Volume 21, Issue 6
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Features
Objects of Interest on a Guano Island
Effect of Magnetism on Time-Pieces
On Ropemaking
The Diamond Bone Mill
The Shad Fisheries of the Hudson
Adverse Report on the East River Bridge
A New Lamp Extinguisher
Small Inventions Most Profitable
Obituary—Death of John A. Roebling
Balancing Heavy Cylinders
Currency Reform Needed—How it May be Accomplished
Joshua Shaw, Artist and Inventor—The Early History of the Copper Percussion Cap
Manufacturing, Mining, and Railroad Items
Calculation of the Amount of Ice Which Can be Produced From a Given Amount of Coal in the Modern Ice Machine
Answers to Correspondents
Recent American and Foreign Patents
Official List of Patents
Issued by the United States Patent Office