36 



Maskelyne's assistant at Greenwich, and the other was JAMES 

 COOK (1728-1779), the celebrated explorer. The two men 

 were associated in the first of Captain Cook's three great 

 voyages, that of 1768 to 1771, the object of which was part 

 astronomical to determine the distance of the sun by observa- 

 tion of the transit of Venus of 1769, June i and partly for 

 discovery and maritime survey. 



Cook had already earned a high reputation as a navigator, 

 having in 1759 been employed as master of the Mercury, 

 in which ship he rendered important service to General Wolfe 

 then attacking Quebec, by taking soundings in the River 

 St. Lawrence so as to enable the fleet to take up safe posi- 

 tions. He made a complete survey of the intricate channels 

 of the river below Quebec, and for many years his chart 

 was the guide for navigation there. Sir WILLIAM WHARTON 

 (1843-1905), the late Hydrographer of the Admiralty, wrote 

 of this work : " Cook was indeed a born surveyor. Before 

 his day charts were of the crudest description, and he must 

 have somehow acquired a considerable knowledge of trigon- 

 ometry, and possessed an intuitive faculty for practically 

 applying it, to enable him to originate, as it may truly be 

 said he did, the art of modern marine surveying." The 

 survey of the island of Newfoundland followed and employed 

 him for several years. The accuracy of his charts of this 

 coast is truly astonishing, and they are not yet wholly 

 superseded by the more detailed surveys of modern times. 



The second method of determining the longitude at sea, 

 namely, by means of watches that can be trusted to keep a 

 steady rate for long periods, had already been solved by the 

 invention of John Harrison's " timekeeper," and this had 

 passed a successful test, in 1761, in the course of a voyage 

 to Jamaica. In 1763 Charles Green had accompanied 

 Maskelyne, who shortly afterwards became Astronomer 

 Royal, in a voyage to Barbados in order to test another of 

 Harrison's " timekeepers " ; but none of these were supplied 

 to Cook and Green in 1768, and therefore they had to rely 

 entirely upon the methods of lunars. Wharton remarks 

 that " In these observations, Green was indefatigable. Cook, 

 an excellent observer himself, frequently took part in them, 

 but it was Green's especial business, and no doubt to him 

 is due the major part of the determinations of accurate 

 longitude which is one of the very remarkable points of this 

 voyage." 



One of the most striking points, when we consider the 

 surveys executed by Cook on his three voyages, is the way 



