登陆注册
4703400000023

第23章

Closely resemble in general form and structure atoll-reefs.--Width and depth of the lagoon-channels.--Breaches through the reef in front of valleys, and generally on the leeward side.--Checks to the filling up of the lagoon-channels.--Size and constitution of the encircled islands.--Number of islands within the same reef.--Barrier-reefs of New Caledonia and Australia.--Position of the reef relative to the slope of the adjoining land.--Probable great thickness of barrier-reefs.

The term "barrier" has been generally applied to that vast reef which fronts the N.E. shore of Australia, and by most voyagers likewise to that on the western coast of New Caledonia. At one time I thought it convenient thus to restrict the term, but as these reefs are similar in structure, and in position relatively to the land, to those, which, like a wall with a deep moat within, encircle many smaller islands, I have classed them together. The reef, also, on the west coast of New Caledonia, circling round the extremities of the island, is an intermediate form between a small encircling reef and the Australian barrier, which stretches for a thousand miles in nearly a straight line.

The geographer Balbi has in effect described those barrier-reefs, which encircle moderately sized islands, by calling them atolls with high land rising from within their central expanse. The general resemblance between the reefs of the barrier and atoll classes may be seen in the small, but accurately reduced charts on Plate I. (The authorities from which these charts have been reduced, together with some remarks on them and descriptive of the Plates, are given separately.), and this resemblance can be further shown to extend to every part of the structure. Beginning with the outside of the reef; many scattered soundings off Gambier, Oualan, and some other encircled islands, show that close to the breakers there exists a narrow shelving margin, beyond which the ocean becomes suddenly unfathomable; but off the west coast of New Caledonia, Captain Kent (Dalrymple, "Hydrog. Mem." volume iii.) found no bottom with 150 fathoms, at two ships' length from the reef; so that the slope here must be nearly as precipitous as off the Maldiva atolls.

I can give little information regarding the kinds of corals which live on the outer margin. When I visited the reef at Tahiti, although it was low water, the surf was too violent for me to see the living masses; but, according to what I heard from some intelligent native chiefs, they resemble in their rounded and branchless forms, those on the margin of Keeling atoll. The extreme verge of the reef, which was visible between the breaking waves at low water, consisted of a rounded, convex, artificial-like breakwater, entirely coated with Nulliporae, and absolutely similar to that which I have described at Keeling atoll. From what I heard when at Tahiti, and from the writings of the Revs. W. Ellis and J.

Williams, I conclude that this peculiar structure is common to most of the encircled islands of the Society Archipelago. The reef within this mound or breakwater, has an extremely irregular surface, even more so than between the islets on the reef of Keeling atoll, with which alone (as there are no islets on the reef of Tahiti) it can properly be compared. At Tahiti, the reef is very irregular in width; but round many other encircled islands, for instance, Vanikoro or Gambier Islands (Figures 1 and 8, Plate I.), it is quite as regular, and of the same average width, as in true atolls. Most barrier-reefs on the inner side slope irregularly into the lagoon-channel (as the space of deep water separating the reef from the included land may be called), but at Vanikoro the reef slopes only for a short distance, and then terminates abruptly in a submarine wall, forty feet high,--a structure absolutely similar to that described by Chamisso in the Marshall atolls.

In the Society Archipelago, Ellis (Consult, on this and other points, the "Polynesian Researches," by the Rev. W. Ellis, an admirable work, full of curious information.) states, that the reefs generally lie at the distance of from one to one and a half miles, and, occasionally, even at more than three miles, from the shore. The central mountains are generally bordered by a fringe of flat, and often marshy, alluvial land, from one to four miles in width. This fringe consists of coral-sand and detritus thrown up from the lagoon-channel, and of soil washed down from the hills; it is an encroachment on the channel, analogous to that low and inner part of the islets in many atolls which is formed by the accumulation of matter from the lagoon. At Hogoleu (Figure 2, Plate I.), in the Caroline Archipelago (See "Hydrographical Mem." and the "Atlas of the Voyage of the 'Astrolabe'," by Captain Dumont D'Urville, page 428.), the reef on the south side is no less than twenty miles; on the east side, five; and on the north side, fourteen miles from the encircled high islands.

