- It contained water, rather than the acids conventionally employed in storage batteries
- its electrodes were magnesium and cuprous chloride, rather than zinc and silver chloride.
The Court recognized that when a patent claims a structure already known in the prior art that is altered by the mere substitution of one element for another known in the field, the combination must do more than yield a predictable result. 383 U.S. at 50-51. It nevertheless rejected the Government's claim that Adams's battery was obvious.
The Court relied upon the corollary principle that when the prior art teaches away from combining certain known elements, discovery of a successful means of combining them is more likely to be nonobvious. Id. at 51-52. When Adams designed his battery, the prior art warned that risks were involved in using the types of electrodes he employed. The fact that the elements worked together in an unexpected and fruitful manner supported the conclusion that Adams's design was not obvious to those skilled in the art.