342 
Dr Fyfe’s Hydro-Pneumatic Lamp . 
ceasing when the acid gets below the zinc, there is thus always 
a supply of gas subjected to the pressure of a column of fluid of 
from six to seven inches. When the stop-cock, therefore, is 
opened, the hydrogen is propelled against the platinum ; the 
fluid falls into the short limb ; and as the zinc is thus again sur- 
rounded by acid, more gas is generated to serve for the next 
time. The distance of the platinum depends on the size of the 
bore of the stop-cock ; but as the ring E is moveable, it can be 
easily adjusted. 
The apparatus described contains only about a cubic inch of 
gas; but I find it is sufficient for affording a light, for, though 
it does not ignite the platinum long enough to kindle the gas, 
yet there is sufficient heat to set fire to a sulphuric match. The 
moment, then, that the platinum becomes red-hot, a small sul- 
phuric match must be applied to it. The only circumstance to 
be attended to, is to allow the match to remain ignited for a few 
seconds, with a view of driving off any sulphur that may be left 
adhering, and which prevents the ignition when the gas is again 
impelled on it. I would therefore recommend, that, each 
time it is used, the flame of the match be kept at it for a short 
time. 
I am aware that many improvements on this lamp might be 
suggested, and which, it must be admitted, would make it more 
complete, but they detract from one of its greatest qualifications, 
cheapness ; the lamp, as described, being purchased for about 
ten shillings. 
Art. 'XVIII. — Account of several new Species erf Combretum , 
Chailletea , Clerodendrum , Gomphia, Modecia, Musseenda, Jus- 
ticia , B rillantaisi a , P armarium and Anthocliesta^ from Sierra 
Leone . By Mr George Don, A. L. S. 
In a voyage undertaken by me in 1822 and 1823, for the pur- 
pose of collecting seeds and plants for the Horticultural Society 
of London, I visited the western coast of Africa, the Brazils, 
some of the West India islands, and New York. Perhaps the 
most interesting spot I visited, was the colony of Sierra Leone, 
where I remained from the 18th of February 1822 till the 11th 
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