659 



MISCELLANEA. 



Notes on Diatomaceous Earth from Lord Howe Island. 



Mr. Walter Howchin on April 12, 1917, exhibited a 

 large piece of diatomaceous earth from Lord Howe Island, 

 and offered the following remarks on it : — The stone was 

 obtained by Mr. A. M. Lea from Mr. J. B. Water house 

 during the former's recent visit to the island. Mr. Waterhouse 

 stated that in the year 1911 a considerable quantity of this 

 stone was washed up on the beach, and attracted much atten- 

 tion on account of its peculiar appearance and lightness. Mr. 

 Howchin stated that he had carefully examined the rock with 

 the following results : — The grain of the stone is excessively 

 fine and remarkably uniform, and, with the exception of a 

 few brown specs, which on closer examination proved to be 

 small fish scales, no defined objects could be distinguished by 

 the unaided eye. A microscopical examination showed that 

 the stone consisted of very finely-divided flocculent .matter in 

 which was embedded great numbers of diatoms, chiefly 

 belonging to the discoid genus, C oscinodiscus , of which several 

 species are present, in addition to which are numerous sponge 

 spicules (chiefly monactinellid), a few radiolaria, and the fish 

 scales already mentioned. The organic contents prove it to be 

 a marine deposit, but of somewhat uncertain origin. The 

 extreme fineness of the particles, the absence of land wash, as 

 well as the absence of foraminifera and other small organisms, 

 that are almost always more or less present in marine deposits, 

 indicate that it must have been laid down under unusual con- 

 ditions. Mr. W. S. Chapman, Assay er at the School of 

 Mines, has been kind enough to supply the following partial 

 analysis of the stone : — 



Per cent. 



Moisture 



37 



Combined water (and organic) 



.. 57 



Silica 



.. 63-8 



Alumina 



.. 59 



Iron oxide 



.. 3-0 



Lime 



.. 2'2 



Magnesia 



.. 7-9 



(Alkalies not determined) 





922 



The amount of silica present is not equal to that of a rela- 

 tively pure diatomaceous earth, and the presence of magnesia, 



