July 5, 1894] 



NATURE 



229 



duced. Both are in electrical comtnunicalion, and in separate 

 apartments, so that the direct sounds of the taps may not in- 

 terrupt the listener, whose duty it is to detect flaws. In apply- 

 ing the system, one operator places the telephone to his ear, and 

 while the sounds produced by the taps are normal he does 

 nothing. Directly a false sound, which is distinguishable from 

 the normal sound, is heard, he signals for the spot to be marked, 

 and by this means is able, not only to detect a lliw, but to fix its 

 locality. 



The current number of the Johns Hopkins University 

 (U.S.A.) Circular contains a preliminary note, by Edwin F. 

 Korthrup, on a new method of obtaining the specific inductive 

 capacity of solids under either slowly or rapidly changing fields. 

 It is of great importance in connection with Maxwell's electro- 

 magnetic theory of light that, since the refractive index for most 

 substances has only been measured for very short waves, the 

 specific inductive capacity be measured under such circum- 

 stances that the field of force alternates with such rapidity as to 

 produce waves comparable in length to the waves with which 

 the refractive index is determined. The apparatus employed 

 by the author consists of three heavy brass plates, fastened 

 parallel to each other, and separated by about three inches. 

 Each plate is held in position by four insulating strips of 

 ebonite, through the ends of which pass four iron rods with 

 a screw-thread cut upon their whole length. To the centre of 

 each of the two outside plates, and perpendicular to the plate, 

 is fastened a brass tube. A rod, half of which is of ebonite, 

 moves in this tube and carries at its end a thin plane plate of 

 glass, the surface of which is coated with metal foil. These 

 small movable plates are as nearly as possible parallel to the 

 large plates, and their position is given by a vernier attached 

 to the ebonite rods. The two outside plates are connected by a 

 metal rod which carries a metal ball, .\nother ball, nearly 

 opposite the first, is fixed by a short metal pin to the middle plate 

 so that the distance between the balls can be adjusted. In 

 employing the apparatus to measure specific inductive capacity 

 with rapidly varying fields, the following arrangement is used. 

 The two outside plates and one terminal of a large induction 

 coil being connected to eatth, the other terminal of the coil is 

 connected to the middle plate. When the coil works, sparks 

 pass between the balls, and oscillations are set up. The lines of 

 force, when air only is the dielectric, divide evenly between the 

 plates, and in the region of the small plates the field may be 

 considered as uniform ; hence if these plates are at equal 

 distances from the centre plate, they will always remain at the 

 same potential. If, however, a plate of some other dieleclric is 

 placed between the centre plate and one of the movable plates, 

 in order that the two small plates may remain at the same poten. 

 lial, they will have to be placed at- unequal distances from the 

 centre plate, and from their relative positions the specific inductive 

 capacity can be deduced. In order to " weed " out the eflfecls 

 of the slow changes of potential due to the charge and discharge 

 of the coil, the two small plates are connected to the primary of 

 a small transformer, the secondary of which contains a spark- 

 gap. In this way the effects due to the slow changes are 

 eliminated, ;ince the rate of variation of the induction in the 

 transformer, due to these slow changes, is not sufficient to raise 

 the potential in the secondary to the 300 volts or more required 

 to break down the dielectric in the spark-gap. 



Studies of the eastern Yucca Moth {Pionulia yuccasella) and 

 its importance in Yucca pollination, have, from time to time, 

 been recorded in reports of the Missouri Botanical Garden. In 

 a recent report, Mr. J. C. Whitten describes observations which 

 complete the knowledge of the life-history of this interesting 

 insect. The observations refer to the time when the larva 

 ceases feeding in the capsule, until it is encased in its under- 

 NO. 1288, Vf L. 50] 



ground cocoon, when, the following spring, it is to change to the 

 pupa state. It was found that the larvae made their escape from 

 the capsules of Yucca filamei:tosti,3.aA entered the soil during 

 rainy weather, when the ground was softened, and consequently 

 easily penetrable. They did this either during the daytime or at 

 night, and not exclusively toward the end of the night, as Prof. 

 Riley had predicted. The larvce descended to the ground both 

 by use of a thread and by crawling. 



A CATALOGUE of works on entomology, being No. 26 of 

 Bibliotheca Entomologica, has been issued by Herr Felix L. 

 Dames, Berlin, Koch-Strasse 3. 



We have received from the Revenue and Agricultural 

 Department of the Government of India a copy of the Returns 

 of Agricultural Statistics of British India and the Native Slate 

 of Mysore for 1892-93. 



The May number of the Journal of the Jersey Biological 

 Station {Jour, of Mar. Zool. and Micros., edited by James 

 Hornell, vol. i. No. 3, 1894) contains several original con- 

 tributions by the editor, in one of which is given an interesting 

 I account of the variability of the opercular filaments in Serpula 

 i pectina'.a. Elementary and picturesque descriptions are also 

 ■ given of the metamorphoses of the Crustacea Squilla damareslii 

 I and Si-yllarui arclus, and of the structure of anemone^. The 

 I number is illustrated by several autographic plates and wood- 

 cuts, and contains a frontispiece giving a photographic view of 

 the aquarium of the laboratory, which would seem, froin the 

 editorial report, to be making well-merited progress. 



The special articles, official reports, notes, communications, 

 and reviews in part ii. of vol. v. of the Journal of the Roya 



I Agricultural Society, issued on June 30, make up a number 

 replete with information. The first two meetings of the Society — 

 Oxford 1839 and Cambridge 1S40— are described by Mr. Ernest 



1 Clarke. Profs. J. McFadyean and G. T. Brown write on the 

 prevalence of anthrax in Great Britain, Mr. Joseph Darby on 



j irrigation and the storage of water for agricultural purposes, and 

 Dr. Fream on some minor rural industries. Among the official 

 reports, we note one by Dr. J. A.. Voelcker on aubury, club- 

 root, or finger-and-toe, in turnips. Dr. J. M. H. Munro writes 

 on sewage disposal and river pollution, and Lord Egerton of 

 Tatton describes the Tewfikieh College of Agriculture, Egypt. 



The makers of a very neat little camera, Messrs. R. 

 and J. Beck, have just send us a copy of the " Frena I tandbook," 

 in which the inventor says practically all there can be said with 

 regard to the description, method of use, manipulation, cic, 

 connected with this instrument. For the benefit of "some 

 future philologist" who may at some time be in doubt as to the 

 derivation of the word " Frena," an etymological note informs 

 us that it is derived from " faro " and " crena," the former being 

 thenameof the well-known game of cards.and the latter meaning 

 a notch ; the instrument automatically discharging one film 

 after another like & faro-box, and doing this by means of notches. 

 In this camera notched films are used, being thin and 

 stiff sheets of transparent cellulose film, and as many as forty 

 can be carried in the holder at the same time. With regard to 

 some of the technical data of the No. 2, quarter-plate, size, the 

 lens is an "autograph" rapid rectilinear of focal length 5* 

 inches, normal aperture F- 11, and covers a 3 X4t inch film ; 

 the dimensions of the case are 1 1 1 x 54 x 4.^ inches, and «hen 

 filled with forty films the apparatus weighs four pounds. 

 Among many of the advantages of this camera m.iy be men- 

 tioned the arrangement by which the films may be tilted, thus 

 providing a neat and easily worked form of swing-back. After 

 the introduction, the author of this handbook gives a very brief 

 and concise summary of the outline of operations necessary for 

 the veriest beginner, printing them in red ink. This, however, 



