inner tube C, has also within it a diaphragm, N, toward its upper portion, and that there is a central air passage, 14, in this diaphragm or disk. Also that the said tube, C, is perforated beneath the said diaphragm, N, but is whole above the same except about the top where there are large openings or holes, 15. Now, one of the results of this construction is the supply of a flame centrally about the top of the said burner tubes. If some provision of this kind were not made combustion would occur only in a ring, as it were, about the top of the combustion chamber, and there would be a dead cold spot in the middle of the ring. This I overcome by the construction shown, and thus diffuse the flame and heat over the entire surface above the burner chamber. This occurs by reason of air flowing through the central hole, 14, which this meets with the products of combustion which flow inward from the combustion chamber through holes, 15, into what may be termed a partial vacuum within the top of the inner combustion tube. The fresh heated air fed through the said hole, 14, promotes and completes combustion in this central space."

The means for producing the result are quite unlike those of the Ruppel in suit. Blackford No. 538,638 is shown below:

"Now, having reached the top of the lower burner section, I provide an upper section consisting of two numerously perforated combustion tubes, H and K, seated upon the shouldered and flanged upper extremities of the tubes A and B, and about the top of the wick, C, on the said shoulders.

"Two diaphragms-12 and 13-span the inner tube, one near its bottom and the other toward its top; and both tubes have central air passages through them, but the upper one considerably smaller than the lower, thereby allowing enough air to pass through to supply the needs of combustion centrally in the top of the burner at a point just above the top of said combustion tubes, and at the same time checking back the air so as to cause it to flow freely to the combustion chamber between tubes H and K through the

perforations in K. The lower diaphragm-12-also serves as a heat deflector to protect the wick chamber beneath from becoming excessively heated.

*

"By the use of the tubes H and K and the associated parts, combustion, in fact, does not really take place at the wick except in starting the burner, but a vapor is evolved, which burns between said tubes, and a perfectly blue flame is assured at the top of said tubes while the wick remains unconsumed and will last for an entire season or longer."

Here both diaphragms are perforated, and there is no cap. The defendant states that the inner tube does not feed air above the upper diaphragm. The diagrams in both Blackford patents, and the absence of any limitation to the perforations in the tube, do not confirm this state

ment.

Lannert & Jeavons, 1891, patent, No. 464,076, is shown by Figure 1:

This shows two perforated tubes, one within the other, to avoid the escape of vapor through the perforations, "causing disagreeable odors in the room, and robbing the burner to that extent of its fuel." There are employed "deflectors, which extend around about the sides of the burner tubes, as shown, and serve to convey the escaping vapor or gas back into the burner chamber to be consumed." There are three such deflectors. It seems that the mechanism is such that these deflectors are deemed necessary, and their importance is emphasized in the specification. Within the inner tube is a "combined air and flame deflector, as well as a shield for the burner." "In form it has the shape of a section of a cone, its narrower portion resting on the top of the inner burner tube, and its wider portion extending outward a sufficient distance to protect the combustion chamber between the tubes." The head has parallel slots formed about its sides, and to divert the air through the slots the top of the head is closed, but the bottom is open. "The conical-shaped deflector tube, h', extends into the space within the inner tube a greater or less distance-say half way the length of the

tube-and is open at its bottom, so that a free air passage is formed through the same end through the lateral slots, h3, in the head." It should be observed that where the deflector rests on the inner tube it closes it, so that no air beyond such point of closing can pass from the inner tube to the outer tube or to the flame, the air for feeding the flame above such point passing through the cone. In the lower part of the inner tube, and just below the cone mentioned, is the deflector, E, an inverted truncated cone. Its base spans the inner tube, and is entirely open, as is the lower and smaller end. Necessarily these two cones placed within the inner tube limit the air passing to such tube, but in fact the upper cone itself is an imperforated inner tube with slots entirely above the combustion chamber immediately under the cap.

It is considered that in no proper sense does this structure show "two walls with a space between them spanning the bore of the inner of said perforated tubes, and forming an air chamber at the upper end thereof." The most that can be said is that the two conical deflectors are so inserted into the inner tube that, together with the cap, they occupy such portion of the inner tube as to limit the access of air to it. The multiplicity of parts, tubes, deflectors, and cones, exterior and interior, bear but an imaginary similitude to the structure suggested by the patent.

The next reference is to the letters patent issued to Mummery, 1896, No. 563,788. Figure 1 illustrates it:

This has two concentric combustion chambers, simultaneously operated, formed by the perforated walls. There are three tubes that have air chambers formed by a perforated diaphragm and perforated cap. The whole interior of the inner tube is called an air chamber, and is marked "F," "into which the air may freely pass through the openings A', B', in the holder, A, and vaporizer, B." After providing for a cap over the inner tube "to engage the upper ends of the corresponding foraminous walls," and for a horizontal partition "intermediate the upper and lower edges" of such walls, it is stated that this partition is "constructed with orifices, h, preferably elongated, through which the air may freely pass into the regions of the chambers thereabove," and that the cap is "provided with suitable perforations or orifices, as at e, preferably elongated." Then follows this statement:

"These partitions, H, H1, H2, as indicated more especially in Fig. 5, are constructed with orifices, h, preferably elongated, through which the air may

freely pass into the regions of the chambers thereabove. The caps, E. E1, are also provided with suitable perforations, or orifices, as at e, preferably elongated. The partitions, H, H1, H2, are employed for the purpose of holding the respective parts adjacent thereto in place.

