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The whistle requires [[overwritten]] 3 [[/overwritten]] 6 times the pressure and blows 1/3 as often hence the ratio of the power is 18 to one.
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[[page number in pencil]] 53 [[page number]]
Professor Caswell informs me that on his return from Europe The ship was unable to procure a pilot because its position could not be ascertained by the firing of the cannon or The sound of the steam whistle though they were heard
The difficulty of determining the direction of sound is shown by the convergence