102 On the Properties of Sulphur. Presents. [Dec. 6, 



The formation of a film of lower refractive index on the glass 

 would account for the defect in the reflected light ; but to account for 

 the excess, it seems necessary 'to assume that the polishing has 

 increased the optical density of the surface-layer, and the changes 

 produced in the amount of light transmitted and in the angle of 

 polarisation support this view. 



After being polished, the surface of flint glass seems to alter some- 

 what readily, the amount of the reflected light decreasing, and the 

 amount of the transmitted increasing, whilst with crown glass the 

 change, if any, proceeds very slowly. 



There is no evidence to show to what particular cause these 

 changes are due. 



The values of the transmission coefficients for light of mean 

 refrangibility for the two particular kinds of glass are given, and 

 show that for 1 cm. the loss by obstruction amounts to 2 '62 per cent, 

 wiih.the crown glass and 1*15 per cent, with the flint glass. 



IV. " The Specific Resistance and other Properties of Sulphur." 

 By JAMES MONCKMAN, D.Sc. Communicated by Professor 

 J.' J. THOMSON, F.R.S. Received November 10, 1888. 



'[Publication deferred.] 



Presents, December 6, 1888. 

 Transactions. 



Freiburg-im-Breisgau : Naturforschende Gesellschaft. Berichte. 



Bd. II. 8vo. Freiburg 1887. The Society. 



Gloucester: Cotteswold Naturalists' Field Club. Proceedings. 



1887-1888. 8vo. Gloucester-, The Origin of the Cotteswold 



Field Club. By W. C. Lucy. 8vo. Gloucester 1888. 



The Club. 



Haarlem: Musee Teyler. Archives. 8vo. Harlem 1888; Cata- 

 logue de la Bibliotheque. Livr. 7-8. 8vo. Harlem 1887-88. 



The Museum. 



Halle: Verein fur Erdkunde. Mittheilungen. 1881. 8vo. Halle. 



1881. The Verein. 



Hamburg: Naturhistorisches Museum. Bericht. 1887. 8vo. 



Hamburg 1888. The Museum. 



Helsingfors : Finska Vetenskaps-Societet. Acta. Tom. XV. 



4to. Helsingfors 1888 ; Bidrag till Kannedom af Finlands 



Natur och Folk. Haftet 45-47. 8vo. Helsingfors 1887-88 ; 



Ofversigt. XXVIII-XXIX. 8vo. Helsingfors 1886-87; Dess 



