"Although Brewster patented the kaleidoscope in 1817 (GB 4136), a copy of the prototype was shown to London opticians and copied before the patent was granted.

"Although Brewster patented the kaleidoscope in 1817 (GB 4136), a copy of the prototype was shown to London opticians and copied before the patent was granted. As a consequence, the kaleidoscope became produced in large numbers, but yielded no direct financial benefits to Brewster. It proved to be a massive success with two hundred thousand kaleidoscopes sold in London and Paris in just three months." These days you should promote any invention as soon as you get patent pending. But I can see why Wright brothers we're suspicious back then. Other major failures we're early concentration to military sales and not taking competition seriously. Military sales are take it or leave it, you either win big or nothing. If some conservative major gets assigned to deal with the purchase and you are sellign something really new, the sale might be doomed before you start.