In endeavouring to meet this demand it must be premised, that while the main object proposed in this volume is to treat of the early indications of the island now recognized as Australia, anterior to the time of Captain Cook, it is impossible to deal with the real or supposed discoveries which may have taken place prior to that date, without referring at the same time to the discovery of the adjacent island of New Guinea and of the great southern continent, of both of which what we now call Australia was in those times regarded as forming a part. The investigation is one of the most interesting character in all its stages, but beset with doubts and difficulties arising from a variety of causes. The entire period up to the time of Dampier, ranging over two centuries, presents these two phases of obscurity; that in the sixteenth century (the period of the Portuguese and Spanish discoveries) there are _indications_ on maps of the great probability of Australia having been already discovered, but with no written documents to confirm them; while in the seventeenth century there is documentary evidence that its coasts were touched upon or explored by a considerable number of Dutch voyagers, but the documents _immediately_ describing these voyages have not been found. That, in so far as regards the Portuguese, this obscurity is mainly due to a jealous apprehension lest lands of large extent and great importance in the southern seas might fall into the hands of rival powers to their own displacement or prejudice, may not only be suspected, but seems to be affirmable from historical evidence.