146 REPORT — 1866. 



portion) of the time that they continue visible. Their condition is then 

 exactly that of a flame of gas in a Bunsen's burner, freely charged with the 

 vapour of burning sodium, or of the flame of a spirit-lamp newly trimmed 

 and largely dosed with a supply of moistened salt. 



<' Itis difficult to believe that the vapour of the metal sodium exists in such 

 considerable quantities at the confines of the atmosphere. It is much more 

 reasonable to suppose that it is brought into the atmosphere by the meteors 

 themselves, so as to be deposited in the luminous trains that mark their 

 course. The material of the August meteors is, therefore, probably a mineral 

 substance in which sodium is one of the chemical ingredients. Such is the 

 rather satisfactory termination of an experiment which it will be very easy 

 to repeat whenever an abundance of meteors on the night of the 10th of 

 August offers an equally favourable opportunity for examiaing their spectra 

 by the aid of the meteor spectroscope. 



"The connexion believed by adherents of Chladni to exist between shooting- 

 stars and aerolites is now shown, at least in August, to extend itself in some 

 measure to their chemical composition. The meteorites of Aumale, which fell 

 on the 25th of August 1865, were found, on analysis by M. Daubree, to con- 

 tain soluble salts (chloride and carbonate) of sochum. A circumstance so un- 

 common in the composition of aeroUtes, allies the meteorites of Aumale very 

 closely with the sodium -bearing streaks of the meteors of the 10th of August. 



" In this manner, each new acquisition of knowledge, however unforeseen 

 may be its origin, tends to support the theory of Chladni, and to confirm the 

 belief that shower-meteors and shooting-stars are actually aerolites of small 

 dimensions. In whatever manner aerolites and shooting-stars are related to 

 each other in their astronomical and other peculiarities, they wlH evidently 

 require a vast number of further experiments to unfold their real source." 



Report of the Committee appointed to Investigate the Alum Bay Leaf- 

 Bed. By W. Stephen Mitchell^ LL.B., F.G.S., Caius College, 

 Cambridge. 



Thk bed known to geologists as the " Leaf-bed," or " Pipe-clay bed," of 

 Alum Bay, is the band of white clay which occurs in the lower Bagshot beds 

 in Alum Bay, about 200 feet from their base (No. 42 in Memoir of the 

 Geological Survey). It is about 6 feet thick ; but one portion only, a few 

 inches in thickness, contains the plant-remains. No other oi-ganic remains 

 whatever have been noticed. 



The occurrence of these plant-remains was first observed by Mr. Prestwich 

 (see Geol. Soc. Journ. 1847, p. 395), and since then collections have been made. 



Dr. P. de la Harpe, of Lausanne, examined these, and gave a notice of 

 several species in a paper on the " Flore tertiaire de I'Angleterre," which 

 appeared in the ' Bulletin de la Societe Yaudoise des Sciences NatureUes ' 

 for June 1856. In December 1860, in conjunction with Mr. J. "W. Salter, 

 F.G.S., he prepared the list which is published in the memoir of the Geological 

 Survey of the Isle of Wight. 



This list includes the collections from '■ the same strata worked at Bourne- 

 mouth and Corfe Castle, in Purbeck, Dorset ; " yet for the compilation of it 



