August 12, iS8o] 



NA TURE 



351 



cases the body is changed into a denser variety, whence may be 

 inferred that the state taken by matter is in relation to the 

 volume it is obliged to occupy under action of external forces. 

 This (M. Spring points out) is merely the generalisation of a 

 well-known fact. Some curious results are deduced from it. 

 The researches described have important bearings on mineralogy 

 and geolog)-. 



Mr. R. Crowe of Liverpool communicates to the British 

 Journal of Photography an account of some attempts to photo- 

 graph a landscape by the aid of lightning-flashes. A gelatine 

 plate, requiring by day an exposure of two seconds, was exposed 

 from 10.15 P-™- ''3 l°-45 P-ui-. during which time there were 

 120 brilliant flashes and about half as many minor ones. Most 

 of these were in a horizontal direction, and five or .six of then 

 were imprinted on the negative. A perpendicular fla* which 

 struck a church-tower half a mile away was rendered with ex- 

 traordinary sharpness and brilliancy. The surrounding objects, 

 in spite of the long exposure, were but feebly impressed; 

 whence Mr. Crowe argues that though the light of a flash of 

 lightning is of a very actinic character, there still is not sufficient 

 volume of light to illuminate a landscape or building to allow a 

 successful photograph to be taken. Mr. Crowe further suggests 

 that an attempt should be made to photograph, for scientific 

 purposes of reference, the varied forms assumed by lightning at 

 different times and in different countries. 



GEOGRAPHICAL NOTES 



News has been received from Zanzibar that Capt. Carter and 

 Mr. Cadenhead, of the Belgian Exploration Expedition, have 

 been killed by the chief " Wrambo." This is probably the 

 chief Mirambo, who formerly caused so much trouble to 

 explorers between Zanzibar and Lake Tanganyika, but of whom 

 Mr. Stanley gives so good a report in his last work. It was 

 Capt. Carter who was so successful in the introduction of Indian 

 elephants into Africa. 



The August number of the Geographical Society's Proceed- 

 ings contains Mr. im Thurm's paper on his journey in British 

 Guiana, already noticed in our columns, but the principal 

 feature this month is of course the paper on Kuldja by Major 

 F. C. H. Clarke, R.A., a well-known military writer on Eastern 

 affairs. After a useful historical sketch. Major Clarke deals suc- 

 cessively with the geography, orography, rivers, communications, 

 towns, population, climate, vegetable products, and minerals of 

 the region, and furnishes much interesting information, collected 

 with evident care. This paper is followed by an account of M. 

 Severtsoff's j ourney in Ferghana and the Pamir, from a transla- 

 tion by M. Alexis LomonossoH, of the Russian Geographical 

 Society. The geographical notes furnish information respecting 

 the East African Expedition, the climate of Matabele-land, the 

 recent obsen-ations of Dr. Matteucci in Kordofan, and Dr. 

 Gerhard Rohlfs' account of the Jofra oasis. After notes on 

 American Arctic expeditions and the position of the Crozet 

 Islands, we have Mr. Whymper's account of his ascent of the 

 famous Antisana mountain in South America, and lastly Mr. A. 

 Forrest's own narrative of his journey through North-Western 

 Australia. Two maps are given with the present number, one 

 of British Guiana, which is very acceptable, and the other of 

 the Kuldja district and the Russo-Chinese frontier in Turkistan. 



With the August number of their Herald the Baptist 

 Missionary Society publish a map of Equatorial Africa, which, 

 though presumably not laying claim to scientific accuracy, is of 

 interest as showing \\hat an immense region can be reached by 

 means of the River Congo and its affluents. The map is intended 

 to illustrate the scheme which Mr. Arthington has sketched out 

 for the application of his last munificent donation to the Society. 

 The geographical part of this great task consists in the explora- 

 tion of the Nkutu and Ikelemba Rivers, the two principal 

 tributaries of the Congo from the south, after passing Stanley 

 Pool, and the opening of a route towards Lake Albert, along the 

 Mbura River, which enters the Congo above Stanley's Ara- 

 wimi. 



