Opinion of the Court. has been heretofore the greatest objection to reservoir-stoves of this class, namely, that the reservoirs would not heat with a direct draft. It will also be observed that, by this device of constructing the exit-passage below the top of the oven, I can at the same time by a direct draft heat the rear side of the oven and the reservoir, instead of wasting the heat by carrying it directly to the chimney. When the damper Q is closed, for the purpose of heating the oven, the gases of combustion will pass down the side vertical flues L L' and under the bottom of the oven, returning through a central horizontal flue to the central vertical flue K, from which they pass through the exit-flue E E', aforesaid. I am aware that cooking-stoves have been in use in which the reservoir has been incased or inclosed on all sides except the top by a kind of expanded flue, through which the gases of combustion are made to pass. The advantages of my plan over this device are twofold: First, it is much more economical, requiring far less material and labor to construct it; and, second, by confining the heat and gases of combustion to a small space at the bottom and rear of the reservoir, the contents thereof will be much more effectually heated than where the products of combustion are admitted to an extensive flue-space and permitted to rise and expend their heat at or near the top of the reservoir." The claims of the patent, the first 4 only of which are alleged to have been infringed, are as follows: "1. A diving-flue cooking-stove with the exit flue so constructed as to inclose on the sides and bottom the culinary boiler or hot-water reservoir B. 2. A diving-flue cooking-stove with the exit-flue constructed across the bottom and up the rear upright side of the culinary boiler or hot-water reservoir B. 3. A diving-flue cooking-stove constructed with an exit passage, F, below the top of the oven, and an exit-flue E E', in combination with an uncased reservoir, B, attached to the rear of the stove, and placed just above such exit passage, and so arranged that the gases of combustion, in passing through such exit-flue, will impinge upon or come in direct contact with said reservoir, substantially as and for the purposes herein before specified. 4. An exit-passage, F, constructed in the rear of a diving-flue cooking-stove and below the top of the oven, in combination with Opinion of the Court. an uncased reservoir, B, attached to the rear of the stove, the bottom of which reservoir is also below the top of the oven, and so arranged that the gases of combustion will come in contact with and heat such reservoir by, a direct draft from the fire-box to the smoke-pipe. 5. In a cooking-stove wherein the rear-end vertical plate, or a portion of the same, has been removed for the purpose of heating a reservoir placed in the rear thereof, the shieldplate w w, in combination with the uncased reservoir B and the rear-end vertical flues K, L, and L', substantially as and for the purposes herein before described and specified." The defendant's stove has three flues and an exit-passage below the top of the oven, and a reservoir, the bottom of which is below the top of the oven; but no part of the rear-end vertical plate is removed so as to allow the gases of combustion to come into direct contact with the front of the reservoir, nor is any of such plate employed as the plate w w of the patent, but there is a dead air-space between the rear plate of the flue and the front of the reservoir. The exit-flue is not a narrow one, carried across the middle of the bottom of the reservoir, as in the patent, but the products of combustion, on leaving the flue-space, pass into a chamber beneath the reservoir, the area of which is co-extensive with the entire surface of the bottom of the reservoir; and the vertical passage out of such chamber is not one outside of the rear of the reservoir, but is one in and through the body of the reservoir, and removable with it. In view of the earlier patents put in evidence, we are of opinion that the 4 claims in question must be limited to a structure in which the front of the reservoir has no air-space in front of it, and in which the exit-flue does not expand into a chamber at the bottom of the reservoir, and in which the vertical part of the exit-flue does not pass up through the reservoir. Under this construction there is no infringement of No. 3,815. Claim 1, in requiring that the exit-flue shall "inclose on the sides and bottom," the reservoir, requires, in the language of the text of the specification, that it shall extend "down the front, under the bottom and up the rear" of the reservoir; Opinion of the Court. and it does not admit of an air-space in front of the reservoir; nor is it limited to what is called a low-down boiler or reservoir. The Getz patent of 1840 shows an