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The Rowell-Potter System of Railway Signaling

By Frank C. Perkins

Edison's Inventions.— I

Their Commercial Value to the World

By Frank. L. Dyer and T. Commerford Martin

Extraction of Potash and Soda from Minerals

Influence of Over-Voltage on the Life of Metallic-Filament Lamps

Testing the Hardness of Metals

A Review of Methods in use

Safeguarding Wood against Ants

The Efficiency of Aerial Propellers

A New Investigation and its Results

By W.R. Turnbull

Experimenting with Animals and Plants

Studies in Artificial Mutation

By R. France

The Sense of Hearing in Insects

By K. Sajo

Silver Plating

The Various Methods now in use

Saponification with Ammonia

Science Interpreted by Children

Scale for Barometers

By C. D. Cheney

Wave Motion Visually Presented

Projection Demonstration to Accompany Lectures on Wave Motion

By Will C. Baker

A Writing Cam

A Novel Piece of Mechanism

By A. E. Schulz

Recent Progress in the Manufacture of Various Gases

A Noteworthy Anthropological Discovery

Stuttering and Stammering

The Psychology of Speech

Weeds that are used in Medicine

Some Simple Botanical Facts

By Emmett C. Hall

Electrical Notes

Engineering Notes

Trade Notes and Formulæ


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    April 03, 1909