yune'^. 1876] 



NATURE 



M3 



the column, and consequently the number of the striae, depends 

 mainly upon the resistance of the tube, the duration of the entire 

 current, and to a certain extent upon the amount of the battery 

 surface exposed, and in that sense upon the strength of the cur- 

 rent. The velocity of the proper motion, other circumstances 

 being the same, depends upon the number of cells employed. 



The paper next gave descriptions of the phenomena exhibited 

 by several tubes ; and drawings illustrative of the descriptions 

 were added. 



The following are some of the general conclusions to which 

 the experiments detailed in the paper seem to lead : — 



I. The thin flake-like stria;, when sharp and distinct in their 

 appearance, either are short-lived or have very slow proper 

 motion, or both. 



2 The apparent irregularity in the distribution of such strias 

 during even a single discharge of the coil, is due, not to any 

 actual irregularity in their arrangement, bat to their unequal 

 duration, and to the various periods at which they are renewed. 

 The striae are, in fact, arranged at regular intervals throughout 

 the entire column. The fluttering appearance usually noticeable 

 is occasioned by slight variations in position of the elementary 

 strife at successive discharges of the coil. With a view to divest- 

 ing the coil discharge of this irregular character, as well as for 

 other purposes, I devised two different forn»s of contact break- 

 ers (one of which is described in the Royal Society's Proceed- 

 ings, 1874) ; but I postpone a description of the second, as 

 well as of the experiments arising from its use, to another 

 occasion. 



3. The proper motion of the elementary striae is that which 

 appertains to them during a single discharge of the coil. This 

 is always directed from the positive towards the negative ter- 

 minal. Its velocity varies generally within very narrow limits. 

 It is greater the greater the number of coils employed. In some 

 tubes it may be seen to diminish towards the close of the dis- 

 charge, and even in rare instances alternately to increase and to 

 diminish during a single discharge. 



4. Flocculent striae, such as are usually seen in carbonic acid 

 tubes, are a compound phenomenon. They are due to a suc- 

 cession of short-lived elementary striae, which are regularly re- 

 newed. The positions at which they are renewed determine the 

 apparent proper motion of the elementary striae. If they are 

 constantly renewed at the same positions in the tube, the floccu- 

 lent striae will appear to have no proper motion, and to remain 

 steady. If they are renewed at positions nearer and nearer to 

 the positive terminal, the proper motion will be the same as that 

 of the elementary striae ; if they are renewed at positions further 

 and further from the positive terminal, the proper motion will 

 be reversed. 



5. The velocity of proper motion varies, other circumstances 

 being the same, with the diameter of the tube. This was 

 notably exemplified in the conical tube. In tubes constructed 

 for spectrum analysis the capillary part shows very slight, while 

 the more open parts often show considerable proper motion. 



6. Speaking generally, the discharge lasts longer in narrow 

 than in wide tubes. In spectrum tubes the capillary part gives 

 in the mirror an image extending far beyond that due to the 

 wider parts. 



7. The coil discharge appears, in the earlier part of its deve- 

 lopm.ent at least, to be subject to great fluctuations in extent. 

 In all cases there is a strone outburst at first. This, although 

 sometimes appearing as a bright line, is always, I believe, really 

 stratified. Immediately after this there follows a very rapid 

 shortenir.g of tlie column. The extent of this shortening varies 

 with circumstances ; but when, as is often the case, it reaches 

 far down towards the positive terminal, a corresponding diminu- 

 tion of intensity is perceptible in the negative glow. The column 

 of striae, after rising again, is often subject to similar fluctuations. 

 These, which are sometimes four or five in number, are succes- 

 sively of less and less extent, and reach only a short distance 

 down the column or striae. The rifts due to these fluctuations 

 then disappear, and the striae either continue without interrup- 

 tion, or follow broken at irregular intervals, until the close of the 

 discharge. 



8. The effect of the proper motion, taken by itself, is to 

 shorten the column of striae. But, as we have seen, the striae 

 are in many cases renewed from time to time. In regard to this 

 point, the head of the column presents the most instructive 

 features. After the cessation of these rifts, the general appear- 

 ance of the field is that of a series of diagonal lines commencing 

 at successive points which form the bounding limit of the column 

 at successive instants of time. If the points are situated in a 



horizontal line, the striae are renewed at regular intervals at the 

 same place ; and the length of the column is maintained by a 

 periodic renewal of striae, a new one appearing at the head 01 

 the column as soon as its predecessor has passed over one dark 

 interval. If the boundary of the illuminated field rises, the 

 length of the column increases ; if it descends, the column 

 shortens. In every case, however, the growth of the column 

 takes place by regular and successive steps, and not irregularly. 

