442 



NA TURE 



[February i i, 1909 



obtained from either batteries or the central station supply. 

 Both direct current and alternating currents can be used, 

 but in the latter case a rectifier must be placed in circuit. 



Messages can be sent to practically any number of tele- 

 writers from one transmitter, thus assuring the same 

 message being received simultaneously on the various 

 receivers. 



The Postmaster-General has granted a licence for twenty- 

 one years to the Telewriter Syndicate, and after 191 1, 

 when the National Telephone Company's licence expires' 

 the Telewriter Syndicate will operate its own system and 

 establish telewriter exchanges, paying royalties for the 

 same. These lines will be independent of the Post Office 

 telephones, but will be leased from the Post Office, and 

 telephonic communication in addition is to be a sine qua 

 lion on all these lines. 



At present the telewriter is established chiefly on private 

 lines, and is working satisfactorily in many 'large ware- 

 houses, stores, and offices, but messages and 'sketches have 

 been successfully sent from London to Manchester over the 

 Post Office telephone trunk lines, which were used, by 

 permission, for the experiment. Arrangements and special 

 instruments are now being made with "the view of scndin'^ 

 similar messages over the existing trunk telephone line 

 from London to Paris. 



SOME ENTOMOLOGICAL PAPERS. 

 ^MONG recent papers on entomology in serials with 

 which we have been favoured, special reference may 

 be made to one by Mr. P. H. Calvert on the dragon-flies 

 (Odonata) of Mexico and Central America, published in 

 the Proceedings of the Academy of Natural Sciences of 

 I hiladclphia for October last. This paper, which is mainly 

 based on the article by the same author in the BioJogia 

 Ccnirah Americana, forms an important contribution to 

 the study of insect-faunas gencrallv, and treats in «reat 

 detail of the relationships of the gro'up under considermion 

 It IS assumed— and probably correctly— that the adult 

 insects do not wander far from the haunts of their aquatic 

 larva:, but until this is definitely ascertained the generalisa- 

 tions, as the author points out, must be regarded as more 

 or less provisional. 



To the sixth part of vol. v. of the Annals of the South 

 African Museum Mr. L. Peringuev contributes a seventh 

 instalment of his account of the coleopterous fauna of the 

 country, dealing in this instance with considerably more 

 than one hundred species and several genera described as 

 new. The paper, which is illustrated by two monochrome 

 plates, IS of a purely ta.xonomic character, with the descrip- 

 tions in Latin. 



An addition to our knowledge of the aphides ofTapan 

 IS furnished by Mr. G. Okajima in vol. viii.. No. i of 

 the_ Bulletin of the College of Agriculture of the Imperial 

 University of Tokio. This paper is devoted to the descrip- 

 tion of three new species of Trichosiphum, a genus founded 

 so recently as 190b for the reception of another Japanese 

 representative of the group. To the same issue this author 

 contributes a more generally interesting paper, namely, 

 one on the structure of the aphid antenna. These antenna: 

 ^■"f composed of not more than six joints, of which the 

 third and later ones (especially the third) usually bear 

 sensory pits. For their distal portion the ' name 



flagellum is adopted. It is found that, as regards 

 minor characters, the antenna; present specific differences 

 which harmonise well with the various groups into which 

 the family has been divided. 



In a third paper in the serial last cited Mr. T. Miyake 

 gives a list of Japanese Panerpida;, together with des'crip- 

 tions_ of ten new species of the tvpc-genus, .-ill of which 

 are illustrated in an accompanying plate. All the new 

 species, which display the general type of colouring 

 characteristic of these elegant insects, agree with the other 

 .Japanese members of the group in regard to a peculiarity 

 in one part of the wing-venation. 



Under the title of Indian Forest Memoirs, the Govern- 

 ment of India has commenced the issue of a new quarto 

 seri.nl, intended for the publication of the more important 

 results of the investigations of the Imperial Forest Re- 

 search Institute. The publication of Indian Forest 

 NO. 2050, VOL. 79] 



Records is to be continued for minor papers, and the two 

 serials are to constitute the Forest Zoology Series. The 

 first part of the Memoirs is devoted to an account, by 

 Mr. E. P. Stabbing, of some undescribed Scolytida; of 

 economic importance from the Indian region. Until 

 recently, very little was known with regard to the Indian 

 representatives of this group of bark-boring beetles, and 

 scarcely anything of their life-histories and food-plants. 

