290 



NATURE 



{July 25, 1889 



capable of detection by the use of chemicals carefully 

 painted on (such as dilute hydrochloric or oxalic acid 

 solution), on account of its fading out sooner under the 

 treatment. Stephen's blue-black ink is described as 

 composed of 15 parts galls, 5 ferrous sulphate, 4 iron 

 fihngs, 200 water, and \ indigo, in 3 of sulphuric acid, no 

 gum, or other thickening being mentioned, whilst other 

 inks usually contain a few per cents, of such substances, 

 copying-inks chiefly differing in containing sugar or 

 glycerine in addition. Sulphate of copper is stated to 

 be added occasionally to inks " with questionable ad- 

 vantage " ; the opinions of the vendors and users of steel 

 pens on this point being doubtless dissimilar. 



The major half of the book consists of a terse descrip- 

 tion of the general processes of manufacture, character- 

 istics, and modes of examination of dye-stuffs, classified 

 under the headings of nitro colouring matters, nitroso 

 colouring matters, aurin and its allies, phthaleins, azo 

 colouring matters, rosaniline and its allies, safranines and 

 indophenols, colouring matters from anthracene, sul- 

 phuretted and unclassified coal-tar dyes, and colouring 

 matters of natural origin. On reading the systematic 

 names of many of the artificial dye-stuffs, one can 

 hardly wonder that practical dyers prefer to employ 

 shorter and more colloquial terms, even though these 

 lack somewhat in scientific precision : " xylidene- 

 scarlet," for example, although not absolutely eupho- 

 nious, is still a much more pronounceable word than 

 sodium xylene - azo -beta - naphthol-alpha-disulphonate ; 

 whilst "night blue" is far less mouth-filhng than hydro- 

 chloride of tetra-methyl-tolyl-tri-amido-alpha-naphthyl- 

 diphenyl carbinol ! It is, however, to be regretted when 

 new dye-stuffs are designated by names already well 

 known in connection with substances of wholly different 

 chemical character : thus narcehie is ordinarily under- 

 stood to refer to one of the alkaloids of the opium 

 family ; but the term has also been applied to one of the 

 modern hydroxy-azo-naphthol dye-stuffs. In describing 

 the matter treated of in this section, the author is- well up 

 to date, such recent introductions to commerce as Green's 

 '' primuline," and the various derivatives thereof obtain- 

 able in situ on cotton goods by the " in-grain " process, 

 being included. Suggestions also as to the direction 

 which scientific investigation might take in improving 

 certain technical processes are not wanting : for example, 

 in the case of indigo dyeing, it is stated that a certain 

 amount of indigotin is always lost in the process of 

 reduction to white indigo, and its subsequent reoxidation ; 

 the cause of the loss being obscure, its investigation 

 would probably lead to means of preventing it which 

 would well repay the trouble. 



In every book, with the greatest amount of care and 

 vigilance, slips and misprints will inevitably occur : thus 

 on p. 165 it is stated that alkaloids generally have no 

 marked alkaline reaction on phenol phthalein, so that the 

 amount of acid combined in salts of morphine, quinine, 

 brucine, aniline, urea, &c., can be ascertained by titration 

 with standard acid, just as if no organic base were pre- 

 sent : obviously standard alkali is intended. Similarly, 

 on p. 234, methyl violet is described as " produced by the 

 direct oxidation of dimethyl aniline (from dimethyl tolui- 

 dme) " : the production of dimethyl aniline from dimethyl 

 toluidine is scarcely a commercial process, although the 



converse formation of toluidine and its homologues from 

 methylated aniline by " intra-molecular interchange " is- 

 i so. It says much for the care and attention bestowed 

 by the author in revising that such errata are but seldom 

 noticeable. C. R. Alder Wright. 



THE FLOATING ISLAND 

 DER WENT W A TER. 



IN 



The Floating Island in Derwentwater : its History and 

 Mystery. With Notes of other Dissimilar Islands. 

 By G. J. Symons, F.R.S., Secretary Royal Meteoro- 

 logical Society. (London : E. Stanford, and Simpkin 

 Marshall, and Co., 1889.) 



IN this little volume, Mr. Symons calls attention to 

 some very interesting problems connected with a 

 curious phenomenon that can frequently be studied in our 

 own well-known Lake District. It may at first sight seem 

 strange that the peculiarities of this remarkable freak of 

 Nature — for such it really seems to be — are not more 

 widely known, or that systematic and persevering inves- 

 tigations, carried on by competent observers, have not 

 long since removed all the difficulties which still stand in 

 the way of a complete explanation of the causes to which 

 the peculiar appearances are due. But it may at all 

 events be hoped that — now Mr. Symons has so patiently 

 collected and sifted the results that have been already 

 arrived at by various investigators, and added the by no 

 means unimportant facts he has himself observed — the 

 reproach to British science of an imperfectly investigated 

 and unexplained " mystery " at our very doors may at no 

 distant date be removed. 



The "history" which Mr. Symons so clearly lays before 

 us is, briefly, as follows. As far back as authentic records 

 can be obtained^ there has appeared from time to time, 

 in the south-east corner of the Derwentwater Lake, a 

 small island, or islands, which, after a certain interval 

 of time, have sunk again and disappeared. The place at 

 which this phenomenon is exhibited is approximately 

 the same at each reappearance — namely, a point off the 

 mouth of the Derwent, and about 200 yards to the west 

 of the place where the Cat Gill Beck pours its waters 

 into the lake. 



The ordinary depth of the waters of the lake at this 

 point is about 6 feet ; but the island, when it rises, ap- 

 pears a few inches above the level of the lake, and its 

 surface is perfectly green with vegetation. The island is 

 sufficiently firm to allow people to stand on it ; and on 

 one occasion a band landed on the island and played 

 a selection of airs. The area of this island has been 

 found to vary, on different occasions, from a few square 

 feet up to two acres. Sometimes, several small islets 

 have risen instead of the single one, and not infrequently 

 the island has been found to be divided by one or more 

 deep clefts. 



Careful examination shows that the island consists of a 

 peaty mass several feet in thickness, having its surface 

 covered by living specimens of Littorella lacustris. 

 Lobelia dortmattna, Isoctes lacustris, and other water- 

 plants that abound in this lake. It is also manifest 

 that the island is merely the highest part of a great 

 blister-like upheaval of the peat which here forms the 