M. C. E. DE UjFALvy left Paris in July to undertake a new 

 and important journey in Central Asia. He goes in the first 

 instance to Orenburg, and thence to Tashkend, where he hopes 

 to arrive at the end of next month. He contemplates staying 

 the winter at Samarkand, and will commence his explorations 

 next spring. His programme is an extensive one, and embraces 



a considerable part of the Southern Pamir region. In the course 

 of his labours he will visit the Upper Zarafshan valley, Karategin, 

 Wakhan, Shignan, Badakshan, and probably Afghanistan. The 

 return journey will, if possible, be made through Persia and the 

 Caucasus. 



News has arrived in Paris that a French mission has reached 

 Segon Sokkova and has been well received by King Ahmadan. 

 M. Soleillet, who is on his way to Senegal, is not a member of 

 this expedition, and will proceed by another route to the same 

 city. 



The TVeijiiar Gazette states that Dr. Gerhard Rholfs is about 

 to set out for Abyssinia, accompanied by Dr. Stecker, who will 

 attempt a new exploration in Central Africa. 



It is stated that a fifth Belgian Expedition is about to start 

 for Africa, intended to reinforce the expedition on the Congo 

 under Mr. Stanley. It will be commanded by Lieut. Braconnier. 



The August number of Petennann's Mittheilungen contains 

 an exhaustive article by Dr. Behm on the Island of Rodriguez, 

 accompanied by a very clear map. Bernhard v. Struve discusses 

 the question of an inland trade-route through Siberia. An ex- 

 cellent hydrographical article, with a large-scale chart, on the 

 Lower W'eser from Bremen to Bremerhaven, is contributed by 

 Oherb.iu-Director L. Franzius of Bremen. The results of the 

 various East African International Expeditions are described. 

 The researches of the Danish schooner Ingolf in the seas around 

 Iceland in 1S79 are described by H. Wiehmann. 



The London Missionary Society have received intelligence of 

 the safe arrival of their new Tanganyika Expedition at Zanzibar 

 on May 29. The party is composed of the Revs. A. J. Wookey 

 and D. Williams, with Dr. Palmer as medical assistant. When 

 the last mail left, an efficient leader and some of the head-men 

 had already been engaged, and they hoped to start for the interior 

 early in July. 



The Chm-ch Missionary Society are sending out further rein- 

 forcements for their Nyanza mission. The Rev. P. O'Flaherty, 

 an able Oriental scholar, who was an interpreter on Lord 

 Raglan's staff in the Crimean war, left for Zanzibar early in July, 

 and will probably accompany the Waganda chiefs on their 

 journey back to Lake Victoria. Mr. W. E. Taylor, of Hertford 

 CoUe'^e, Oxford, who has been trained as a medical missionary, 

 and Mr. A. J. Biddlecombe have, we •believe, just started for 

 East Africa, and will in the first instance join Mr. Copplestone 

 at Uyui. 



L' Exploration for August 5 contains some interesting extracts 

 from the letters of Col. Prejevalsky, describing the difficulties 

 he had to encounter in attempting to reach Lhassa, in which he 

 was foiled. The intrepid Colonel has evidently succeeded m 

 making considerable natural history collections. 



THE STRUCTURE AND ORIGIN OF CORAL 



REEFS AND ISLANDS^ 

 TiARWIN'S THEORY.— During the voyage of the Beagle 

 ^ and subsequently, Mr. Darwin made a profound study of 

 coral reefs, and has given a theory of their mode of formation 

 which has since been universally accepted by scientific men. 



Darwin's theory may be said to rest on two facts— the one 

 physiolo-Jical, and the other physical— the former, that those 

 species of corals whose skeletons chiefly make up reefs cannot 

 live in depths greater than from 20 to 30 fathoms ; the latter, 

 that the surface of the earth is continually undergoing slow 

 elevation or subsidence. _ , ,, ■, u 



The corals commence by growing up from the shallow waters 

 surrounding an island, and form a fringing reef which is closely 

 attached to the shore. The island slowly sinks, but the corals 

 continually grow upwards, and keep the upper surface of the 

 reef at a level with the waves of the ocean. When this has gone 

 on for some time a wide navigable water channel is formed 

 between the reef and the shores of the island, and we have a 

 barrier reef These processes have but to be continued some 

 sta-'es further, when the island will disappear beneath the ocean, 

 and be replaced by an atoll with its lagoon where the island once 



^ "According to this simple and beautiful theory, the fringing 

 . Abstract ot paper read at the Royal Society o£ Edinburgh by Mr. 

 John Murray. (PubUshed by permission of the Lords Commissioners of the 

 Treasury.) 



