CAMPBELL V. THE MAYOB, ETC., OF NEW YORK. 603 �engineer of a steam fire-engine in use in the city of Troy for the pro- tection of property there against fire, and in the latter part of April, 1860, applied his invention in the form of a pipe leading from the discharge to the suction sides of the engine, with a globe valve be- tween. The invention was tried and operated satisfactorily, except that he thought that the passage was rather small. This engine, which was called the Arba Eeade, was continued in use with the in- vention upon it, Knibbs continuing to be the engineer. In January, 1862, the city of Troy procured another steam fire-engine, of sub- stantially the same pattem, to which, at the request of Knibbs, his invention was applied in the form of an opening through the par- tition between the discharge and suction sides of the pump, with a valve working to a seal as the opening through which the excess of water could be made to pass. This engine, which was called the J. G. Osgood, was put to use for the city, and the invention operated satisfactorily to Knibbs, as well as to others concemed. The tube to the Arba Eeade was made larger in February, 1863, and worked more satisfactorily to all. Knibbs thought of applying for a patent, consulted a soliciter of patents about it, and made application for the one that was granted May 13, 186e, without at auy time intending to abandon his invention to the public. In 1861,. and consequently more than two years before the application, the Amoskeag Manufac- turing Company made other steam fire-engines containing this inven- tion, which were sold and went into use, and from that time until after the application such engines were occasionally made and sold by the company, and perhaps by other manufacturera, and went into the customary use. This was done without the consent and allow- ance of Knibbs. �It is eontended that these uses and sales, either thoae with or those without the consent and allowance of Knibbs, will defeat the patenta This invention, like that in Elizaheth v. Pavement Go. 97 U. S. 126, could not well be experimented with and tested in private. Ite object was conuected with purposes in their nature public, and its practice waa necessarily somewhat of the same nature. The inven- tion was not essentially varied by the trials and use made, and was patented aceording to its features as first applied. Still, it was not -clear to the inventor that no changes or modifications would be nec- •essary, and necessary to be specified in the application for a patent, in order to obtain the full benefit'of orie. In this view the use by him as engineer, and by the city of Troy at hi& request, is deemed to have been experimental and allowable within the rule laid down in the case ��� �
