Drum
3 of the 7 encyclopedias on this shelf carry an entry for Drum. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a musical instrument formed by stretching parchment over the heads of a cylinder of wood or over a bowlshaped metallic vessel. The skin of the ass is a very superior article for the purpose. There are three kinds of drums: (1) The long drum or bass drum with two heads, held laterally and played on both ends with stuffed-knob drumsticks. (2) The side-drum, having two heads, the upper one only being played on by two sticks of wood; the lower head has occasionally strings of catgut stretched across its surface, and then it is called a snare drum. (3) The kettle-drum always employed in pairs. Of these (1) is the ordinary drum used by an infantry or marching band. It is employed mainly to mark the time, and also to increase the fortes. The big drum, or grosse caisse, of the modern orchestra, is a modification of the ordinary drum, with the diameter greatly increased, and the length of the cylinder lessened. It is struck on one side only. (2) Is the sidedrum of the fife and drum bands. It is occasionally employed in the orchestra for special effects. (3) Are either the small kettle-drums of the cavalry band, played on horseback; or the proper orchestral drums, larger in size, but similar in construction. The tambourine is a species of drum, consisting of a single skin on a frame or vessel open at bottom. The heads are tightened by cords and braces, or by rods and screws. The drum was a martial instrument among the ancient Egyptians, as the sculptures of Thebes testify. Their long drum was like the Indian tam-tam, and was beaten by the hand. The invention of the drum is ascribed to Bacchus, who, according to Polygenus, gave his signal of battle by cymbal and drum.
Aiton's Encyclopedia (1910)
a musical instrument played by percussion or pounding. The ordinary drum consists of a wooden or metal cylinder, shaped like a cheese hoop. A circular sheet of parchment, called a head, is stretched taut over each end, and held in place by a hoop. Cords interlacing from hoop to hoop serve to regulate the tightness of the drumheads. The tighter the vellum, the higher the note. The tambourine, the timbrel, and the drum are all of Eastern origin; the former two are played by the fingers. The drum is played with sticks. A snare drum is played by two sticks on the same end. It is a regular accompaniment of the fife. The large bass drum is sometimes called the Turkish drum. It is played by two padded sticks, one at each end. It is a regular feature of a military band, and has its place in the orchestra. The kettledrum used in the orchestra is a hemispherical metal basin covered with vellum and resting usually in a tripod. It may be tightened by screws. Kettledrums are played in pairs--one being tuned a fourth below the other. See Orchestra
American Watchmaker and Jeweler (1892)
The barrel of a turret clock on which the driving cord is wound. There is a variety of escapement, known as the Drum Escapement, which is met with but little in this country. Britten says this variety of escapement is a continual source of trouble to English repairers. It receives impulse from every other vibration only, and the idea of the escapement appears to be, that by providing a long frictional rest on one of the pallets, the extra pressure of the escape wheel tooth, when the mainspring is fully wound, will be sufficient to prevent any considerable increase in the arc of vibration of the pendulum. Clocks with this escapement, however, often stop from the diminished power when the spring is nearly run down, again, when it is fully wound, will be sufficient to prevent any considerable increase in the arc of vibration of the pendulum. Clocks with this escapement, however, often stop from the diminished power when the spring is nearly run down, again, when it is fully wound, because the small and light pendulum has not the energy to unlock the pallet.