登陆注册
4703400000007

第7章

Several theories have been advanced to explain the origin of atolls or lagoon-islands, but scarcely one to account for barrier-reefs. From the limited depths at which reef-building polypifers can flourish, taken into consideration with certain other circumstances, we are compelled to conclude, as it will be seen, that both in atolls and barrier-reefs, the foundation on which the coral was primarily attached, has subsided; and that during this downward movement, the reefs have grown upwards. This conclusion, it will be further seen, explains most satisfactorily the outline and general form of atolls and barrier-reefs, and likewise certain peculiarities in their structure. The distribution, also, of the different kinds of coral-reefs, and their position with relation to the areas of recent elevation, and to the points subject to volcanic eruptions, fully accord with this theory of their origin. (A brief account of my views on coral formations, now published in my Journal of Researches, was read May 31st, 1837, before the Geological Society, and an abstract has appeared in the Proceedings.)

(DESCRIPTION OF THE PLATES.

PLATE I.--MAP SHOWING THE RESEMBLANCE IN FORM BETWEEN BARRIER CORAL-REEFS SURROUNDING MOUNTAINOUS ISLANDS, AND ATOLLS OR LAGOON ISLANDS.)

In the several original surveys, from which the small plans on this plate have been reduced, the coral-reefs are engraved in very different styles.

For the sake of uniformity, I have adopted the style used in the charts of the Chagos Archipelago, published by the East Indian Company, from the survey by Captain Moresby and Lieutenant Powell. The surface of the reef, which dries at low water, is represented by a surface with small crosses: the coral-islets on the reef are marked by small linear spaces, on which a few cocoa-nut trees, out of all proportion too large, have been introduced for the sake of clearness. The entire ANNULAR REEF, which when surrounding an open expanse of water, forms an "atoll," and when surrounding one or more high islands, forms an encircling "barrier-reef," has a nearly uniform structure. The reefs in some of the original surveys are represented merely by a single line with crosses, so that their breadth is not given; I have had such reefs engraved of the width usually attained by coral-reefs.

I have not thought it worth while to introduce all those small and very numerous reefs, which occur within the lagoons of most atolls and within the lagoon-channels of most barrier-reefs, and which stand either isolated, or are attached to the shores of the reef or land. At Peros Banhos none of the lagoon-reefs rise to the surface of the water; a few of them have been introduced, and are marked by plain dotted circles. A few of the deepest soundings are laid down within each reef; they are in fathoms, of six English feet.

Figure 1.--VANIKORO, situated in the western part of the South Pacific; taken from the survey by Captain D'Urville in the "Astrolabe;" the soundings on the southern side of the island, namely, from thirty to forty fathoms, are given from the voyage of the Chev. Dillon; the other soundings are laid down from the survey by D'Urville; height of the summit of the island is 3,032 feet. The principal small detached reefs within the lagoon-channel have in this instance been represented. The southern shore of the island is narrowly fringed by a reef: if the engraver had carried this reef entirely round both islands, this figure would have served (by leaving out in imagination the barrier-reef) as a good specimen of an abruptly-sided island, surrounded by a reef of the fringing class.

Figure 2.--HOGOLEU, or ROUG, in the Caroline Archipelago; taken from the "Atlas of the Voyage of the 'Astrolabe,'" compiled from the surveys of Captains Duperrey and D'Urville; the depth of the immense lagoon-like space within the reef is not known.

Figure 3.--RAIATEA, in the Society Archipelago; from the map given in the quarto edition of "Cook's First Voyage;" it is probably not accurate.

Figure 4.--BOW, or HEYOU ATOLL (or lagoon-island), in the Low Archipelago, from the survey by Captain Beechey, R.N.; the lagoon is choked up with reefs, but the average greatest depth of about twenty fathoms, is given from the published account of the voyage.

Figure 5.--BOLABOLA, in the Society Archipelago, from the survey of Captain Duperrey in the "Coquille:" the soundings in this and the following figures have been altered from French feet to English fathoms; height of highest point of the island 4,026 feet.

Figure 6.--MAURUA, in the Society Archipelago; from the survey by Captain Duperrey in the "Coquille:" height of land about eight hundred feet.

Figure 7.--POUYNIPETE, or SENIAVINE, in the Caroline Archipelago; from the survey by Admiral Lutke.

Figure 8.--GAMBIER ISLANDS, in the southern part of the Low Archipelago; from the survey by Captain Beechey; height of highest island, 1,246 feet; the islands are surrounded by extensive and irregular reefs; the reef on the southern side is submerged.

Figure 9.--PEROS BANHOS ATOLL (or lagoon-island), in the Chagos group in the Indian Ocean; from the survey by Captain Moresby and Lieutenant Powell; not nearly all the small submerged reefs in the lagoon are represented; the annular reef on the southern side is submerged.

Figure 10.--KEELING, or COCOS ATOLL (or lagoon-island), in the Indian Ocean; from the survey by Captain Fitzroy; the lagoon south of the dotted line is very shallow, and is left almost bare at low water; the part north of the line is choked up with irregular reefs. The annular reef on the north-west side is broken, and blends into a shoal sandbank, on which the sea breaks.

