JF Ptak Science Books

Cell vs. Cell: Photoelectric Cell and Shooting a Prisoner for Escaping their Cell (1930)

JF Ptak Science Books  Quick Post

The photoelectric cell was a mature invention (appearing in 1883) when it became armed and lethal in 1930.  Popular Mechanics published this photo (explained with only a caption and a paragraph) in its July 1930 issue. We see that should a prisoner make a dash up and over the prison wall, they interrupt the "electric eye" sentry which we read (1) fires a pistol positioned along the wall and (2) sounds an alarm, simultaneously.  It seems as though the alarm system could be reconstituted at the base of the wall, sounding an alarm before the prisoner got to the wall (let alone up and over it), rather than shooting as the alarm sounds.  The consequences of this idea--which I suspect was never implemented--were, well, rather extreme.

Non-Silhouette Silhouettes and Dirigible Mooring Masts (1930)

JF Ptak Science Books  Quick Post

Just a very quick entry here on some interesting and arresting images relating to flight, all from the July-December 1930 volume of Popular Mechanics. The first is a full-page illustration for October (1930) showing an improved method for anchoring dirigibles--in this case, for demonstration purposes, it is His Majesty's Airship airship R-100, which was over 700' long and moved along at about 80 mph, and was less than a year old. Unfortunately, this protocol for moving though the air was nearly exhausted--it was fateful for this note on the mooring masts appeared in October as this was the month of the R-101 disaster, which effectively brought the end of the R-100, which was scrapped soon afterwards.  

• "Sketch of Latest Type pf Mooring Mast for Dirigibles, Showing the Lights, Tackle and Winches Used in Bringing a Big Airship to Anchor: Note the Ground lights That Indicate the Direction of Wind ..." 

The other image of aviation interest is a chart of airplane types and how to identify them in silhouette--except that they are not in silhouette. Still it is a handy chat, and I reproduce it here: