296 PROCEEDINGS OF SECTION B. 



2. The melting point of P. undulatiun gum-resin is 



lower than that of P. Z>zco/or, doubtless because of 

 the higher percentage of resin it contains. 



3. The gum-resin of P. hicolor has the greater tendency 



to indurate, doubtless owing to the higher percentage 

 of gum it contains. In P. hicolor the outer portion 

 of the lumps consists of the dried gum-resin minus 

 the volatile oil with which it was associated, and the 

 intractability of this indurated substance with sol- 

 vents appears to ai'ise partly from the intimate 

 association of the gum and resin, and partly because 

 of Aveathering. 

 A. The resin of P. hicolor is of an orange-yellow colour, 

 differing from that of P. undulatum, which is almost 

 colourless in samples I have examined. 



Pittosporum rhomhifolium. " White Holly " of the 

 Richmond River. 



A small quantity of gum-resin has been collected from this 

 species ; it does not appear to be sensibly different to that 

 of P. undulatum. 



I desire to express my obligations to my Laboratory 

 Assistant, Mr. Henry G. fSniitii, for much valuable help in 

 the preparation of this paper. 



14.— ON THE PRESENCE OF MAGNETITE IN 

 CERTAIN MINERALS AND ROCKS. 



By A. LIVERSIDGE, U.K., F.R.S., Professor of Chcinistnj in the 

 University of Sydney. 



The following experiments to determine the amount of 

 magnetite or of magnetic particles in minerals and certain 

 rocks were made in consequence of the following statement in 

 Bauerman's Systematic Mineralogy, p. 298, 1881 ; viz. — 

 " Chrome iron and Franklinite are magnetic, but it is not 

 certainly known w^hether this is a special property or caused 

 by finely interspersed magnetite." ()ther writers, like Dana, 

 simply state that the above minerals are magnetic, but do not 

 make any comment as to whether the magnetic properties are 

 inherent in the minerals named or due to enclosed magnetite ; 



