284 New Outlines of Chemical Philosophy. 
In using the blow-pipe for experiment, a piece of charcoal is 
generally used to support the subject, and held in the flame of 
the lamp; the charcoal should be of a close compact grain, and 
properly burnt ; for, ifit is teo little carbonized, it will flame like 
a piece of wood, and obscure the object; and if it is too much 
burnt, it is so quickly consumed, and burnt to ashes, that the 
object is in danger of being lost im it; the charcoal greatly in- 
creases the heat, by reverberating the flame, and by heating the 
object at the opposite side; itself being converted into fuel, and 
excited by the blast, and thus creates an atmosphere of flame 
and heated air around it, which prevents the heat being carried 
off so fast, or the object being so much cooled, as if it should for 
an instant be moved out of the cone of the flame, from the un- 
steadiness of ite hand, or from accidental currents of air, which 
would disturb the fame, and cause such a wavering in the point | 
of the cone, as to divert it in some measure from the object. In 
order to prevent more tallow than is necessary from being con- 
sumed, to produce the intended effect, it is convenient to have 
several lamps with wicks of different thicknesses, viz. one to hold 
two flat cottous (such as are used for the Liverpool lamps) of 
about 1} inch broad; another to hold four, and a third to hold 
six, or as much common wick yarn as is equal to those wicks in 
bulk : glass jets should also be provided of different sized aper- 
tures, to suit the greater or lesser sized wicks and flames, and 
deliver streams of air upon them proportionately, and their jets 
should point upwards in a small degree: hogs-lard is also equal 
or perhaps superior to tallow for the lamp. 
LX. New Outlines of Chemical Philosophy. By Ez. WALKER, 
Esq. of Lynn, Norfotk. 
[Continued from p. 105.] 
Sirs, aly a paper published in the Philosophical Magazine, 
vol. xiii. p. 161, I described an electrometer, which I had con- 
trived for determining the mechanical forces of the two elements 
that compose the electric spark. From some experiments made 
with that instrument it appears that all electrical phenomena 
afe produced by two distinct powers acting in contrary directions, 
and with equal energy. At that time I had no other way of de- 
termining the equality of those forces, than by inspection ; but 
I have since added some improvements to the instrument, which 
make it more convenient and correct. 
The first improvement consists in cutting a hole through the 
; card, 
