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F. IF. ELLIS.
(PL XI. Fîg. I). The tube B is held vertically by the clamp 0. A is
the paraffin piston, D is a perforated stopper through which passes the
glass tube E. The tube E should project above the level of the stopper
in order to prevent any oil that may collect at the bottom of the tube B
from running into the tube E. G is the slender piston rod of glass
terminating above in the paper stirrup H presently to be described.
M is a band of thin brass encircling the glass tube. The ends of the
band are bent at right angles to the tangent of the circle formed by it.
A piece of lead wire L is soldered to M ; this can be bent in any
direction. A screw N is fastened to the other extremity of the lead
wire. 0 is a piece of wrood or brass shown in a front view at Fig. 3.
P is a small disc of cork with a pin axis. The sharpened extremities
of the axis are received into corresponding depressions in the two lateral
screws. The needles I and Q are thrust into this cork. The needle Q
has a thread cut upon it ; and the small counterpoise JR may be screwed
backwards and forwards. The needle I may be attached to the paper
marker K directly or by means of an intermediate piece of straw,
broom-corn, or other light substance. In constructing very delicate
recorders I have made the entire lever of paper with the exception of
the small piece of needle necessary to attach it to the cork disc.
A long paper marker slightly bent works with very little friction against
the smoked paper upon the recording cylinder, and is greatly superior
to tinsel for delicate work. The connecting joint between the piston rod
and the recording lever must, necessarily, be a very delicate one : the
motion of the lever must not be impeded by it ; at the same time, the
joint must not be at all loose. A very satisfactory joint may be
constructed as follows : A small piece of paper (H, seen in the front
at Fig. 2) has a small hole punched in its centre. A piece of thin
rubber or calves’ peritoneum is pasted over the hole with mucilage.
The paper stirrup is fastened to the piston-rod by means of sealing-wax.
The needle I is thrust through the membrane covering the hole in the
paper.
The pistons are very easily constructed. Small pistons may be cut
out of the paraffin with a sharp cork-borer. Larger pistons can be
readily made with a foot lathe. A small hole is made in the centre of
the piston, and into this is cemented the piston-rod by means of a
hot wire. The rubber tube F connects the recorder with the other
apparatus with which it is used. Between this apparatus and the
recorder there must be a lateral opening to be opened or closed as
required. In adjusting the apparatus it is necessary that this should