Note 9 — LECTURE I. ELECTRICAL INSTRUMENTS.
Reading edition
A little care is needed to regulate the vibrating needle. The spring should but barely touch the hammer, the adjustment being almost entirely regulated by the protrusion or retraction of the needle by the action of its screw; and the slightest twist of this screw will be sufficient. When the vibration is uneven or stops, and careful manipulation of the needle fails to re-establish it, remove the needle and clean its point as directed in the text.