An electrical drop recorder / by P.P. Laidlaw.

  • Laidlaw, Patrick P. (Patrick Playfair), Sir, 1881-1940.
Date:
1910?]
Catalogue details

Licence: Public Domain Mark

Credit: An electrical drop recorder / by P.P. Laidlaw. Source: Wellcome Collection.

    5/6 (page 2)
    9 which in turn is fixed to a short length of glass tubing through which a needle is passed, forming the axis of the lever. A short glass spring C (which is made by drawing out a piece of glass rod) presses upon the cork plate just beyond the axis of the lever, and maintains the lever in the horizontal position. A short piece of metal is fixed at right angles to the lever at L. From either end of this cross piece two wires P, P1 descend vertically to two mercury cups K, K1. One of these wires has a flattened end and is sufficiently long to be permanently immersed in the mer¬ cury of its cup. The other has a sharp platinum point which is just above the surface of the mercury. This mercury cup Kl has a levelling screw S. The mercury cups are embedded in a block which is fixed to a bar G. The axle of the on lever is fixed in another support F which is in turn supported by bar G. Bar G and glass spring C are attached to a stand by means of boss heads. A drop hitting the celluloid plate causes a downward movement of the lever and a connexion between the mercury cups. These are put in circuit with an electric signal and a suitable battery. Adjustment of the mercury level just below the platinum contact point ensures a single contact for each drop. The delicacy of the instrument is increased by using a fine glass spring and decreased by using a stouter one.