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 particular purpose for which it was to be used, whether for screens, signalling, or other purposes.

As an example the "E" float may be cited. A demand had arisen for a smoke-producing device for use on board merchant ships to assist escape from enemy submarine attack. Commander Brock, with characteristic energy, in a very short space of time produced the "E" float, which for ease in manipulation by untrained operators and volume of smoke produced was probably unsurpassed by any subsequent device, and on the score of cheapness it undoubtedly held the field.

This store, which was in reality a triumph of pyrotechnic design, was in appearance so simple as to mislead some at least to whom greater insight might have been credited as to the ingenuity of its design. Counsel at a sitting of the Royal Commission on Awards to Inventors, described the float as "half-a-dozen or so drain rockets in a box." A remark which might be considered as accurate as to describe a clock as some pieces of metal in a box, were it not for the fact that the box in question contained no drain rockets, or anything resembling them more closely than one firework resembles another designed for quite a different purpose.

The requirements to be met were as follows: The apparatus was to be used by men whom by nature of their employment it was impossible to train individually, therefore its ignition must be simple and at the same time certain and quick in action, and carried on the float itself; a chamber had to be provided in which to as it were accumulate the smoke generated, which chamber had of necessity to have holes through which the smoke could issue. As the float had to be dropped after ignition from the deck of the vessel into the sea, and would consequently be submerged for a short time, these holes must be in some way sealed until the float rose to the