187G.J Mr. W. Spottiswoode on Stratified Discharges, 73 



simple organization, approximating somewhat closely to that of the ovules 

 of Jiuiiperus, Callitris, and Wehvitschia. 



Some small seeds, which appear to be identical with the Cardiocarpum 

 teneUum of Dawson, found in great numbers on slabs of shale by Mr. 

 John Smith, of Kilwinning, in Ayrshire, are described. They were found 

 in the upper Coal-measures near Stonehouse in Lanarkshire. 



The last form noticed is a very curious winged seed from the upper- 

 most Coal-measures of Ardwick, at Manchester, and which appears to 

 have been a double seed, resembling in general form the samara of an 

 ash. It belongs to Brongniart's genus Polypterospermum. 



The fact that large numbers of seeds of uumistakable flowering plants 

 exhibit very close resemblance to the ovules of G-ymnospermous seeds 

 is a very important one. Prof. Newberry has obtained such seeds in 

 America ; M. Grand-Eury has done the same thing in France ; and it now 

 appears that, though attention has but very recently been drawn to the 

 existence of the smaller forms now described in the British Coal-measures, 

 the discovery of a considerable variety has already rewarded the researches 

 of the author and his auxiliary friends. There is no doubt that further 

 research will materially increase that number. The question naturally 

 arises, where are the Gymnospermous plants to which these seeds 

 belonged ? Finding the latter in the thin " upper-foot" coal-seam suggests 

 that other remains of their parent stems should also be found there. 

 The Dadoxylons are the only ones which exhibit any probability of such 

 relationship. But these have chiefly been found in the marine Ganister 

 bed, which underlies the upper-foot coal from which the majority of the 

 seeds have been derived, indicating that the Dadoxylons grew apart from 

 the Calamites and Lycopods abounding in the coal side by side with the 

 seeds. Time alone can solve these problems, as well as others relating 

 to the true homologies of some of the structures contained within these 

 seeds. 



V. On Stratified Discharges. — II. Observations with a Revolv- 

 ing Mirror By William Spottiswoode, M.A., Treas. R.S. 



Received May 3, 1876. 



In a paper published in Poggendorffs 'Annalen,' Jubelband, p. 32, 

 A. Wiillner has described a series of observations made, by means of a 

 revolving mirror, upon the discharge of a large induction-coil through 

 tubes containing ordinary atmospheric air at various degrees of pressure. 

 When, as is generally the case with an induction-spark, the discharge 

 occupies an appreciable interval of time, the image in the mirror appears 

 spread out to a breadth proportional to the duration and to the velocity 

 of rotation. The successive phases of the phenomena then appear, as 

 usual, arranged in successive positions, and may be studied separately, 

 even when too rapid to be disentangled by the unassisted eye. 



