gnomon and clypsedra, derive value from their mere 

 antiquity ; the errors incident to them being rendered insensible 

 by subdivision among so many epochs. But such observations 

 would never have enabled us to attain to that degree of preci- 

 sion which the mariner demands ; and the true nautical astro- 

 nomy was only founded when Galileo turned his telescope to the 

 stars. The labours of Tycho, of Kepler, of Guericke, the deep 

 studies of the Bernoullis, of Euler, of Newton, of Maclaurin, 

 of Lagrange, and of Laplace, were all steps essential to the per- 

 fection of the nautical art ; the multiplicity of these steps pre- 

 vent their detail, but there is one among them whose importance 

 stands so pre-eminent, that it would be unfair to Scotland and 

 to its author to pass it over in silence. The illustrious Kepler 

 had been toiling through endless calculations to demonstrate the 

 true figures of the planetary orbit ; and the fearful truth was 

 just breaking upon his mind that human life is too short, and 

 that human endurance is too limited for the necessary labour, 

 when our own Napier presented to the scientific world the Lo» 

 garithmic Canon. There is not a ship-boy who is unacquaint- 

 ed with the power of the logarithmic calculus, or who has not 

 reason to turn his face every day towards the tower of Merchis- 

 ton, and thank that giant mind which first opened the spring 

 whence such wide-spreading benefits have flowed. Even with 

 all the assistance which the logarithms have given, the labour is 

 still regarded by many as excessive ; and when newly out of 

 sight of the West India Islands, all hands have been called on 



