July 25, 1889] 



NATURE 



291 



lake bottom ; and that, when this blister-like elevation 

 subsides, the island is submerged and disappears. 



When sticks are forcibly pushed into the materials 

 composing the floating island, abundant bubbles of gas 

 are given off, the evolution of the gas being accompanied 

 by the production of a very perceptible odour. 



During the 150 years or more, over which the records 

 so carefully collected by Mr. Symons extend, there are 

 nearly forty during which appearances of the island have 

 been noticed. Sometimes, however, intervals of as much 

 as ten years have elapsed without any appearance of the 

 island ; at other times the island has been seen for a 

 number of years in succession ; and not unfrequently it 

 has risen and sunk several times in the course of the 

 same year. 



The island only rises in hot weather. By far the most 

 common period for the appearance of the island has 

 been the months of July and August ; never has it been 

 known to appear before June 5, and only once has it 

 remained up after October 8. An examination of the tem- 

 perature-records of the lake-waters and of the atmosphere 

 in the neighbourhood points to the conclusion that the 

 years marked by the appearance of the island are those 

 in which the summer has been exceptionally hot. 



To come now to the serious attempts which have been 

 made to investigate the nature and causes of this inter- 

 esting phenomenon. We may pass over the hasty and 

 crude guesses of Hutchinson, Clarke, Budworth, and 

 others, and notice first the valuable investigation of 

 Jonathan Otley, the author of the well-known Lake- 

 Guide. Otley had the great advantage of the advice and 

 co-operation of the celebrated Dr. John Dalton, himself 

 a native of the district, who analyzed the gases collected 

 from the " floating island.'' Otley and Dalton's observa- 

 tions were made between the years 1814 and 1830. 



In 1874, Dr. Alexander Knight, of Keswick, laid before 

 the Literary and Scientific Society of that town a series 

 of careful observations and judicious inferences concerning 

 the floating island; and in 1876, Sir G. B. Airy took a 

 number of bearings on the floating island, so as to fix its 

 €xact position. 



Such was the state of knowledge upon the subject when 

 the author of the present memoir took up the investiga- 

 tion. In August 1884 he visited the island in company 

 with Prof. Sylvester and some other friends, and made a 

 set of careful investigations concerning the position and 

 size of the island, the nature of the materials composing 

 it, the gases given off from it, and the temperature of the 

 water around. A second visit, in August 1886, enabled 

 the author to see the island when at the bottom of the 

 lake. 



In September 1887, Captain Wharton, R.N., F.R.S., 

 Hydrographer to the Admiralty, obtained a section of the 

 island by pushing a tube through the peaty mass forming 

 the island itself down into the lake bottom. The peat 

 was found to rest on a layer, only a few inches thick, of a 

 diatomaceous earth. 



The gases collected by Mr. Symons, Captain Wharton, 

 and several other observers, have been analyzed by Dr. 

 W. J. Russell, F.R.S. The results obtained(;are in close 

 agreement with those of Dalton. The gas evolved 

 appears to be a mixture, in nearly equal volumes, of marsh 

 .gas_and nitrogen, with only small quantities of carbonic 



acid and oxygen. Dr. Russell points out that the com- 

 position of this gas is nearly identical with that of a 

 " fire-damp " from Killingworth Colliery analyzed by 

 Graham. 



That the " mystery " in connection with the floating 

 island of Derwentwater still remains unsolved is freely 

 admitted by the author of the work. It would seem that 

 during warm weather a sufficient evolution of gases takes 

 place to cause the peaty bottom of the lake at this point 

 to rise in a great blister. But what are the causes 

 that give rise to this evolution of gas at this particular 

 spot — an operation that has been repeated many times 

 during the last 150 years— it is not easy to suggest. 

 Equally difficult is it to assign a cause for the appear- 

 ance of this phenomenon at a definite point with such 

 remarkable persistency, while nothing of the kind has 

 been observed elsewhere. The peculiarities of the lake- 

 bottom at this place which may exist and may conduce 

 to such a result do not appear to have been as yet 

 determined. 



Mr. Symons calls attention to the numerous floating 

 islands at many different localities, which consist of 

 accumulated masses of vegetation that have accumulated 

 near a shore, and have subsequently broken loose. From 

 all such cases, as he points out, the Derwentwater Island 

 differs in three important particulars: (i) in being 

 usually at the bottom of the lake, and only floating for 

 perhaps one month in four years ; (2) in being a part of, 

 and remaining continuously united with, the bottom of 

 the lake ; (3) in always occupying the same spot. 



It is to be hoped that this able summary of the whole 

 evidence bearing on the question, which has been pre- 

 pared by Mr. Symons, may not only attract more general 

 attention to a very interesting phenomenon, but induce 

 some investigator with the necessary knowledge and 

 leisure to make such observations as are still necessary ■ 

 before we can hope for a complete explanation of the 

 exact causes to which it is to be assigned. 



A JOURNEY TO THE PLANET MARS. 



Mr. Stranger's Sealed Packet. By Hugh MacColl. 

 (London : Chatto and Windus, 1889.) 



A WORK of fiction, founded upon scientific facts, is 

 interesting to us, inasmuch as it may extend, to no 

 inconsiderable degree, the scientific knowledge of its 

 readers. Such attempts, however, to assimilate science 

 with fiction may have an injurious effect, unless treated 

 by one having an intimate knowledge of the phenomena 

 which he describes, and we have to congratulate the 

 author of this work upon his acquaintance with the 

 Cosmos, exhibited in this account of an imaginary journey 

 through interplanetary space. 



The many means devised by that clever author, 

 Jules Verne, for such a journey, are too well known to 

 need any comment here. Mr. MacColl lacks the minute- 

 ness of description pecuhar to Jules Verne, but neverthe- 

 less fabricates a " flying machine '"' that may rank with 

 the best products of tiiat author's ingenuity. 

 The principle employed is stated as follows ; — 

 The attracting force residing in every particle of 



