564 SPECIAL METHODS OF DISCOVERT. 



or new observations with the aid of known instruments or 

 methods, by employing new or improved instruments or 

 modes of observation, by means of more intelligent and 

 acute observation, &c. &c. 



An immense number of discoveries in geography, 

 meteorology, atmospheric phenomena, the tides, botany, 

 natural history, geology, climatology, mineralogy, physics, 

 and other subjects, have been made in consequence of the 

 facilities of observation afforded by navigation and travel ; 

 and the rules to be followed in order to be able to take 

 the greatest advantage of such circumstances are fully 

 described in Herschel's ' Admiralty Manual of Scientific 

 Inquiry.' Observations made during foreign travel have 

 enriched mankind with a knowledge of a great number 

 of useful foods, fruits, minerals, and other substances. As 

 even an enumeration merely of these substances would too 

 largely extend the size of this book, I shall only refer 

 to the discovery of caoutchouc : c Indiarubber appears, 

 under the name of caoutchouc, to have been known in 

 Europe only as a very rare curiosity about the beginning 

 of the eighteenth century. Nothing was known of its 

 production, except that it was obtained from a tree in 

 America, till the French Academicians went to South 

 America (Quito) to measure a degree of meridian. M. 

 de la Condamine, who was one of the party, sent an 

 account of its source to the French Academy in the year 

 1736. Don Pedro Maldonado, who was another member 

 of the expedition, found the same variety of indiarubber 

 tree on the banks of the Amazon. M. Fresnau discovered 

 an india-rubber-yielding tree at Cayenne, and forwarded 

 an account of it to the French Academy in 1751.' 

 Although our neighbours were so busy with this sub- 

 stance, the first published notice of it in this country did 

 not take place till the year 1770, when Dr. Priestley in a 



