, Mr Edmondston on the Coly'ntbiis Grylle^ 105 
Colymhus Minov or Lesser Guillemot.— Pica or Black- 
billed Auk. 
These I concur with that indefatigable and intelhgent orni- 
thologist Dr Latham, in considering as the immature birds of the 
foolish guillemot and razor-bill. My reasons for this opinion 
I shall reserve till the observations I propose making on these 
species during this summer in Zetland be completed. 
Montagu’s reasoning on the other side, is very full and inge- 
nious, though certainly founded on too partial observation^ 
Edinburgh, \ 
^Ist April m2, i 
Art. XVII. — On a species of Earthy Matter spontaneously 
Combustible. By John Murray, Esq. F. L. S., M. W. S., 
&c. &c. Communicated by the Author. 
As you had the goodnes to insert in a former number of the 
Edinburgh Philosophical Journal, the results of a chemical in- 
vestigation of the properties of a liquid matter which I collect- 
ed in the crater of Vesuvius, I have taken the liberty of sub- 
mitting a description of a peculiar species of earthy matter, dug 
up ""at Ashleyhag^ in the parish of Wirlisworlc^ Derbyshire^ 
which is remarkable for its spontaneous combustion. I have 
not been able to submit it to a very minute examination, but 
intend to do this when at leisure, and I may then have it in my 
power to send you a more rigorous analysis. This remarkable 
earthy matter was discovered about fifteen years ago, about six 
feet below the surface soil, by labourers engaged in soughing” 
some land, situated on a declivity nearly at the bage and SW. 
side of Allpont, the greatest elevation in the south of Derby- 
shire. The following are the strata incumbent on thi^ sub- 
stance : 
Surface soil, from 6 to 8 inches deep. 
White clay, 2 feet thick. 
Blue clay, 3 feet thick. 
Then proceeds. 
The substance referred to, S feet thick. 
