Gongs are cheese-shaped metallic hollow suspended vessels, and are struck by a muffled hammer.

Musical sounds are also produced from slips of glass, or chilled iron, glass bells and tumblers, and also from resonant magnetic iron blocks.

[1924], [1925], [1926]. See [Sec. 98].

[Larger plate.]

Section 106.—DOORS, MANHOLES AND COVERS.

[1927]. Application of a single crosshead and bolt to close two covers, as in a pump clack-box.

[1928]. Cone seated cover, with hand-lifting crossbar and recess.

[1929]. Crosshead and man- or mud-hole, as commonly used for boilers, &c.