exit-flue passing under the bottom and up the rear side of a reservoir. The Spaulding or Paris patent of 1858 shows a diving-flue inclosing the bottom and one of the sides of a reservoir. Claim 2 is not limited to a low-down boiler or reservoir. If a stove with an exit-flue constructed across the bottom and up the rear upright side of a boiler or reservoir existed before, there was nothing patentable in applying such construction to a diving-flue stove. The combination of exit-flue and reservoir with which claim 2 is concerned has no patentable relation to the arrangement of the internal flues of the stove. The Getz patent of 1840 shows an exit-flue extending across the bottom and up the rear upright side of a boiler. In the Stewart patent of 1859 the products of combustion enter a chamber under the reservoir and thence pass off by a pipe embraced within the walls of the reservoir. The exit-flue of claim 2 must, therefore, be limited to one which passes under the bottom of the reservoir without expanding into a chamber substantially co-extensive with the area of the bottom of the reservoir, as in the defendant's stove and in the Stewart patent of 1859; and also to one in which the escape-pipe is outside of the rear wall of the reservoir and not within the reservoir, as in the defendant's stove and in the Stewart patent of 1859. Claim 3 adds to claim 2 only the feature of having the exitpassage or exit-orifice into the exit-flue, below the top of the There is no patentable relation between the combination of exit-flue and reservoir and the location of the exit-passage with reference to the oven, in view of the state of the art. In the Stewart patent of 1859 the exit-opening was on a level with the top of the oven and led into a chamber under the reservoir. In the Spaulding or Paris patent of 1858, and in the Bussey patent of 1865, the bottom of the reservoir was below the top of the oven. There was no invention in causing the gases to act on a low-down reservoir in the same way in which they had acted before on an elevated reservoir; and no invention in lowering the exit opening to correspond oven. Opinion of the Court. with the depression of the reservoir, even though the incidental effect was to heat by a direct draft, at the same time, the reservoir and the rear side of the oven. Claim 4 adds to claim 3 only the feature of heating the reservoir by a direct draft from the fire-box to the smokepipe. This, however, is only a statement of the effect produced in a structure made according to the first three claims. In the Getz patent of 1840 and in the Stewart patent of 1859 the exit-pipe was in the rear of the reservoir, and the gases were brought into contact with the bottom of the reservoir, and it was heated by a direct draft. There is really nothing in claim 4 beyond what is found in claim 3. "Our invention relates to that class of cooking-stoves in which a water reservoir is situated at the rear end of the stove; and it consists in the arrangement of the reservoir upon an extended support at the rear of the stove, so that an air-chamber, opening at its top into the air of the room, is left between the backplate of the stove and the front of the reservoir, thereby, protecting the front of the same from becoming burned out by being in direct contact with the heat from the fire. It also consists in a broad sheet-flue arranged under the reservoir, the heated air for which enters through a small passage in the back-plate of the stove, and, after circulating in said flue, passes out through the small opening in the rear thereof, all as more fully hereinafter set forth. Figure 1 is a longitudinal vertical section of our stove; Fig. 2 is a transverse vertical section of the same through the water-reservoir; Fig. 3 is a plan view of the reservoir; and Fig. 4 is a front view of the sheet-flue under the bottom of the reservoir. A represents the top plate of the stove. B is the oven; C, the water-reservoir; D, the centre one of the three flues of the stove ; and E, the exit-flue, located in the rear of the reservoir C. This reservoir is located upon a support therefor, which extends rearward from a point about half way between the top and bottom plates of the stove, and which may either be attached to or form part of the stove, and a sheet-flue, G, is provided in the same under the bottom of the reservoir C. The heat, entering this flue, Opinion of the Court. passes through the small centre passage a in the stove-back I. It is there spread and retained under the reservoir until it gradually ascends through the small passage or exit-flue E. By this con struction the rapid exit of the heated air from under the reservoir is prevented, and the heat, being retained under the bottom of the reservoir, causes the water in the same to become hot in a short time. The reservoir C is so arranged with respect to the |