The Smith patent is a short store ladder, fastened at about its center to the top of the base shelf, by means of a track and two rollers — the track being a part of the ladder — but adjusted as to height by means of a slot and screw arrangement. The base of the ladder is a roller or wheel, resting in the groove of a metal piece on the floor. In operation, the ladder runs backwards and forwards on two fixed tracks, from neithér of which is the weight of the man at any time wholly withdrawn. Nor has the weight of the man anything to do, except incidentally, with the lateral propulsion of the ladder.

The Shickle patent is a fire escape. Shorn of the machinery for its propulsion laterally, it is said to rest wholly upon the rollers at its base. But it is evident that the machinery could not be operated without putting a substantial weight upon the roller at the top. Besides, like the Smith patent, the ladder is permanently and closely adjusted at two points, thus failing to utilize any advantage in operation that may come from the balancing of the man’s body, so as to change the center of gravity.

The Murray patent is a store ladder whose weight is wholly upon the rollers upon the floor or base shelf — the upper fastening being a loose one, by means of hooks intended solely to keep the ladder from tipping over. It differs from the Shickle ladder in that it is not perpendicular, thus giving room for base shelves, and also an inclination that makes climbing easier; and it differs from both the Smith and the Shickle patents in that, practically, it runs on only one track, utilizing the balancing of the man’s body to propel it laterally without friction. This new thought in the art of ladder making — the utilizing of the man’s weight to adjust the center of gravity — clearly was in the mind of'the inventor, (letters patent line 40 et seq.) and finds embodiment in the mechanical means adapted to that end.

It is not enough to say that the upper hook of'the Murray patent is identical with the upper fastening of the Smith and Shickle patents. They have some offices in common; but the hook has an office that the fixed rollers have not, the yielding itself, without destroying its usefulness, to the balancing motion of the man’s body.

It is not enough to say that the Smith ladder, sawed off at or near the upper rollers, would be the Murray patent. Smith did not, in fact, saw off his ladder. But had he done so, preserving the mechanism of the fastening at the upper end, his ladder would have been unyielding to the balancing of the man’s body, and therefore would not have accomplished both the mechanical and the practical purpose that Murray achieved. We find from all this, that in the Murray patent there is conception of a new idea, together with its embodiment in appropriate mechanical form, substantially unanticipated, useful, and possessing the quality of invention. The decree of the Circuit Court will therefore be reversed, with the direction to the Circuit Court to enter a decree in complainant’s favor for an injunction and an accounting.