July (3, 1893] 



NA TURE 



263 



strong and W. P. Wyane. By displacing the ainido-^roiip in a 

 naplithylamine derivative by SH and oxidising the resulting 

 ihloderivative, asulphonic group enters the position previously 

 occupie.l by the amidogen. By means of this reaction the 

 authors have prepired and characterised the I : i', I : 2 and 



1 : 4 naphthilenedisulphonic acidi ; nine out of the theoretically 

 possible ten of these isomerides are hence now known. The 



2 : 2' : 3' naphthalenetrisulphonic acid has been prepared by a 

 similar method. The corresponding sulphonic chlorides and 

 other derivatives of the above acids are also described. — Supple- 

 mentary notes on madder colouring matters, by E. Schunck 

 and L -Marchlewski. In 1853 Schunck obtained from madder 

 a yellow colouring matter which he termed rubiadin ; it is now 

 shown that madder contains a glucoside of rubiadin, having the 

 composition CjiH^jOj. It yields a pentacetyl derivative, and 

 on hydrolysis is converted into rubiadin and dextrose. C2iH.,Q0a 

 + H2O = CjjHjdOj + CjHi^Og. — The conititution of rubia- 

 din glucosiile and of rubiadin, by L. Marchlewski. The author 

 proposes a formula for rubiadin glucoside, and notes that on 

 heating a mitlure of symmetrical met^dihydroxybenzoic acid, 

 paramethylbenzoic acid, and sulphuric acid, he has obtained a 

 substance isomeric with and closely resembling rubiadin, but 



1 melting at a lower temperature. 



I Physical Society, June 23.— Prof. A. W. Riicker, F.R.S., 



I President, in the chair. — Mr. F. H. Nalder exhibited a bridge 



land commutator for comparing resistances by Prof. Carey 



Foster's method, the chief features of which are simplicity, 



coiiipactness, long range, and great accuracy. The commuta- 



,lijn of the colli to be compared is effected by mercury cups, the 



eight holes necessary for this purpose being arranged in a circle. 



An ebonite disc carrying the four connectors is mounted on a 



spindle in the middle of the circle, andthe positions of the coilsare 



interchanged by rotating the disc through 180°. A large range 



is secured by providing a number of interchangeable bridge 



wires, and a fine adjustment for the galvanometer key enables 



great accuracy to be attained. — Mr. W. R. Pidgeon and Mr. T- 



IWimshurst each read a paper on an influence machine, and e"x- 



ihibited their machines in action. In designing his machine, 



iMr. Piilgeon has endeavoured — first, to make the capacity of 



ieach sector large when being charged, and small when being 



jWischarged ; second, 10 prevent leakage from sector to sector 



fcis they enter or leave the diff.^rent fields of induction ; and 



khird, to increase the capacity of the machine by making the 



Sectors large and numerous. The first object is attained 



|by arranging fixed inductors of oppodte sign to the sectors 



^ear the charging points, and of "the same sign near the 



places of discharge. Objects 2 and 3 are secured by embedding 



(he sectors in wax, run in channels m the ebonite discs which 



form the plates of the machinf, and c.irrying wires from each 



kecior through the ebonite, each wire terminating in a knob. 



In this way the sectors can be placed much nearer together than 



)iherwi-ie without sparking back. By setting the sectors skew 



viih the radius they are caused to enter the electric fields more 



;radually, consequently the potential difference between aija- 



:ent sectors is kept comparatively small. Experiment showed 



hat the use of the stationary inductors at the charging points 



ncreased the output threefold, and as compared with an 



irdinary Wimshurst, the output fora given area of plate passing 



he con luctors was as 5-6:1. The recovery of the machine 



ifter a spark had occurred was particularly rapid. Mr. Wims- 



iurst'snew machine c msists of two glass discs 3 feet 5 inches 



iiameter, mounted about X apart on the same spindle. Both 



»lales turn in the same direction. Between the discs are fixed 



bur vertical glass slips over 4 feet Ion.', two on each side, and 



' ach covering about gih of a disc. Each slip carries a tinfoil 



]ductor, which has a brush touching lightly on the inside of the 



' djacent disc on its leading edge. Colleciing and neutralising 



irushes touch the outsides of the discs, and the lew metallic 



ectors attached thereto. An account of some experiments 



lade to determine the efficiency of the machine was given. The 



uthor also showed that when all the circuits of the machine 



rere broken, it still continued to excite itself freely, and sparked 



om the discs to the bands when brought near. In a written 



lOMimunication, Prof. O. Lodge said his assistant, Mr. E. E. 



jlobinson, constructed a machine on lines similar to Mr. 



i'idgeon's a few months ago, and had now a large one nearly 



pmpleted. Mr. Robinson's fixed inductors are carried on a 



liird plate fixed between the two movable ones. The sectors 



ire quite small, and neither they nor the inductors are 



mbedded. On close circuit the macliine gives a large 



i NO. 1237, VOL. 48] 



current (ruS^ifjf ampere), and on open circuit exceedingly 

 high potentials. In Dr. Lodge's opinion, Mr. Pidgeon 

 attaches too much importance to his sectors and their shape. 

