NATURE 



93 



THURSDAY, JUNE 28, 1900. 



CHRISTMAS ISLAND. 

 A Monos^raph of Christmas Island {Indian Ocean); 

 Physical Features ana Geology. By C. W. Andrews, 

 with descriptions of the Fauna and Flora by 

 numerous contributors. Pp. xv + 237. (London : 

 Published by order of the Trustees of the British 

 Museum, 1900.) 



TILL 1887 Christmas Island, which is situated in the 

 Indian Ocean nearly a degree to the south-south- 

 west of Batavia, was scarcely known, even by name, to 

 the average Englishman, and only the low-lying shore 

 had been visited by explorers ; the steep cliffs, together 

 with the forest with which the island is cloth«d, forming 

 a barrier which had hitherto prevented access to the 

 central plateau. In that year the Commander of H.M.S. 

 Egeria, with the assistance of a landing party, succeeded 

 in cutting his way into the interior ; and two years later 

 the island was leased by the British Government to a 

 trading company. Since it contains an area of about 

 forty-three square miles, and appears never to have been 

 inhabited by aboriginal tribes, it presented a most favour- 

 able opportunity for studying the fauna and flora of an 

 oceanic island of considerable size situated at no very 

 great distance from a considerable land-mass — the Sunda 

 Archipelago Down to the time mentioned, it appears, 

 indeed, to have been the largest uninhabited tropical 

 island extant ; and as the discovery of valuable deposits 

 of phosphates in the interior indicated that its pristine 

 conditions would soon be rudely disturbed, it was evident 

 that if a biological survey was to be undertaken at all, 

 there was no time to be bst. Fortunately, Sir John 

 Murray interested himself strongly in the matter, and it 

 was eventually arranged that Mr. C. W. Andrews, of the 

 British Museum, who is both a geologist and a zoologist, 

 should undertake the work. He accordingly spent ten 

 months on the island during the years 1897-98 ; and the 

 present volume, in which he has had the assistance of 

 a number of specialists, is the result of his labours. 



As is evident by their permitting a member of their 

 staff to undertake the task, the Trustees of the British 

 Museum gave their support to the exploration ; and it is 

 a matter for congratulation that they have seen fit to 

 publish the results in the same form as the Museum 

 " Catalogues." A wise liberality has been exercised in 

 the matter of illustration, the plates (some coloured) 

 being numerous, while a considerable number of repro- 

 ductions from photographs are given in the text. These 

 latter have, however, received but scant justice at the 

 hands of the printer ; and it is, indeed, with some sur- 

 prise that we notice the volume bears the name of a 

 local firm of printers. 



Situated at a distance of over 190 miles from the 

 nearest land, with the intervening ocean attaining a 

 depth of more than three miles, Christmas Island appears 

 to have derived its limited fauna from the Sunda Archi- 

 pelago, of which indeed it probably once formed a part. 

 The length of its isolation is, however, indicated by the 

 circumstance that four out of its five indigenous mammals 

 are peculiar species, the fifth— a Shrew— being a local 

 NO 1600. VOL. 62] 



variety of an Assam and Tenasserim form. The majority 

 of the few land birds are likewise distinct, the most 

 striking being a Goshawk {Astur natalis), an Owl 

 {Ninox ?tatalis), and a White-eye {Zosterops natalis), 

 specimens of all of which were first collected by Mr, 

 J. J. Lister during a flying visit to the island in 1890. 

 As regards the fauna generally, it exhibits no greater 

 evidence of affinity with that of the Mentavvei chain of 

 islands, running parallel with Sumatra and Java, than 

 with that of the two islands last named. And the hypo- 

 thesis that Christmas Island formed the termination of 

 a "Mentawei Peninsula" must accordingly be given up. 



One of the main objects of the exploration of the 

 island was to ascertain whether its geological structure 

 would throw any further light on the vexed question of 

 the origin of atolls. As the result of his observations, 

 Mr. Andrews is led to believe that, from the absence of 

 a sufficient thickness of reef-limestone, Christmas Island, 

 although originally an atoll, could not have been formed 

 in the manner required by the Darwinian theory, as the 

 amount of subsidence which has taken place would have 

 been quite insufficient. That a certain amount of sub- 

 sidence may have occurred in the early history of the 

 island, Mr, Andrews considers to be quite possible. 



"It may, of course, be objected," he writes, "that 

 Christmas Island was never a typical atoll, and to this 

 objection no answer is possible ; but since it can be 

 shown that at one time it must have consisted of reefs 

 and islands approximating very nearly to those seen in 

 atolls which are regarded as typical, the determination 

 of the nature of the foundations upon which these reefs 

 and islands rested is at least a step in the right direc- 

 tion. ... In this case the basis of the island is almost 

 certainly a volcanic peak, the foot of which is now some 

 2400 fathoms below the level of the sea, and that on 

 its summits and flanks great accumulations of Tertiary 

 limestones have been deposited, and in some cases are 

 interstratified with the products of the eruptions, probably 

 for the most part submarine, which took place from time 

 to time. The oldest of the volcanic rocks are trachytic, 

 tlie newer basaltic. The last of the eruptions was ac- 

 companied by the formation of' thick beds of volcanic 

 ash, and it is upon these that the great mass of the 

 Miocene (Orbitoidal) limestones rests." 



The occurrence of such a thickness of Tertiary de- 

 posits (ranging from the Eocene or Oligocene upwards) 

 is unknown in any other oceanic island. It is important 

 to notice that these rocks, allowing for a difference in 

 the proximity of land at the time of their deposition, are 

 very similar to those of South Java ; but the author con- 

 siders that there are difficulties in believing that the 

 two series of sediments were deposited in a continuous 

 area, as this would involve great local dislocations. Ac- 

 cordingly the volcanic peak theory is adopted in preference 

 to such a view. 



In speaking of elevation and depression, the author is 

 careful to guard himself by stating that such terms are 

 merely used in relation to the sea-level ; and it would 

 appear, from reading between the lines, that he is rather 

 in favour of an actual alteration of the sea-level in these 

 districts. It may further be inferred that he does not 

 intend his conclusions as to the mode of origin of 

 Christmas Island to affect the case of other atolls, his 

 idea apparently being that all atolls are not of precisely 

 similar origin, 



K 



