[Illustration: Diagram of apparatus as described in text]
To contrive a self-trimming lamp. Let A B C (fig. 33), be a lamp
through the mouth of which is inserted an iron bar, D E, capable of
sliding freely about the point E, and let the wick be wound loosely
about the bar. Place near a toothed wheel F, moving freely about an
axis, its teeth in contact with the iron bar, that, as the wheel
revolves, the wick may be pushed on by means of the teeth. Let the
opening for the oil be of considerable width, and when the oil is
poured in let a small basin float upon it, G, to which is attached a
perpendicular toothed bar, H, the teeth of which fit into the teeth of
the wheel. It will be found that, as the oil is consumed, the basin
sinks and causes the wheel F to revolve by means of the teeth of the
bar, and thus the wick is pushed on.
34. _A Vessel from which Liquid may be made to flow, on any portion of
Water being poured into it._
[Illustration: Diagram of apparatus as described in text]
If into a vessel, provided at the bottom with an open spout, liquid is
poured, the spout shall sometimes run from the first, sometimes when
the vessel is half filled, and sometimes not until the whole is filled:
in fine, when any proposed quantity of liquid has been poured in, the
spout shall run until all is exhausted. Let A B (fig. 34), be the
vessel, the neck of which is closed: insert the tube C D, air-tight,
through the partition, and let it reach to the bottom of the vessel
leaving only a passage for the water. Let E F G be a bent siphon,
the inner leg of which extends nearly to the bottom of the vessel,
while the other projects without, being fashioned in the shape of a
water-spout: the curve of the siphon must be close to the neck of the
vessel. In A B make an air-hole, H, near the partition and leading into
the body of the vessel. If we intend the spout to run immediately on
the entrance of the liquid, we must place the finger on the vent H, and
the spout will run, for as the air in the vessel has no way of retreat,
the liquid will rush out through the bent siphon. If we do not close H,
the liquid will pass into the body of the vessel, and the spout cannot
run until we again close the vent: and then, if we set the vent free,
the siphon will exhaust all the liquid.
35. _A Vessel which will hold a certain quantity of Liquid when the
supply is continuous, will only receive a portion of such Liquid if the
supply is intermittent._
A vessel can be made which, as long as you pour in any liquid, admits
it, but, if you once cease pouring, holds no more: the construction is
in this manner. Let A B (fig. 35), be a vessel, the neck of which is
closed by the partition C D. Through the partition insert the tube E F,
reaching nearly to the bottom, and projecting above the partition so as
almost to reach the brim of the vessel; and let this tube be encircled
by another G H, the top of which is closed by a lid, at a sufficient
interval from the partition and the tube E F to admit of the passage
of water: in A B make an air-hole, K, leading into the body of the
vessel. Now, if we pour liquid into the vessel’s neck, it will be found
that it will pass into the body through the tubes G H and E F, the
air retreating through the vent K. But, if we cease pouring, and the
neck of the vessel becomes empty, the air will break the continuity,
so that any liquid in G H will flow down and fall upon the partition;
for the breadth about the tube G H should be considerable, that the
water may fall by its own weight. If more liquid be poured in, the air
confined in the tubes E F and G H will not allow it to pass through, so
that it will run over the brim of the vessel.
36. _A Satyr pouring Water from a Wine-skin into a full Washing-Basin,
without making the contents overflow._
[Illustration: Diagram of apparatus as described in text]
Construct on a pedestal the figure of a satyr holding in his hands a
wine-skin: place near a washing-basin, and into this let some liquid
be poured until it is full; water shall be made to flow into the basin
without running over, until all the water in the skin is exhausted.
The following is the construction. Let A B (fig. 36), be a perfectly
air-tight pedestal, either cylindrical or octagonal in shape, as may
seem more elegant, and divided into two chambers by the partition C D,
through which the tube E F, fitting closely into the partition, extends
upwards nearly to the roof of the pedestal. Through the roof insert
the tube G H, projecting slightly above the vessel, and lying exactly
under the basin, while, below, it reaches to the bottom except that
room must be left for the passage of water: this tube must be soldered
into the roof of the pedestal and the partition. Another tube, K L M,
must also be inserted through the roof, reaching not quite so low as
the partition, soldered into the roof and carrying its stream into the
basin, which lies above the tube G H and communicates with it. Now let
the vessel A D be filled with water through an orifice N, which must
be afterwards closed. If water is poured into the basin, it will pass
through the tube G H into the vessel B C; and the air in B C, passing
through the tube E F and into the vessel A D, will force the liquid in
A D through K L M into the basin; and this being carried again into B
C will force out the contained air as before, which, again, will force
the water in the vessel A D into the basin: and this will go on until
the water in A D is exhausted. The tube K L M must pass through the
mouth of the skin and be particularly fine, that the display may last a
considerable time.