"It will be understood that when the burner is in use the foraminous walls on the inner and outer peripheries of the respective combustion chambers become very highly heated, and these partitions prevent all liability of the warping of said walls in consequence of the heat holding the parts securely in position.

"It will be obvious that air is admitted into the respective combustion chambers through the surrounding foraminous walls on both the inner and the outer peripheries of each chamber, the bulk of air being admitted into the combustion chambers through the lower perforations of the walls.

*

"The upper orifices, e, in the caps, E, E1, are preferably elongated, as before stated, so as to let the air that may accumulate in the upper portions of the corresponding chambers, F, F1, more freely escape. These caps, E, E1, E2, are employed chiefly to deflect or hold down the air to cause its passage more efficiently through the foraminous walls of the combustion chambers. At the same time, in order to prevent an accumulation of dead air in the top of the air chambers and to prevent an undue deflection of the heat downward thereby, it is desirable to provide the slots therein, as above described, so that there may be a desired circulation of air therethrough to prevent the accumulation of dead air and to allow the heat to escape upward."

If this cap were imperforated, the interior tube would fall within the description of the claims of the Ruppel patent. It does not seem that there would be invention in placing the lower diaphragm higher up. But how about the perforations in the cap? The evident fact is that the holes in the cap might be so small as to render the cap substantially closed, and to force all the air through the side walls of the tube, or they might be so large as to allow the rising air to pass through the cap in quantity too large for the advantage of the combustion chamber. Jeavons, complainant's witness, testified:

"For its proper operation there should not be any appreciable volume of air passed through its top, as in such case rather combustion would occur immediately above it, and the heat from this combustion would tend to disassociate the carbon monoxide gas, and cause a yellow flame. Again, such heat would be evolved some distance below the cooking utensil, and it would not be so effective for the purpose of heating such utensil as in cases where the gas passes up and is consumed close to the bottom of said utensil. If the opening were a very small one, so that combustion resulting therefrom were very small, the device might work much the same as it does with the imperforated cap. If the opening through the cap were any appreciable size, it might not only rob the chambers at the upper end of the inner tube of the air that should be deflected outward into the rising gases, but it would induce a suction through its openings so that the gas rising from the combining chamber would flow inward to the chamber and meeting the air passing through the lower plate would burn in this chamber."

Mummery does not describe the size of the perforations in the cap, but they should be large enough "so that there may be a desired circulation of air therethrough to prevent the accumulation of dead air and to allow the heat to escape upward," and small enough "to deflect or hold down the air to cause its passage more efficiently through the foraminous walls of the combustion chambers." The specification would then mean, "Make the holes in the cap large enough to let off the dead air and heat, and small enough to dam back the air so that it will pass through the walls of the tube." Whether holes can be so adjusted as to let air

and heat escape, and yet keep air desirable for the combustion chamber from escaping at the cap, does not appear. However, it would seem that the perforations in the cap must be nicely related to the perforations in the diaphragm and side walls to get the desired balance, so that the right amount of dead air and the heat would pass out above, and a suitable amount of live air would take a lateral direction. Ruppel was not at the expense of perforating the cap, nor did he assume the task of deciding just how large holes would perform the office of letting out dead air and heat, and at the same time not let out live air that should escape elsewhere. He adopted a closed cap. If there is no advantage in this, why does the defendant adhere to the closed caps? Why does it not use the Blackford, Mummery, or similar structures? It is asserted by the learned counsel for the defendant in his written argument that the Ruppel upper chamber in the burner used, admitting air through its diaphragm, is in operation practically the equivalent of Morrill's burner, which has a solid plug in the upper end of the tube; the Ewert, 1887, burner, which has no cap, and an imperforated diaphragm at the bottom of the tube; and the Ewert & Mehling, 1890, burner, which has a closed cap, and no perforations in the upper end of the inner tube; and it is asserted, further, that actual demonstrations in this suit show that the function of these upper chambers is the same, that the result is the same, and that the Ruppel burner performs the same function with the same result, whether the diaphragm is open or closed, or whether its cap is retained or removed. It will be noticed that the Silver burner is not included in this statement. But several hours of observation of the Ruppel and Silver burners, side by side, shows no superiority on the part of the Silver, nor does the evidence disclose that it has practical advantage. The blue flame of one was not distinguishable from that of the other, either in color or steadiness, or other desirable characteristic. Yet it is urged that the Ruppel feeds. no air from the upper chamber to the combustion chamber, and that the Silver does. Here is apparent perfection of operation in two burners, each constructed according to the claims, the only difference in the burners being that the chamber in one is higher up than in the other, and the openings in the diaphragms are differently located. If there was no better result from the chamber composed of the perforated diaphragm and closed cap spanning the walls of the tube in the upper portion thereof, the parties, it is thought, would use the Ewert & Mehling burner, thereby saving the expense of a diaphragm and of the perforations in the upper part of the tube; or the Ewert, 1887, and save the expense of a cap and the perforation of the diaphragm. And if the Morrill is the equal of any, at least the expense of the solid plug is saved. The fact is that the complainant and defendant herein are not battling for the right to use this upper chamber described by the Ruppel claims without full knowledge of its utility and commercial advantage. The evidence of a considered and settled commercial practice persuades more than the experiments of experts, made for the purposes of the action, necessarily brief in duration, and not put into the ordinary. domestic uses for which the burners are designed.

It now becomes necessary to give attention to the lamp devices.