weighed 3 grammes. Rubidium closely resembles potassium 
in its properties, its vapour possesses a greenish blue colour, 
the specific gravity of the metal is 1’65, it is more electro- 
positive than potassium, and it melts at the very low tempera- 
ture of 38’5° C.” 
In reference to the age of the New South Wales coalfield, 
Mr. Edward Hull stated that he had received letters from 
the Rev. W. B. Clarke, who has for many years been engaged 
in its exploration, and from Mr. John Mackenzie, who has 
had considerable experience as a mining surveyor in Wigan 
and North Wales. It is well known that Mr. Clarke main- 
tains the Palaeozoic ago of the carbonaceous deposits of New 
South Wales, in opposition to Professor M c -Coy, who. holds 
that they are of more recent formation (Mesozoic). As 
Professor M c -Coy has never actually visited the New South 
Wales coalfield, and derives his information from cabinet 
specimens, men of science will probably prefer the evidence 
of one who has spent years in personally exploring and 
collecting from the beds themselves. In Mr. Clarke’s 
Memoir on the “ Recent Geological Discoveries in Austral- 
asia” (2nd edit.), the author defends his view of the Palaeozoic 
age of the coal-bearing strata ; and in the letter from Mr. 
Mackenzie, the writer gives the following series of fossiliferous 
strata overlying the coal and canncl belonging to the lion. 
B. Russell, which, if correct (as there is every reason for 
supposing), ought to set the question at rest in favour of the 
true Carboniferous age of the coal-measures. lie states — “ In 
a pit above this coal arc strata with Fenestella, Stcnojwra, Or- 
thonota costata, Spirifer , Producta , Terebratula, &e. In a pit 
about 100 feet below the same coal occur Spirifer, Producta, 
Conularia, and vegetable impressions ; about 60 feet lower, 
Spirifer, Terebratula, Plcarotomaria, Stenopcrci ; and similar 
shells, accompanied by vegetable remains, are stated to occur 
still lower. Mr. Mackenzie promises to send specimens of 
Lcpidodendron and Sigillaria from the same beds. 
