Dec. 29, 1887] 



NA rURE 



209 



itself disturbed let go the frog and disappeared. Happening to 

 visit the spot on the succeeding day the gentleman found the frog 

 alive in exactly the same place where it had been left by the 

 weasel, although it had been bitten through to the skull. 



At a recent meeting of the Jena Naturalists' Society, Herr 

 Stahl read a paper on the significance of those excreta of plants 

 known as raphides, i.e. crystalline needles often met with in the 

 cells in large quantity. From experiments he inferred that they 

 were a protection to plants against being eaten by animals. Many 

 animals avoid plants with raphides, or eat them reluctantly ; 

 and some animals, e.g. snail species, in eating plants that have 

 raphides select those parts that are without the crystals. Many 

 plants held for poisonous, e.g. Arum maculattitn, owe their 

 burning taste simply to the very numerous raphides, which, 

 forced out of their cells, enter the tongue and palate. The juice 

 obtained by filtration has quite a mild taste. 



We have received the Proceedings of the Academy of Natural 

 Sciences of Philadelphia, Part 2, April to August 1887. The 

 volume contains a valuable paper, by Mr. Edward Potts, pre- 

 senting " Contributions towards a Synopsis of the American 

 Forms of Fresh- water Sponges, with descriptions of those 

 named by other authors, and from all parts of the world." In 

 closing this monograph, Mr. Potts says he knows of no more 

 hopeful field of labour for a young American naturalist, seeking 

 for new worlds to conquer, than that provided by the fresh-water 

 sponges. Active workers in this field in North America have, 

 thus far, but glanced at a few streams and lakes, mostly in the 

 neighbourhoods of Buffalo, Chicago, and Philadelphia, and in 

 parts of Florida, Nova Scotia, and Newfoundland. Mr. Potts 

 has little doubt that the rest of the American continent holds 

 many rare prizes in trust for younger and better-equipped 

 explorers. 



Another important paper by Dr. B. Franke, of Leipzig, upon 

 the preparation and constitution of the hydrates of manganic 

 oxide and peroxide is contributed to the current number of the 

 Journal fiir Praktische Chemie. By the action of 100 c.c. con- 

 centrated sulphuric acid upon 8 grammes potassium per- 

 manganate, a beautiful dark reddish-brown crystalline salt was 

 obtained of the composition Mn.2(S04)3 . H2SO4 . 4H0O. When the 

 crystals of this salt were placed in asolution of soda, they were de- 

 composed with deposition of a crystalline powder. These precipi- 

 tated minute crystals were found to consist ofthe hydrate of man- 

 ganic oxide, Mn203 . HoO, and were shown to possess the consti- 



/O. .OH 



tution Mn^ pMn^ ; they were of a steel-gray colour, and 



^0/ ^OH 

 possessed. metallic lustre. On heating to a temperature exceed- 

 ing 120°, water was evolved, and black Mn^Oj re nained. 

 When, however, the reddish-brown salt was dissolved in dilute 

 sulphuric acid, a precipitate afterwards separated out, consisting of 



HO 

 pure manganous acid, MnO^. HgO, of constitution J>MnO. 



ho/ 



On rapidly filtering and washing with water, alcohol, and ether, 

 the acid was obtained as a brown powder, which on ignition be- 

 came transformed into black MnjOg. One of the most in- 

 teresting results of similar experiments with hydrochloric 

 acid, which behaves in a precisely analogous manner, is that 

 they throw considerable light upon the mode of action of hydro- 

 chloric acid upon manganese dioxide, the reaction so commonly 

 employed for the preparation of chlorine. The first action is 

 shown to consist in the formation of a chlorine substitution-pro- 

 duct of manganous acid, thus : MnOg -f 6HC1 = H^MnClg -t- 

 2H2O. This substance is, however, rapidly broken up into 

 manganous chloride, hydrochloric acid, and free chlorine : 

 HjMnClg = CI2 -f MnCla + 2HCI. A secondary action then 

 commences, the manganous chloride thus formed combines with 

 further quantities of the chlorine substitution-product to form 



manganic chloride : MnCl., -f HaMnCls = MnaClg 4- 2HCI. 

