Slayter & Co. v. Stebbins-Anderson Co. (31 F. Supp. 96, 1940)

WILLIAM C. COLEMAN, District Judge.

This is a suit for infringement of a patent relating to a method for heat insulation of buildings, issued to one Games Slayter and by him assigned to the present plaintiff, Slayter & Company. The patent is known as reissue patent No. 19,929, reissued April 14th, 1936, upon application for reissue made January 22nd, 1936. The oi-iginal Slayter patent No. 1,728,837 was issued September 17th, 1929, on application filed September 30th, 1927, and was held invalid by the Circuit Court of Appeals for the Seventh Circuit in Therm-O-Proof Insulation Co. v. Slayter & Co., 80 F.2d 557. The reissue patent, however, was held valid and infringed by the District Court for the Southern District of New York in Slayter & Co., v. United States Insulation Corp., 20 F.Supp. 376. An appeal was taken but dismissed on appellant’s motion, 2 Cir., 94 F.2d 41. There is no privity between the defendant in either of these cases and the defendant or the intervener in the present case. The present defendant, Stebbins-Anderson Co., Inc., is a Maryland corporation and is engaged in the installation of rock wool for insulating buildings, the wool which it uses being manufactured by the Philip Carey Manufacturing Company of Cincinnati. Ohio, and this company has assumed the defense of this action on behalf of the defendant. The intervener, the Standard Lime & Stone Company, also a Maryland corporation, is a manufacturer and seller of unpatented rock wool for insulation. Its petition for intervention was granted upon a showing that this company and the Philip Carey Manufacturing Company manufacture and sell substantially similar unpatented rock wool; that such is installed by it and its customers in Baltimore and various other places, and by defendant and other users of rock wool manufactured by the Philip Carey Manufacturing Co.; that there is now pending against it in the United States District Court for the Northern District of Illinois, Eastern Division, a suit instituted by the present plaintiff since the institution of the present suit, alleging infringement of this same reissue patent of plaintiff; that the complaint in that Illinois suit is, except for changes in names and allegations as to venue and the like, identical with the complaint in the present suit; 'and that the defenses and issues in both suits are the same.

The necessary ' jurisdictional requirements are satisfied. Both the defendant and the intervener, hereinafter spoken of collectively as the defendants, deny both validity and infringement of the patent. By way of further defense, defendants assert that plaintiff is barred because of suppression of facts in the case which it brought, and in which it was successful in New York, namely, Slayter & Co. v. United States Insulation Corporation, supra. Also, defendants have filed a counterclaim by which is sought, in addition to. a declaratory judgment that the patent is invalid and not infringed,, an injunction against; and damages for maintaining an alleged unlawful system of licenses by using the patent to maintain, for a limited number of licensees, a monopoly in the manufacture and sale of unpatented material.

The invention embraced in the patent in suit is stated in the specifications as relating to a “method for heat insulating buildings and the like, and refers more particularly to an improved process by means of which houses or other buildings already standing, can be conveniently, economically and efficiently heat insulated although the invention in certain of its broader aspects is not limited to the heat insulation of buildings already constructed.” Another advantage claimed for the invention is “to provide a material which Can be economically produced and applied in the walls of the building in the carrying out of the method and which in addition to its heat insulation qualities will be fire resisting.” The single claim of the patent, however, is a method and not a product claim, and is as follows: “The method of building a wall whereby to increase the insulating and fire-resisting properties thereof without undue added weight, which method comprises utilizing spaced apart walls of a building previously constructed as a form for receiving heat insulating material, providing openings to afford access to the air spaces between said spaced apart walls, inserting the outlet end of a conduit through said openings, and pneumatically forcing through the said conduit a finely divided but not powdered heat insulating and fire-resisting material, said material being substantially free from dust and of low specific gravity and of a size to provide a large body for the amount of weight and substantially devoid of free moisture content whereby said wall is heat insulated and rendered fire resistant without bulging or damage to the surface thereof or to decorations thereon.”

Analyzing the claim, it will be seen that it calls for a method of (1) pneumatically forcing through (2) openings made in the inner or outer walls of the building, to afford access to the air spaces between such walls, (3) certain heat insulating material into such spaces. The particular material specifically described in the specifications of the patent consists of “corn cobs and paper in a ratio of one-half cubic foot each or by weight 9 lbs. of corn cob to 2 lbs. of paper, this being mixed with 9 lbs. of plaster of Paris and 2 oz. zinc chloride, lime or other suitable fungicide. The finely com-minuted corn cobs and paper are mixed with the plaster of Paris and the zinc chloride in a machine which is not described in detail but made the subject matter of a separate application, and sufficient moisture is added to permit the handling of the material without unnecessary dust. The moisture content, however, is limited with reference to the self-absorption quality of the plaster of Paris; that is, the plaster of Paris being dehydrated gypsum, it will absorb up to 15% of its weight, and the moisture content of the insulating material should not materially exceed such 15% of the weight of the plaster of Paris content.”

