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same diameter, and an inch high ; but I soon found that 
the warmth communicated to the air by the hand when 
holding the lamp by its handle, frequently encreased the 
elasticity of the air to such a degree, as frequently to pro¬ 
pel part of it through the hole, and in passing out, it almost 
invariably pushed before it a certain quantity of oil which 
proceeding through the vertical pipe in the stopper spread 
itself over the handle. To remedy this defect, which alone 
is sufficient to render the lamp useless, I have employed a 
method which has been completely successful. 
Having removed the small vertical pipe on the stopper, 
I substituted in its place, a small case of tin, eight lines 
broad below, and one inch high, soldered at its base to the 
upper surface of the stopper, and having at its top a small 
hole, about half a line in diameter. The oil being propell¬ 
ed by the air, through the centre of the stopper into the 
cavity of the cone, is enabled to diffuse itself and permits 
the air to escape at the same time, and afterwards returns 
drop by drop into the reservoir. 
To guard still more cautiously against any accident of 
this kind, I have placed on the top of the small conical ca¬ 
vity, a vertical pipe two lines in diameter and four or five 
lines in length. This hinders the oil driven by accident into 
the conical chamber, from proceeding during its agitation 
to the upper aperture through which the air passes out; 
thus preventing the air in any case whatever when issuing 
out of the lamp, from propelling the oil before it. 
Experience informed me, that all these precautions were 
necessary to remedy so embarrassing a defect. Another 
imperfection common to all kinds of lamps, that of diffus¬ 
ing an unpleasant odour whenever they burn with a small 
flame, has given me no less trouble, but I believe I have 
discovered a very simple remedy. To judge correctly on 
its efficacy, it is necessary to examine the cause and nature 
of the evil it is intended to remove. 
We all know that a lamp, with a double current of air, 
