General view of a drillability apparatus with fertilizer hoppers, a starwheel, and rotating plate mechanism at an unidentified U.S. Department of Agriculture facility.

Three views of the Engine Room at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. showing assorted machinery and apparatus.

The Fixed Nitrogen Research Laboratory…

General view of a Stokes Tablet Press at the U.S. Department of Agriculture's Agricultural Engineering Laboratory facility. A tablet press is a mechanical device that compresses granulated material into tablets or…

Close-up view of the interior of an apparatus likely used for the manufacture and/or testing of fertilizer at an unidentified U.S. Department of Agriculture facility.

General view of granulation equipment used at the U.S. Department of Agriculture's Agricultural Engineering Laboratory located in Beltsville, Maryland. This equipment is believed to have been used by chemist John O.…

General view of small-scale continuous granulation equipment used at the U.S. Department of Agriculture's Agricultural Engineering Laboratory.

General view of an unidentified room at the U.S. Department of Agriculture's Agricultural Engineering Laboratory showing a drillability apparatus with fertilizer hoppers, a starwheel, and rotating plate mechanism.

General view of the drillability machine at the U.S. Department of Agriculture's Agricultural Engineering Laboratory showing the distribution of wet granular fertilizer as deposited by the Grether hopper.

General view of an International Fertilizer Distributor (No. 49 Machine) in use at the U.S. Department of Agriculture's Plant Industry Station facility in Beltsville, Maryland. This machine was used to determine the…

General view of an unidentified apparatus, possibly a pump or compressor, used at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen Research…

Close-up view of the mounting frame and driving mechanisms of the fertilizer distribution testing apparatus used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington…

General view of assorted equipment and apparatus in the Constant Humidity Room at the the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn…

General view of the indoor soil track used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. Measuring 9 feet wide by 70…

General view of the air-conditioning equipment used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. This particular…

General view of the fertilizer distribution testing apparatus used in the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. The…

General view of the machine shop at the U.S. Department of Agriculture's Fertilizer Machinery Laboratory located at the Arlington Experimental Farm in Rosslyn [Arlington], Virginia. Established by an act of Congress in…

Two views of the component parts of an apparatus used to grow higher plants in a sterile medium at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C.

The Fixed Nitrogen…

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.