 Mr. J. Gray wrote to say that stationary inductors enclosed in 

 insulating material would probably give trouble at high voltages, 

 because of the surface of the insulator becoming charged with 

 electricity of opposite sign to that on the inductor. lie sug- 

 gested that this might explain why Mr. Pidgeon could not ob- 

 tain very long sparks. Prof. C. V. Boys inquired as to hjwfar 

 the wax made insulating union with the ebonite, for if good, 

 glass might possibly be used instead of ebonite. He greatly 

 appreciated the design of Mr. Pidgeon's machine. After some 

 remarks by the president on the great advances which had been 

 made, Mr. Pidgeon replied, and Mr. Wmishiirst tried some 

 further experiments with a small experimental machine.— A 

 paper on a new volumemometer, by Mr. J. E. Myers, 

 describing the developed form of Prof. Stroud's instrument, 

 was, in the absence of the author, taken as read. — Mr. R. W. 

 Paul exhibited a compact form of sulphuric acid voltameter of 

 small resistance. The voltameter is a modification of a pattern 

 designed at the Central Institution, in which the rate of dec mi- 

 position is determined from the time required to fill a bulb made 

 in the stem of a thistle funnel. He also showed a handy form 

 of Daniell cell devised by Prof. Barrett. When not in use, the 

 porous pot containing the zinc is removed from the copper sul- 

 phate solution and placed in a vessel containing zincsulphite or 

 sulphuric acid. A paper on long-distance telephony, by Prof. 

 J. Perry, F. R. S., assisted by II. A. Beeston, was read by 

 Prof. Perry. The case of a line of infinite length, hiving re- 

 sistance capacity, self-induction, and leakage, is taken up, and 

 the state of a signal as it gets further and further away fro.-n the 

 origin is considered. Taking the shrillest and gravest notes of 

 the human voice to have frequencies of about 950 and 95 re- 

 spectively, the distance from the origin at which the ratio of 

 the amplitudes of these high and low frequency currents is 

 lessened by i//«:h of itself, has been deter.nined when m = 4 

 for different values of leakage and self-induction ; and un ler 

 similar conditions the distances at which the relative phase of 

 the two currents become altered by i/«th of the periojic tim; 

 of the most rapid one, have been worked oat for « = 6. The 

 results are given in the form of tables, from which it appe irs 

 that if there was no self-induction, increasing the leakage in- 

 creases the distance to which we can telephone, whilst if there 

 was no leakage increasing the self-induction increases the dis- 

 tance. When self-induction and leakage are not toi great, in- 

 creasing either increases the distance, and for particular values 

 the distances become very large. At the end of the paper 

 tables of general application are given, from which the limiting 

 distances for any line can be readily found by multiplying the 

 numbers by simple functions of the constants of the line. VIr. 

 Blakesley said tint some ten years ago he discussed the subject, 

 when capacity and resistance were alone considered, and now 

 pointed out that when self-induction and leakage were intro- 

 duced the equations were still of the same form. He also 

 suggested how terminal conditions on lines of finite length might 

 be easily taken into consideration. Prof. Perry, in reply, said 

 the introduction of self-induction and leakage rendered the 

 calculations very laborious, and that the terminal conditions 

 were much more complicated than Mr. Blakesley supposed. 



Zoological Society, June 20. -Sir William II. Flower, 

 K.C.B., F.R.S., President, in the Chair.— The Secretary 

 exhibited and made remarks on two eggs of the Cape Culy 

 {Coliiis capensis) laid in the Society's Gardens. — A head of a 

 rhinoceros from Northern Somali-land was shown by Mr. 

 Walter Rothschild ; also a Caspian seal, believed to be the only 

 specimen of this seal in England ; and a series of skins of parrots 

 of the genus Cyanorhamphus from New Zealand and oher 

 islands of the South Pacific. Mr. Rothschild proposed to refer 

 the specimens of this group from the Auckland Islands to a new 

 species to be called C forbed. — Other objects exhibited and 

 remarked upon were a specimen of the foot of a calf, in which 

 there were three toes springing from a single cannon-bone, by 

 Mr. W. Bateson, some teeth of a ray {Myliobaiis) from the 

 Lower Tertiaries of Egypt, remarkable for their enormous size, 

 by Mr. A. Smith-Woodward, and a fragmentary skull of a 

 lemuroid mammal from south-east Madagascar with very 

 remarkable characters, by Dr. Forsyth-Major. — A communi- 

 cation was read from Messrs. Hamilton II. Druce and G. T. 

 Bethune-Baker, containing a monograph of the butterflies of 

 the genus Thysonolis. This included a revision of the synonomy 



