of Edinburgh, Session 1880-81. 
117 
The following Communications were read 
1. On a Simple and Accurate Method of determining the 
Longitude of a Place by a Single Observer, without the 
aid of any instrument for measuring time. By Professor 
G-. Forbes. 
2. Stilbite, from Kerguelen’s Island. By A. Liversidge, 
Assoc. Eoyal School of Mines, Professor of Geology and 
Mineralogy, University of Sydney. Communicated by 
Mr J. Y. Buchanan. 
I am indebted to the kindness of my friend Mr J. Y. Buchanan, 
M.A., the chemist and physicist to the “Challenger” expedition 
for the specimen which forms the subject of this note. 
In speaking of the geology of Kerguelen Island, Mr Buchanan 
thus describes the occurrence of this zeolite ( vide Proc. Eoy. Soc., 
vol. xxiv. p. 617). 
“ The horizontal beds which form the mass of the land are basaltic, 
and vary from 10 to 20 feet in thickness, being generally compact; 
but, in ascending the hill, beds are met with frequently, which 
contain large amygdaloidal cavities filled with zeolites, principally 
analcite and heulandite (stilbite). These minerals are very plentiful 
in this part of the island, and when rounded by the action of the 
water they form remarkable white pebbles on the otherwise dark- 
coloured volcanic sand. Up to the summit the alternation of beds 
of compact sub-columnar rock of amygdaloid is pretty regular. 
“ The amygdaloid is of two kinds : in the one the cells are small, 
very thickly disseminated, and completely filled up by a zeolitic 
mineral ; the other has larger cavities, less thickly spread, and 
generally only coated with crystals, while seams filled with crystal- 
line matter are also frequently met with. The cavities contain 
generally analcite ; the seams, heulandite ” (stilbite). 
In quoting the above extract, I have ventured to insert the name 
stilbite after heulandite, since both names have been applied to the 
same mineral. Personally, I should call the specimen stilbite, inas- 
much as it agrees with the mineral known as stilbite by English 