 The manganic chloride, as is well known, does not remain as 

 such, and Dr. Franke shows that, like the sulphate, it is at once 

 decomposed by water as follows : MnjClg -f 4H2O = Mn203 . 

 H2O -f 6HC1. Finally, the free hydrochloric acid decomposes 

 the crystalline hydrate with formation of stable manganous 

 chloride. It is especially important to have this reaction thus 

 thoroughly cleared up, as it is one of the earliest brought to the 

 attention of students. 



A NEW method of determining the amount of fusel oil in 

 spirituous liquors, by counting drops from an instrument named 

 a sfalagmometer, has been lately brought before the Berlin 

 Chemical Society by Herr Traube, who had previously worked 

 out such determinations with a capillarimeter, but finds the new 

 plan preferable on some accounts. The instrument is a short, 

 bent glass tube bulged at one part, into which the liquor is 

 sucked up, being previously diluted to about 20 vols, per cert. 

 The room-temperature being noted, the number of drops in a 

 given volume is counted, and then compared with the corre- 

 sponding number got at the same temperature from pure 20 per 

 cent, alcohol. A plus of about i '6 drop per cent, in the former 

 case indicates about o'l per cent, fusel oil; one of about 35 

 drops o"2 per cent, fusel oil, and so on. Even o'o5 per cent, 

 can be certainly determined, and, while the author considers this 

 arrangement quite sufficient for practice, he describes an im- 

 proved form of his method which admits of determining 0'02 

 per cent, fusel oil, as well as etheric oils, &c. In this the fusel 

 oil is first expelled from its solution by means of certain salts. 



In a recent series of experiments on the resistance of materials 

 to frost, Herr Bliimcke took the method of putting cubes of 

 various kinds of stone in distilled water, under the receiver of an 

 air-pump, and after the air was exhausted and the cube saturated 

 with liquid, exposing the latter to a freezing mixture. He finds 

 that a material is more resistant the less the weight of particles 

 it loses in a given number of freezings. The results corre- 

 sponded pretty much to experience. Besides the well-known 

 visible phenomena of weathering, there is, even in the first action 

 of frost, a loss of extremely fine particles, not perceptible in the 

 material itself The appearance of the visible phenomena occurs 

 sooner the more water the stone has taken up. The mode of 

 working has a not unimportant influence on the resistance of 

 materials. 



At the monthly meeting of the Linnean Society 'of Ne.w 

 South Wales, held October 26, Dr. Oscar Katz read a paper 

 on three new kinds of phosphorescent Bacteria, in addition to 

 three already recorded by the author at the meeting of last 

 June : (i) Bacillus argenteo-phosphorescens liquefaciens, ob- 

 tained from sea-water at Bondi ; its cultures, liquefying 

 gelatine, emit in the dark a silvery light, which, however, is 

 the weakest of the six kinds hitherto found ; (2) Bacillus 

 argenteo-phosphorescens II., derived from a luminous piece of a 

 small squid (Loligo), and, at the same time, from luminous 

 pieces of the Sydney Garfish {Hemirha/nphus iniertnedius. 

 Cant., H. melanochir, Cuv. and Val.); (3) Bacillus argenteo- 

 phosphorescens HI., from the squid already mentioned. Neither 

 of the latter micro-organisms causes liquefaction of the gelatine. 

 They give off in the dark a handsome silver light, much more 

 intense than that of the first-mentioned, but resembling that of 

 the previously-exhibited Bacillus argenteo-phosphorescens (now 

 to be designated I.). From this latter Nos. 11. and HI. dis- 

 tinctly differ. Fuller details about all these luminous Bacteria 

 will be forthcoming shortly. 



During his last journey to the Amdo, M. Potanin discovered 

 an interesting manuscript containing a Tibetan version of the 

 Mongolian epics of Hesser-Khan. Speaking of this discovery, 

 Prof Vasilieff has lately expressed his belief that travellers might, 

 if they tried, find many valualjle manuscripts in Eastern Turkistan 



