586 



NA TURE 



\Oct. 2 1, 1880 



CH2CI— CH(OH)— CH2CI 

 was produced; this was oxidised by potassium dichromate 

 and sulphuric acid, to dichloracetone, 



CH2CI— CO— CH3CI, 

 which, when acted on by concentrated hydrocyanic acid, 

 yielded dichloracetone cyanhydrin, 

 ./CN 



r\cH.,cr 



CH.,C1— c< 



OH 

 The acid corresponding to this cyanhydrin having been 

 produced by saponifying with hydrochloric acid, the 

 sodium salt of this acid, viz., 



'-"-*-'~y\cHxi' 



OH 

 was treated with potassium cyanide, whereby a dicyanide, 



^"- '■^ |\CH,.CN 



OH 



was produced. When decomposed by hydrochloric acid, 



this dicyanide yielded citric acid, in all respects identical 



with that obtained from the lemon and other fruits. The 



generally accepted structural formula for citric acid, viz., 



,/CO.,H 



rXCH'.COoH 



CH„.CO,H— C< 



OH 



is confirmed by the synthesis of Grimaux and Adam. 

 Glycerin may be prepared from trichlorhydrin, 



CHXl-CHCl— CHjCl, 

 which is itself obtained by the action of chlorine in day- 

 light on propylenic chloride, 



CH3— CHCl— CHXl, 

 one of the products of the chlorination of propylene, 

 C3H1;. Finally this hydrocarbon, propylene, may be 

 produced by passing a mixture of carbon monoxide and 

 marsh gas through a red-hot tube. Inasmuch as carbon 

 monoxide and marsh gas are easily built up from carbon, 

 hydrogen, and oxygen, the synthesis of citric acid from 

 these three elements is now an accomplished fact. 



In connection with this synthesis, it is worthy of remark 

 that in the last number of the Berlin Berh/ite, Kekuld 

 announces that he has been working at the same subject, 

 but by a totally different method. Kekule's work is not 

 sufficiently advanced for him to say positively that his 

 method of synthesis is successful, but he feels justified in 

 saying that very probably the process adopted by him 

 has resulted in the formation of citric acid. 



M. M. P. M. 



PLANTS FROM LAKE NYASSA AND LAKE 



TANGANYIKA 

 ■]\/TR. THOMSON, who has recentlv returned from the 

 -'■''-»- expedition of the Royal Geographical Society to 

 Central Africa, has brought to Kew a considerable col- 

 lection of plants from the plateaux round Lake Nyassa 

 and Lake Tanganyika. The plants from an elevation of 

 6,000 to 8,000 feet above sea-level contain a large pro- 

 portion of Cape and characteristically temperate types. 

 Amongst the former are the well-known Dicrama (Spa- 

 nt.vis) pcndula, Scilla rii^uii/olia, Buphanc toxicaria (the 

 great poison bulb of Natal and the Transvaal), a fine 

 Moraa with a long tube and bright purple flowers as large 

 as those of Iris Jtstidissima, a Gladiolus, a Pelaygoniitm, 

 more than one species of Giiidia and Helichrysiim, and 

 a proteaceous shrub (probably Faurca, which extends to 

 Abyssynia) with large heads of flowers. Of characteris- 

 tically temperate types there are species of Geranium, 

 Aumcx, Ccras/ium, Coalamiiilha, SiXidd. Scabiosa, perhaps 



identical with our European and English S. Columbaria. 

 Upon the plateaux below 6,000 ieet the vegetation 

 assumes a sub-tropical character. Here he met with a 

 tree-fern of the genus Cyathca, Agauria salici/olia, Hook, 

 fil, an ericaceous shrub common to Bourbon, Madagas- 

 car, and the Cameroons, representatives of ji'Iimulopsis, 

 Hibiscus, Clematis, Pliyllanthus, Gerbera, Siiiithia, Aca- 

 lyplia, Pen/as, Thunbergia, Buchnera, Striga, a shrubby 

 Spermacoce, a curious Loranthus with broad leaves 

 and tubular flowers densely clothed with yellow hairs, 

 Hypoxis Villosa, several fine Dombeyas, Vernonias, 

 and Combretums, a genus of Hedysareee with flowers in 

 heads like those of the hop, and a curious broad-leaved 

 Euphorbia, with very large hand-like glands to the in- 

 volucre. The specimens are well selected and excellently 

 dried. It is probable that nearly all of them are in a 

 condition in which their botanical position can be settled, 

 and that although upon a hasty glance there do not seem 

 to be any strongly-marked new generic . types, a good 

 many of the species will prove new to science. The 

 marked northern extension of the Cape flora at compara- 

 tively high elevations in Central Africa is a fact of im- 

 portance. It quite supports the theory- that that flora 

 is of great antiquity, and that what exists of it at the 

 Cape is only a survival from a period when it was probably 

 far more extensively diffused, though perhaps less highly 

 specialised. It is much to be desired that travellers in 

 Central Africa would do all in their power to collect dried 

 specimens of the vegetation of elevations above 6,000 feet. 



GRAHAM BELL'S EXPERIMENTS IN 

 BINAURAL AUDITION 

 pROF. GRAHAM BELL has published in the American 

 ■'■ (quarterly) Journal of Otology a memoir on some 

 experiments relating to bmaural audition, read by him 

 last autumn at the session of the American Association 

 for the Advancement of Science. Some of his obser- 

 vations confirm the work of previous observers, but are 

 of additional value in affording a more systematic examina- 

 tion of some of the phenomena than has hitherto been 

 attempted. The following summary of the results obtained 

 by him will therefore be of some interest. 



When we close one ear and listen to sounds through 

 the other only, there seems to be a onesidedness about 

 them, as there is about objects perceived by one eye. 

 When both ears are employed simultaneously a sort of 

 stereoscopic effect of audition is perceived. Sounds 

 assume a "solidity" which was not perceptible so long 

 as one ear alone was employed. The difference between 

 monaural and binaural audition is especially well marked 

 when we attempt to decide by ear the locality of a par- 

 ticular sound. Whatever power a single ear may possess 

 of determining the direction of a source of sound, both 

 ears are certainly much more effective for this purpose. 



The following experiment, designed to produce arti- 

 ficially the stereophonic phenomena of binaural audition, 

 was therefore devised by Prof. Bell while in this country 

 in 1878. p'our telephones were arranged, as in the figure. 

 The telephones a and b in one room ; c and d in another. 

 The mouthpieces of A and B were turned away from one 

 another like the auricles of a person's ears, and the 

 diaphragms were about as far apart as the tympana of 

 the two ears. The expectation was that a person holding 

 C and D to his ears should not simply hear speech when 

 any one was talking near A and B, but that he should be 

 able to perceive the direction of the speaker's voice rela- 

 tively to A and B. In fact, the listener's ears were, as it 

 were, electrically prolonged to A and B respectively. The 

 sensations produced were decidedly novel; but not exactly 

 such as had been expected. Using various sources of 

 sound — speaking, ringing a loud dinner-bell in various 

 parts of the room, &c. — it was found that the location of 

 the sound could be determined to a limited extent. The 



