There were other inventors, however, who sought Congressional contracts for everything from backpacks to musket tools. In the autumn of 1775, Captain John MacPherson proposed to Congress that he had developed a method which could "take or destroy every Ministerial armed vessel in North-America" and proposed that he try out his theory in and around Boston Harbor. Washington, however, got a second opinion from his artillery commanders that determined " in as much as he set out upon wrong principles, the Scheme would prove abortive."
Another inventor, Joseph Belton, even proposed in April, 1777 that he could manufacture a musket with a sliding lock and superimposed loads capable of firing "up to sixteen or twenty [balls] in sixteen, ten, or five seconds of time."
"make a Machine by the help of which, I will carry a loaded cannon, two or three miles up or down any of our harbours without any other assistance, and all the way there should appear nothing above the surface much larger than a man's hat and...would wholly descend under water for some time, and by expanding, would rise to the surface at pleasure, and by this means, to avoid any discovery when I had arrived within an hundred and fifty, or two hundred yards of a Ship, I could descend under the surface and go alongside of her bottom against which, I could discharge the cannon, that should be prov'd large enough to send a ball through any ship's side."
There is no evidence that Belton's theories of underwater gunnery were any sounder than MacPherson's, nor yet that he ever developed even a working prototype of his invention. A close reading of the Belcher Journal, however, indicates that he, too, should be listed among the inventors of the era who, like Bushnell and Belton, experimented with submarine warfare.