 The intervals of the new striae from one another and from the 

 old ones are the same as those of the old ones from one another. 



9. The principal influence of a change in the number of cells 

 used appears to consist in altering the velocity of proper motion. 

 A change in the amount of battery-surface exposed produces a 

 corresponding change in the duration of the entire discharge, as 

 well as apparently in the development of some of the minor 

 details of the striae. 



10. When the proper motion of the elementary striae exceeds 

 a certain amount, the striae .appear to the eye to be blended into 

 one solid column of light, and all trace of stratification is lost. 

 When this is the case the mirror will often disentangle the indi- 

 vidual strife. But there are, as might well be expected, cases in 

 which even the mirror is of no avail, but in which we may still 

 suppose that stratification exists. A variety of experiments have 

 led me to think that the separation of the discharge into two 

 parts, viz. , the column of light extending from the positive ter- 

 minal, and the glow around the negative, with a dark space in- 

 tervening, may be a test of stratified discharge ; but I cannot 

 affirm anything certainly on this point. 



Chemical Society, May 18 — Prof. Abel, F.R.S., president, 

 in the chair. — The first paper read was on the action of malt 

 extract on starch, by Mr. C. O'Sullivan, showing that under 

 these circumstances it is converted into a mixture of maltose and 

 dextrin, the proportion of which varies with the temperature at 

 which the reaction takes place. — A communication was then 

 made by Dr. H. E , Armstrong and Mr. Gaskell on metaxenol, 

 the metadimethylated phenol. — There were also papers on the 

 gases enclosed in cannel coals and in jet, by Mr. J. W. 

 Thoma=, on phenomena accompanying the electrolysis of 

 water with oxidisable electrodes, by Dr. J. H. Gladstone and 

 Mr. A. Tribe, and on the estimation of hydrogen occluded by 

 copper, with special reference to organic analysis, by Dr. J. L. 

 W. Thudichum and Dr. H. W. Hake. 



Meteorological Society, May 17, — Mr. H. S. Eaton, 

 president, in the chair. — ^James Lloyd Ashbury, John Broun, 

 John Brown, Edmund Cruise, James Eldridge, George Gamett, 

 John Hopkinson, Robert Pick well, William Ford Stanley, 

 Rupert Swindells, Charles Tarrant, Thomas Taylor Smith, were 

 elected fellows of the Society. The following papers were 

 read : — Remarks on the present condition of maritime meteoro- 

 logy, by Robert li. Scott, F.R. S. This paper gives a history 

 of all that has been done in maritime meteorology since the 

 Brussels conference in 1853, up to the present time. — In the 

 mean temperature of every day at the Royal Observatory, Green- 

 wich, from 1814 to 1873, by James Glaisher, F.R.S. This 

 paper, which is a continuation of former ones on the same 

 subject, contains the observations for the ten years, 1864 to 1873, 

 which being combined with the previous ones, give the mean for 

 sixty years. On the meteorology of Mozufferpore, Tinhoot, for 

 1875, by C. H, Pearson. — New wind chart, by Lieut. -Col. G. E. 

 Bulger. 



Physical Society, May 13. — Prof. G. C. Foster, president, 

 in the chair. — The following candidates were elected members 

 of the Society : — Prof. T. Andrews, Rev. R. H. M, Bosanquet, 

 M.A., and David Howard. — Mr. Thompson, B.A., B.Sc, con- 

 cluded the communication on the supposed new force, which he 

 commenced at the last meeting of the Society. In the arrange- 

 ment which he has adopted for obtaining the spark, the secon- 

 dary current of a Rhumkorff's coil is made to traverse a short 

 coil of wire which is thoroughly insulated from the internal core, 

 and into the circuit an arrangement is introduced by means of 

 which the current may be made to traverse a variable thickness of 

 air in its course round the short coil. It is found that if this 

 spark is very short the spark obtained from the internal core is 

 also short, but as we increase the thickness of air to be tra- 

 versed, the spark which may be drawn off increases ; the great- 

 est effect, however, is produced when one terminal of the coil is 

 connected with the earth, the spark then obtained being about 

 half an inch in diameter. Mr. Edison considered that the spark 

 was retro-active, but Mr. Thompson showed, by an experiment, 