同类推荐
  • 慈悲道场水忏法科注

    慈悲道场水忏法科注

    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。
  • 大丈夫论

    大丈夫论

    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。
  • 泰州道中却寄东京故

    泰州道中却寄东京故

    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。
  • 六十颂如理论

    六十颂如理论

    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。
  • 栖岩寺隋文帝马脑盏

    栖岩寺隋文帝马脑盏

    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
  • 辛辛苦苦三五年,风风光光五十年

    辛辛苦苦三五年,风风光光五十年

    现在的你,也许正为养家糊口忙得焦头烂额;也许还“蜗居”在几平米的小房间里,精打细算地过日子;也许还在朝九晚五,重复着枯燥的工作……要知道,即使是比尔·盖茨、巴菲特、李嘉诚、李开复这样的成功大师也经历过这样的苦日子,他们的成功之路也是这样走过来的。成功没有捷径,但可以走直线。
  • 欠债还钱(中篇小说)

    欠债还钱(中篇小说)

    我老爹说:“没出息的东西,你学会捡破烂啦?最好的女人,能厚着脸皮去给人家作小?想想那有多恶心!要我说,找这样的女人,还不如打光棍。要是不和她断了,你就别回这个家!”我和老爹几乎同时把电话撂了。我深深呼吸一口城市的空气,这才发现,城市的空气很呛人,就像碎玻璃那样刺痛了我的嗓子。我回头寻找叶红燕,她早已消逝在城市的夜色里了。
  • 清代圣人陆稼书演义

    清代圣人陆稼书演义

    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。
  • 城市老龄社会政策的演进及挑战

    城市老龄社会政策的演进及挑战

    随着中国社会老龄化的加剧,城市老龄社会政策日益引人关注。《城市老龄社会政策的演进及挑战》以城市人口年龄结构变迁为线索,梳理了在老龄化程度不同的社会环境下老龄政策的演变历程,进而分析现行老龄社会政策的创新点及局限性,展望高度老龄化社会来临时城市老龄社会政策的发展趋势。
  • 女侠如玉剑如虹

    女侠如玉剑如虹

    明朝嘉靖皇帝在位期间,武林暗潮涌动,六扇门为朝廷掌控武林的重要机构,六扇门为东厂权势滔天的奸宦逼迫,不得已牺牲总部头上官飞鸿,上官飞鸿逃避重重围捕,最终隐居于红云镇。二十年后,红云镇,上官飞鸿拼死拦住锦衣卫,让他的妻子,还有女儿逃跑,故事从那一个身着白衣,白发如雪,宛若天仙的女子,挥手之间救下上官瑶的那一刻,开始了。
  • 春天不再遥远

    春天不再遥远

    又闷又宅的剩女,在飘雪的冬夜,捡到一个醉酒的帅哥……于是开始了他们的爱情故事。--情节虚构,请勿模仿
  • 无与伦比的美好

    无与伦比的美好

    她是出身平凡热衷武术的欢脱少女,可宅可动却因感情黯然神伤。他是智商超群个性高冷的天才少年,却为她守候十年未变初心。一场跆拳道与咏春拳的切磋,让林悠悠与魏景尚相识相知。或许缘起只是一场乌龙误会,可当她亲眼看过他在武馆的迷人耀眼,便开始贪恋在他身边的青涩时光。没想到魏景尚也早已为率性特别的她悄悄心动。时光匆匆,余生好长,他有一个豪门的家庭和一个苛刻的母亲,而她纠缠于一段千疮百孔的感情和一个心心念念的梦想。可是没关系,我知道你会来,所以我愿意等。这十年来我每天都在想你,所以我可以自豪地说,我没有一天是在虚度时光。因为从遇见你的那一刻起,爱你便成为了我毕生的事业。
  • 新娘酷又拽

    新娘酷又拽

    十三岁,她喊他大叔,十四岁,她总爱破坏他的好事,十五岁,一杯药酒,她设计了他,从此爱上狼与小羊的游戏,十六岁,他傍上了别人,她离家出走。二十岁,她成了他的情人,原来,她一直逃不开,从他买下她的那天开始,一切都已经注定,就算拼命想躲都躲不掉!
  • 殷红的花朵

    殷红的花朵

    《殷红的花朵》是一部阐述追求爱情,抑扬善恶美丑的书。故事发生在1880年的英国,主人公马克·莱恩南经历了《春》、《夏》、《秋》三段生活的感情波澜。《春》描写了主人公在牛津大学求学时,受其导师年轻貌美的妻子诱惑的懵懂之恋;《夏》描写他从国外学成回国后,同一位婚姻生活不幸的议员夫人的炽热之恋;《秋》描写他成家成名后,他早年一位同学的独生女对他的痴情追求的成熟之恋。虽然三段恋情,却有机地联成一体。虽说是一部小说,然而文字却好像诗一样精美。《春》、《夏》、《秋》三个篇章,循序渐进,扣人心弦,感人之至,爱不释手。
  • 化身二次元萌妹

    化身二次元萌妹

    一觉醒来,叶岱飞惊愕的发现自己的灵魂居然在睡梦中穿越了时空,来到了一个各方面都比地球发达无数倍的异世界。最重要的是……他,变成了她,一个叫做“叶黛菲”的女孩。在这里,人类并非一支独大,他们与另一个可怕的物种争夺着星球的控制权;另外,人类中的天之骄子会在十七岁那年得到天赐能力,觉醒各种各样威力可怕的异能!而叶岱飞发觉自己这具身体的原主人便是这些天之骄子的其中一员,而她那原本无比鸡肋的变身天赐,也随着自己的灵魂附体,发生了翻天覆地的变化。一些只存在于动漫中的虚构女角色,竟是一个个的出现在了自己的变身卡片上……