Amateur Astronomy
Valuable Contributions made by Volunteer Workers in the Field
Volume 75, Issue 1939supp
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Features
Halos in Minerals
Markings Due to Radium in Rocks, and their Significance
Cost of Ice making in Small Plants
Lighthouses and Buoys of New York Harbor
Safeguards for the Mariner
Progress in Power Production
A Forecast of the Direction of Future Developments
Prime Movers
Our Debt to James Watt
Unmounting and Remounting Photographs
Notes on New York City's Water Supply System
Some Features of Interest at and about Kensico Reservoir
Modern Pumps of High Vacua
The Lowest Pressure ever Attained
A Strange Case of Abnormal Anatomy
Ten Years of Government Irrigation Work
A Review of the Activities and Experiences of the United States Reclamation Service since the Passage of the Newlands Act