NATURE 



[April 3, 191; 



a two-shilling piece, and is as flat as those coins, 

 these jelly-fishes are not referable to that species. 



In life,' they are almost hemispherical and slightly 

 flattened on top ; the largest do not measure more than 

 16 mm. in their widest part, and the smallest measure 

 about 6 mm. 



The Norquane is a narrow- stream with a sandy 

 bed cut into a succession of pools by granite bars. In 

 all the pools over a distance of a mile, hundreds of 

 the jelly-fishes were to be seen. The first specimen 

 was found in a pool about 20 ft. by 30 ft. and 7 ft. 

 deep, late in the afternoon, and a careful search did 

 not at first reveal any more. Shortly after mi having 

 a bathe in the same pool, numerous specimens came 

 to the surface, and subsequent observation showed that 

 the creatures swim near the surface in the earlier part 

 of the dav, and retire to the deeper water during the 

 hotter hours, from which they were disturbed by the 

 bathing. Their stinging powers, however feeble, 

 probably render the jelly-fishes unpalatable to the fishes 

 in the pool (chiefly Barbus ■ymaculatus and Tilapia 

 sp.), which left them severely alone. 



I hope to be able soon to obtain Gunther's paper in 

 the O.J. MS. on Limnocnida tanganyikae, when it 

 will be possible to decide whether or not this is a new 

 and the fifth known species of fresh-water medusa. I 

 should add that a careful examination of several pools 

 during three days failed to reveal any signs of a 

 hvdrosome stage. G. Arnold. 



The Rhodesia Museum, Bulawayo, February 21. 



An Experiment for Showing Lines of Force in an 

 Electrostatic Field. 



The general directions of the lines of force between 

 charged conductors can be shown by a method which, 

 though extremely simple, shows as much as the 

 elegant but somewhat elaborate apparatus described 

 by Mr. R. F. D'Arcy (Nature, March 20) would seem 

 capable of. 



It is simply to allow a scrap of cotton-wool to fall 

 between the knobs of a Wimshurst machine, or 

 among any conductors connected with them. As soon 

 as the bit of fluff touches one of the conductors it 

 moves off rapidly along- a line of force. If the other 

 conductor is oppositely charged the fluff will strike 

 it, and again be repelled, usually in a slightly different 

 direction, thus traversing a different line of force, 

 and so on. 



The scrap of charged fluff moves so rapidly under 

 the electric forces that, owing to the persistence of 

 vision, the shape of its path is very evident, and, 

 owing to its lightness and the relatively great resist- 

 ance offered by the air to its motion, its path approxi- 

 mates very closely indeed to the line of force. 



Berwrd M. Neville. 



William Ellis School, London, N.W. 



Snail-cavities in Stones. 



Referring to Mr. E. W. Swanton's letter in Nature 

 of March 20, may I point out that the Agglestone 

 rock is a sandstone composed of quartz grains bound 

 together by a ferruginous cement. 



I believe the excavations of Helix aspersa on rock 

 surfaces are produced by chemical action, and that the 

 secretion only acts as a solvent where salts of lime 

 are present. This assumption seems reasonable on 

 the supposition that the snails require lime for the 

 construction of their shells. 



Sandstones, unless calcareous, would have to be 

 attacked mechanically by snails for cavities to be 

 formed. Is there any evidence to prove that such 

 cavities have been produced in sandstones? 



C. Caris-Wii son. 

 NO. 2266, VOL. 91] 



COMPLETION OF THE DISCOVERY OF 

 THE GREENLAND COASTS.* 



THE last part of the coast of Greenland to 

 remain undiscovered is the north-eastern 

 tract between Germania Land and the area reached 

 by Peary on his famous journey across the 

 northern ice-sheet to Independence Fiord. This 

 gap has been filled by the Danish expedition under 

 Erichsen, which discovered that instead of the 

 coast continuing in a fairly direct course from 

 Germania Land in 77° N. to Peary Land in 

 82^° N., Greenland projects in a long peninsula 

 for 5 to the east. The work of the supporting 

 parties of this expedition made some interesting 

 additions to the glacial geology of Greenland, 

 which have been published in Koch and 'Wegener's 

 memoir on the glacial observations. Erichsen"s 

 expedition achieved its object, but he and his two 

 companions, Hagen and the Eskimo Bronlund, 

 perished during the return journey. Bronlund 

 was able to reach nearest home. His body and 

 diary, with a map by Lieut. Hagen, w-ere found 

 by a search-party under Captain Koch. These 

 papers announced the success of the expedition 

 and its tragic end. The journals of Eiichsen and 

 Hagen were not recovered, and an expedition to 

 search for them was dispatched under Captain 

 Ejnar Mikkelsen in 1909. This expedition was 

 1 successful in recovering some messages left by 

 Erichsen in his depots, but it also nearly perished 

 on the return journey. 



The expedition sailed in a small sloop, the 

 Alabama, but its plans were disorganised at the 

 start. It called at the Faroe Islands to receive its 

 dogs. But of the fifty dogs which had been 

 bought in Greenland, twenty-three had died on 

 the voyage to the Faroes, and the rest were so 

 diseased that they had to be shot. The Alabama, 

 therefore, had to go to the Eskimo settlements in 

 south-eastern Greenland to buy dogs, and was 

 thus seriously delayed. The expedition reached 

 its base, Shannon Island (lat. 75 io' N.), on 

 August 27, and a party in the autumn sledged up 

 the eastern coast as far as Lambert's Land (79 ), 

 where they found Bronlund 's grave. After winter- 

 ing on Shannon Island, Captain Mikkelsen and 

 Lieutenant Iversen marched across the inland ice 

 to the head of Denmarks Fiord, which had been 

 discovered by Erichsen ; they searched its coasts, 

 found the site of Erichsen's camps, and recovered 

 the messages left in them. Mikkelsen had in- 

 tended to return to the Eskimo settlements on the 

 western coast through the strait which, according 

 to Peary, extends across northern Greenland ; but 

 this plan had to be abandoned when it was found 

 from one of Erichsen's notes that "the Peary 

 channel does not exist, Navy Cliff being con- 

 nected by land with Heilprin Land." The author 

 has commented severely on this mistake, but, con- 

 sidering the sufferings it caused him, his annoy- 

 ance is intelligible. 



1 "Lost in the Arctic." Being the Story of the Alabama Expedition, 

 Ey Ejnar Mikkelsen. Pp. xviii+400+plates. (London: W. 



