General view of an apparatus used for the spectroscopic study of the mechanism of nitrogen fixation in the electric arc at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington,…

Two views of assorted apparatus at the Fixed Nitrogen Research Laboratory's Urea Plant. Urea is a water-soluble powder form of carbonic acid frequently used as a fertilizer and feed supplement. The individuals present…

For mortar-fired fireballs.

Fig. 103: Illustration of how instrument in figure 100 is used.

Fig. 100: Instrument to find the center of a mortar's mouth.
Fig. 101: Stone scale.
Fig. 102: Metal ring to measure caliber.

Fig. 96: Wooden shim to adjust the grade.
Fig. 97: Compass.
Fig. 98: Calipers.

Figure 116 is described in the text as a wad hook. The pictured instrument appears to be an inclinometer.

Fig. 114: Diagram of method to test the quality of the cast form of artillery.
Fig. 115: Tool to test whether the bore is pitted.

Figs. 108-109 and 112: Steel needles to clean the touch hole.
Fig. 110: Nuremberg scale for iron, lead, and stone.
Fig. 111: Square.

Fig. 104: Double hackbut or large wall gun.
Fig. 105: Diagram of a loading shovel for artillery.
Fig. 106: Diagram to calculate the caliber of stone ball relative to the mouth of the barrel.

Fig. 94: Cross-section of a mortar.
Fig. 95: Mortar carriage.

Fig. 90: Cross-section of a petard.
Fig. 91: Reinforced madrier (above) and cut-away perspectival view of how the petard mounts into the madrier (below).

Fig. 85: Storm keg.
Fig. 86: Storm pot.
Fig. 87: Storm keg.

Fig. 81: Cartridge for pyrotechnic hail described in text as figure 80.
Fig. 82: Storm wreath.

Fig. 65: Mortar-fired rock grenade.
Fig. 66: Diagram for glass grenade.
Fig. 67: Diagram for iron grenade.
Fig. 68: Diagram for lead grenade.
Fig. 69: General diagram for grenade holes.

Figs. 70-71: Combustion tubes in grenades.
Figs. 72-74: Grenades.