General Science. 
S19 
depends on the incipient reduction of the metallic oaide, as 
for instance, the transit of a peroxide into a> protoxide^ or a 
deutoxide into protoxide. I may cite an experiment which ap- 
pears to be conclusive. Into a curved tube, over mercury con- 
taining hydrogen desiccated with muriate of lime, pass a portion 
of deutoxide of barium^ and then apply the heat of a spirit- 
lamp ; a brilliant light .appears, the deutoxide becomes the prot- 
oxide, and protoxide of barium and water are the results. Just 
so it is with the magnesia, &c. in the oxy-hydrogen flame, and 
the earthy matter contained in the charcoal submitted to the 
action of galvanic agency. I should from hence summon a 
strong argument in favour of Dr Clarke’s asserted reduction of 
some of the earths. Thus manganese (to illustrate the position) 
is reduced from a peroxide to a protoxide with no very high tem- 
perature ; yet it demands exalted increments of heat to reduce 
it further into its reguline form, but we know it is done without 
electrical aid. I see no plausible reason why the earths may 
not be reduced by a supposable high temperature, without call- 
ing in galvanic agency, 
50. Spontaneous Combustions.- — The following account of a 
case of spontaneous combustion has been transmitted to us 
by Mr James Gullan of Glasgow. Having read an ar- 
ticle in your valuable work, November 5., on the spontaneous 
combustion of cloth, I send you an account of the following 
fact, which occurred in the year 1817. Having sold a respec- 
table spirit-dealer a parcel of sample-bottles, I sent them to him 
packed in an old basket, the bottom of which was much broken ; 
to prevent the bottles from falling through, I put across the 
bottom of the basket a piece of old packing-sheet, which had 
lain long about the warehouse, which was an oil and colour one, 
.and was besmeared with different kinds of vegetable oil. About 
six or eight weeks after, the gentleman informed me that my 
oily-eloth and basket had almost set his warehouse on fire. The 
basket and cloth had been thrown behind some spirit-casks 
pretty much confined from the air, and about mid-day he was 
alarmed by a smell of fire. Having moved away the casks in 
the direction where the smoke issued, he saw the basket and 
cloth in a blaze. This fact may be a useful hint to persons in 