 It is now ascertained that the Scolytid^e are of very con- 

 siderable importance to the Indian forester, this being 

 specially the case as regards the great coniferous forests 

 of the Himalaya. Other species, referable to the genus 

 Sphoerotrypes, are, however, detrimental to the sal-forests 

 and other broad-leaved timber-trees. In the present 

 memoir Mr. Stebbing describes three new species of the 

 last-named genus, five of Polygraphus, and two of 

 Dryocetes. Among the species of Spha:rotrvpes, one, 

 S. assamcnsis, infests the sal-timber of Assam and eastern 

 Bengal, and a second, S. quercyi, the oaks of Kumaun. 



The Angolese tiger-beetles of the subfamily Cicindelinae 

 form the subject of an article by Messrs. F. Creighton 

 Wellman and W. Horn in the Proceedings of the Academy 

 of Natural Sciences of Philadelphia for November, 1908. 

 .Angola, it appears, is divisible into three distinct physical 

 regions, namely, lowlands, mountainous slopes, and high 

 plateau, the climate of the second of these being cooler 

 and moister than that of the first, although not to the 

 same degree as the third. Each of these areas has its 

 own special tiger-beetle fauna, that of the middle zone 

 possessing the largest number of species. 



In this place reference may be made to investigations 

 undertaken in Cornell University by Mr. B. H. Guilbeau, 

 of which the results are published in the American 

 Naturalist for December, 1908, as to the mode in which 

 the " cuckoo-spit insects " (Cercopida;) secrete the foam 

 in which they are enveloped. By cleansing the nymphs 

 from the investing froth, it has been ascertained that 

 the fluid issues from the anal aperture, and is converted 

 into froth by periodical removals of the tip of the abdo- 

 men, which is re-introduced holding each time a bubble 

 of air. Viscosity is imparted to the fluid by the secretion 

 of the glands of Batelli. 



In conclusion, brief mention may be made of an interest- 

 ing article, by Mr. A. H. Swinton, on the vocal and 

 instrumental music of insects, the first instalment of which 

 appears in the January number of the Zoologist. 



THE CHARGES ON IONS.' 

 'T'HE ratio of the charges of ions in liquids to those pro- 

 ■*• duced by various methods in gases is a factor that 

 enters into many investigations connected with molecular 

 theories, so that it is of importance that the connection 

 between these charges should be investigated by some 

 accurate method. 



The simple relations that hold between the charges of 

 ions in liquids can be easily deduced from the theory of 

 electrolytic conduction. It follows immediately from deter- 

 minations of the electrochemical equivalents that the charge 

 on any ion in a liquid is either equal to that on a hydrogen 

 atom or an exact multiple of it. No method has been 

 devised for determining this charge directly, but the value 

 of nxe, the product of the number of molecules in a cubic 

 centimetre of a gas at standard pressure and temperature 

 (15° C.) and the charge e expressed in electrostatic unts, is 

 accurately known, and is approximately 1-23x10'°. 



In gases it is possible to obtain a rough estimate of 

 the charge on an ion. The method of determining the 

 charge, which requires a cloud to be formed in the gas, 

 was given by the present writer (Proc. Camb. Phil. Soc, 

 vol. ix., part v., February, 1897), and was first applied 

 to the ions in newly prepared gases. The same principle 

 was subsequently used by Sir J. J. Thomson and Prof. 

 H. A. Wilson in determining the charges on ions pro- 

 duced by Rontgen rays, ultra-violet light, and radio-active 

 substances (J. J. Thomson, " Conduction of Electricity 

 through Gases "). The numbers obtained for e in electro- 

 static units range from 3x10-'° to gxio-'°, but an 



I Based upon papers by Pmf. J. S. Townsend, F.R.S., and Mr. Haselfoot, 

 communicated to the Royal Society January and Novtraber, 190S. 