同类推荐
  • 华严感应缘起传

    华严感应缘起传

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 药师琉璃光如来消灾除难念诵仪轨

    药师琉璃光如来消灾除难念诵仪轨

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • The Cavalry General

    The Cavalry General

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 华严法界观门注

    华严法界观门注

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 二十四诗品

    二十四诗品

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
热门推荐
  • 爱在不言中

    爱在不言中

    1957年5月4日出生于长野县大町市。她的丈夫是著名推理小说家折原一。新津清美大学就读于青山学院大学文学部法语系。她常去听文化中心的小说写作讲座,在讲师山村正夫的鼓励下,新津清美开始投稿,1988年发表了处女作《双面胶小姐》,并登上了日本文坛。题材多取自日常生活,描写女性心理笔法精湛,善于恐怖风格。代表作有《夏娃的原罪》、《胎内余罪》、《流转》《危险的恩人》等。“男人和女人之间的事情,就连当事者自己也难以搞清楚啊。”
  • 阴阳部曲:误娶鬼娇妻

    阴阳部曲:误娶鬼娇妻

    前几天,一个陌生人让我用他的身份,和一个女人交往。那是一个美女,我果断答应了他的要求,但是和她交往之后,我的生活也发生了天翻地覆的变化……
  • 取悦你自己,才是正经事

    取悦你自己,才是正经事

    这是一本心灵励志书。以当下最流行的励志题材为主基调,在都市生活的大背景下,辅以锋利文笔,告诉人们该如何奋斗,如何去爱,以及如何去生活。整本书以“取悦自己”为独特视角,宣扬不迎合,不攀附,不将就,不求全的生活理念。针对18—35岁的读者,尤其是女性读者,注入强心剂。
  • 韩娱之寻觅

    韩娱之寻觅

    本书又名:金泰妍恋爱日常遇到一个我爱的,又爱我的人很难很难。既然遇到了,就不要脸的,肉麻的,狂撒狗粮的,狠狠幸福一辈子吧!新书文娱之小演员的日常已发布,讲的是我社长的爱情故事,感兴趣的就来帮作者我增加一下收藏呗!
  • 领导魔法(完全智慧手册丛书)

    领导魔法(完全智慧手册丛书)

    领导就是团队的领袖,是保证组织或企业实现大目标的舵手。一个成功的领导,不仅要具备娴熟的驭人技巧,卓越的预见力,而且需要有争取掌控领导权的非凡才能。只有拥有领袖的品质,才有可能成就非凡的事业。没有一个人是天生的领袖,然而一流的人才都具有学习模仿伟大人物的天赋,兴趣和热情。认识领袖的魅力,撑握统御大众的方法,就如同手握着实现宏伟理想的魔仗。本书全面论述进了新领导学的思想,积极探讨了统领人物的两极性、倾向性、深刻性、以及领导权应该具备的效能性和稳定性,充分肯定了领导者在权力动作过程中的智性发挥的应急才能和热情理智,是研究新领导学的一本重要参考书。
  • 幸运草

    幸运草

    有人说,假如能寻获一片由四瓣心形叶片合成的幸运草,他(她)就能拥有永恒的幸福?!花语、风筝、芦花、黑茧、幸运草……十六篇悬疑精彩、柔情优美、动人心弦的中、短篇小说,篇篇都娓述着一个浪漫、细腻、感人的故事!
  • 逆命魔主

    逆命魔主

    每一个命格,都是一条走向绝世传奇的路!武道世界,命格为王。命格不再是算命先生嘴里的虚言,而是真实存在的武道之基。‘疾风劲草’命格,让你刀出如风,身如疾岚。‘天火燎原’命格,让你挥掌释烈焰,如祝融降世。‘羽化登仙’命格,让你状若神仙,真有白日飞升之机。……身患绝症而死的陈重穿越到这奇异的武道世界,凭借着‘逆天改命’系统,一步步换命,改命,逆命,将自己从‘七日必死’的命格困境里拉出来,成就一代武道神话。
  • 向着未来的歌唱

    向着未来的歌唱

    又是一个金秋时节,苍翠的山林中,那金光烁烁的橘子,硕动着微醺的橘,向着未来的歌唱!
  • 生活新探

    生活新探

    科学是人类进步的第一推动力,而科学知识的普及则是实现这一推动的必由之路。在新的时代,社会的进步、科技的发展、人们生活水平的不断提高,为我们青少年的科普教育提供了新的契机。抓住这个契机,大力普及科学知识,传播科学精神,提高青少年的科学素质,是我们全社会的重要课题。
  • 吃货皇后

    吃货皇后

    柳莹莹是个喜欢吃东西的人,她对于好吃的非常的有研究,喜欢吃好吃的东西,更加喜欢做好吃的东西。--情节虚构,请勿模仿