60 Mr. W. Spottiswoode on Stratified Discharges. [Jan. 31, 



form a stage in the growth, of the gland. In the matnre state of the 

 organ in this animal I consider that the vesicles, as usually supposed, 

 consist of cavities more or less spherical in shape, which are not in 

 communication with one another. 



The points mentioned in this note, together with others connected 

 with the subject, will be fully discussed in a future paper. 



II. " On Stratified Discharges. V. Discharge from a Con- 

 denser of Large Capacity." By William Spottiswoode, 

 M.A., LL.D., Treas. and V.P.R.S. Received November 22, 

 1877. 



The principal object of the following communication is to describe 

 an instrumental arrangement which has proved very convenient for the 

 production of steady strias. The first attempt which was made nearly 

 two years ago (February, 1876), consisted in charging a Leyden bat- 

 tery of nine large jars by means of an induction coil, and discharging it 

 gradually through a vacuum tube. This was effected by connecting 

 one terminal of the tube with the outside of the battery, and present- 

 ing the other terminal, made pointed, to a knob connected with the 

 inside, at suitable distances. The following effects were then observed : 

 (1.) When the interval between the terminal and the knob was 

 considerably greater than striking distance, the appearance in the tube 

 was cloudy and apparently unstratified, or showed only faint indica- 

 tions of stratification. It was, in fact, very similar to that produced 

 by attaching one terminal of the tube to one of an induction coil, and 

 carrying the other to the earth. 



(2.) When the interval was within striking distance, the usual jar- 

 discharge without stratification or dark space took place. 



(3.) When the interval was slightly greater than striking distance, 

 but not so great as in the first case, a bright stratified discharge was 

 observed. The proper motion due to a decline in tension was shown by 

 a revolving mirror, and by a careful but rapid alteration in the distance 

 during discharge, the motion could be arrested or even reversed. The 

 duration of the whole, although long compared with a single flash from 

 an ordinary coil, did not exceed half a second. 



This experiment gave reason to hope that if a condenser of sufficient 

 capacity were constructed, the discharge might be prolonged, and even 

 varied, so as to allow an actual study of its various phases to be made. 



The next attempt was made during last summer with some con- 

 densing plates, constructed for cable purposes, and kindly lent to me 

 by Messrs. Latimer Clark, Muirhead, and Co. The results were in 

 every way calculated to encourage further steps. 



At the suggestion of Mr. De la Rue, and with the assistance of his 



