Popular Mechanics 1924 –
THE interesting little toy described in this article will, when placed in water, automatically dive and come to the surface again, repeating this performance, on an average, once a minute over a long period of time. It not only makes a very good toy for a boy but can be used also for advertising purposes. Placed in a glass tank and displayed in a show window, its actions will attract the attention and interest of passers-by, who will stop to wonder how it operates.
The mysterious submarine – Link.
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