The original Slayter application contained not only process claims, that is, claims for a “method of heat insulating buildings”, but also product claims for “heat insulating material for buildings.” However, the Patent Office rejected all product claims, and the original patent No. 1,728,837 was allowed with a single method claim, the text of which is identical with the single claim of the reissue patent which is now before us, except that instead of the last clause beginning with the words, “and pneumatically forcing through the said conduit”, the original claim contained the following: “and forcing through the said 'conduit a com-minuted heat insulating material, said material being of sufficiently light weight, and void of free moisture content of sufficient amount to cause bulging or other injurious effects upon the exposed surfaces of said walls.” On December 21st, 1935, this claim was held invalid by the Circuit Court of Appeals for the Seventh Circuit in the case of Therm-O-Proof Insulation Co. v. Slayter & Co., supra, on the ground that it was too vague and indefinite in its wording, and also lacked invention. The New York suit, also previously referred to, brought by the. present plaintiff, Slayter & Co. v. United States Insulation Corp., supra, had been instituted on May 31st, 1932, that is, prior to the decision in the Seventh Circuit. Following this decision, the plaintiff, as has already been explained, applied for and obtained on April 14th, 1936, the reissue patent, and the New York litigation proceeded with respect to this patent.

Attention should also be directed to the fact that the specifications of the reissue patent are identical with the specifications of the original patent, with the single exception that the following sentence has been added to the description of the insulating ipaterial: “A material so prepared will be found to weigh not more than approximately 20 pounds per cubic foot.”

Taking up the question of infringement, the proof is clear that the present defendants do not infringe plaintiff’s patent, because defendants use rock or mineral wool in their process, which is not, in our opinion, to be treated as the equivalent of the material specified in the Slayter patent. We find that the two materials are different in (1) character, both chemical and physical, and (2) method and immediate result of application.

Mineral wool is a common, generic term, often used synonymously with rock or glass wool which, more correctly speaking, are two types of mineral wool made in this country. The more common kind is glass wool, which is obtained by mixing certain kinds of stone with molten slag from blast furnaces, and converting the whole mass into a fibrous state. It is free from iron. The appearance of the finished product is very much like wool, being soft and fibrous. It appears in a variety of colors, but is more often white, although some times yellow and gray, and occasionally quite dark. The color, however, is no indication of its quality. The other kind, — rock wool, — is made from granite rock' raised to 3000° F. and is free from sulphur. It is the only true manufactured “wool”. It has the same general appearance as that made from- slag and is white. Both of these materials consist of a mass of very fine, pliant but inelastic, vitreous fibers, interlacing in every direction and forming an innumerable number of minute air cells. Their great value in the insulation of buildings lies in the number of air cells which they contain, their consequent non-conduction of heat and fire-resisting qualities. In wool made from common slag, 92% of the volume consists of air held in minute cells, while in the best grade the proportion of air reaches as high as 96%. This confined air makes it one of the best, if not the best, of the non-conductors of heat. Aside from these qualities, it is very durable and contains nothing that can decay or become musty. See Kidder-Parker Architects’ & Builders’ Hand Book, 18th Ed. (1931), pp. 2024-25.

The Standard Chemical & Technical Dictionary, by H. Bennett, (1939), defines mineral wool' as meaning slag wool and rock wool. It defines slag wool as “an artificial product of the blast furnace made by blowing air through slag; gr.-yel. filaments; used in packing and insulation.” It defines rock wool as “an insulating material made from argilaceous lime stone”, argilaceous meaning like clay in substance. It defines glass wool as “very fine strands of glass, resembling wool in appearance, used in insulation.” One or more of these types are often described as being “nodulated”, which means that they are composed of .lumps or nodules. Also, there are two other types, (1) granulated rock wool, and (2) granulated rock cork. The first of these is manufactured by causing a blast of air or steam to impinge upon a molten stream of rock, which fiberizes it. The resultant loose material is then passed through a thresher to sub-divide it, and the sub-divisions are then rolled into granules by passing the material through a rotating cylindrical screen. The ' other material just referred to, namely, granulated rock cork, is nothing but rock 'wool mixed with an asphalt binder and formed into sheets, after which these sheets, or the trimmings therefrom, are ground up.

It is at once obvious that plaintiff’s material, as specified in the patent, has none of the aforegoing characteristics of any of the various kinds of mineral wool. It consists ‘.of corn cobs, comminuted or chopped up, .mixed with plaster of Paris, zinc chloride and water, the plaster of Paris being dehydrated gypsum. Mineral wool fibers are non-inflammable. The corn cobs and com-minuted paper of plaintiff are inflammable. Mineral wool is a homogeneous material, its fine interwoven fibers being entangled together, forming a light material, almost woolly in texture, of a uniform nature.; whereas the plaintiff’s material is a non-homogeneous mixture, having somewhat the appearance of chicken-feed. Mineral wool weighs approximately 5 to 9 pounds per cubic foot, while plaintiff’s material is much heavier, averaging 17 to 20 pounds per cubic foot.. Mineral wool contains no free moisture, while Slayter’s material contains, according to the patent specifications, moisture not materially in excess of 15% of the weight of the plaster of Paris content, which, however, was increased to 50% or 60% by Slayter’s own practice in producing the mixture and blowing it damp, in order to avoid dust. The individual fibers in mineral wool are solid, whereas the com-minuted corn cobs in Slayter’s material are cellular. . Thus, from- both a chemical and physical point of view, it is too clear to require further analysis that the two materials-are entirely different. Therefore, although Sláyter in his specifications does not restrict himself to the particular material described, stating that “while I have described one material and one method of applying it, I do- not wish to limit the method to the particular material mentioned, except as ultimately set forth in the claim,” such a saving clause cannot in law make something an equivalent which is not, in fact, an equivalent, or permit Slayter to read into his patent, as a substitute or alternative material, something which is not even remotely suggested by his specifications. Obviously, it does not suffice to say that the two materials are equivalents because they produce identity of result with respect to their insulating qualities.

In addition to being essentially different in their chemical and physical properties, the method and immediate result of applying the two materials are also essentially different. Slayter’s material is damp when blown, and when put in place it cakes or “sets”, due to the chemical change resulting from the inter-action of the plaster of Paris and. the water, forming gypsum; that is to say, it “sets”, just as does plaster in a cast or concrete in a form. In other words, a chemical reaction takes place and produces a partially solid mass. On the other hand, mineral wool is entirely dry at all times.- No water is applied to it-in the blowing. It undergoes no chemical reaction. No change whatsoever takes place in it during its application to, or after it is placed in, a wall. It does not “set” or harden.

Slayter’s claim begins with the phrase “the method of. building a wall * * * ” etc. This serves to emphasize the difference between the Slayter and the defendants’ material, for the walls of-a building may be said to be a “form” for receiving the Slayter material, akin to a form constructed for .receiving poured concrete. In the case o'f both the Slayter material and the concrete, the material can properly, be said to “set” in the form, but nothing of this kind takes place, when the defendants’ material is blown.

'In addition to all of the aforegoing, perhaps the most conclusive evidence that the two materials are not equivalents is to be found in the' testimony of Slayter himself in the present case, to the effect that he well knew the properties of mineral wool at the time he was working upon his alleged invention, but rejected this material because he found it unsatisfactory for the attainment of his objectives.

The evidence in the present case discloses that the kind of mineral wool used by the United States Insulation Corporation and found to infringe in the New York suit, Slayter & Co. v. United States Insulation Corp., supra, if not identical with, was at least substantially the same as, the mineral wool used by the present defendants.

This Court thus finds itself in disagreement with the finding of Judge Woolsey in the New York case with respect to infringement. Counsel for the defendants here have strenuously urged that Judge Woolsey would not have found as he did had it not been for suppression of the complete facts on the part of the plaintiff in the course of the proceeding before him. We find it unnecessary, however, to go into this argument. Suffice it to say that at least this much is true, as appears from the testimony and admissions in the present case, namely, that, for whatever reason, Judge Woolsey was not afforded the same opportunity as has been afforded this Court, to make a thorough, visual examination and comparison of the materials involved in the litigation, including the opportunity to witness the manufacture, in open Court, of the material called for by plaintiff’s specifications, precisely according to the specified formula.

The Patent Office had found that there was no invention in Slayter’s material, and therefore it rejected his product claims. In the litigation in Illinois, culminating in a finding by the Circuit Court of Appeals for the Seventh Circuit that Slayter’s original patent was void (Therm-O-Proof Insulation Co. v. Slayter & Co., supra), infringement was conceded, even though it appears that the mineral wool used by the defendant in that case was substantially the same as the mineral wool used by the present defendants. So, little help is found in the Illinois decision on the specific problem to which we are now addressing ourselves. Turning then, again, to Judge Woolsey’s opinion, it appears that after resting his finding of validity upon the fact, as he found, that what Slayter had done was entitled to the dignity of a patent in that he had combined with old elements an insulating material which was new, namely, had devised this material and combined it successfully with old methods of installation to achieve a new and very useful result, he proceeded to treat the Slayter material and mineral wool as one and the same thing through what he defined as “commercial evolution”, based, as he states, upon “wide commercial success of Slayter’s invention” [20 F.Supp. 380], which clearly is not supported by the evidence in the present case. On this point Judge Woolsey said, and we quote at considerable length from his opinion (20 F. Supp. at pages 379, 380) :

“X. It was with his insulating material, therefore, that Slayter turned the scale in his favor, cf. Dow Chemical Company v. Williams Bros. Well Treating Corporation [10 Cir.], 81 F.2d 495, 497, 498, Tolfree v. Wetzler [3 Cir.], 25 F.2d 553, 554, and, although the steps which he claims for inserting it into the spaces between the inner and outer walls of houses are old, he is entitled to a patent for his ‘method of building a wall’ with that material, of which the commercial success is decisively corroborative of my opinion that by his conception as embodied in his patent he has added something of value to the art of insulation.

“For, if the question of patentability be deemed to be nicely balanced in this cause, the casting consideration in determining that issue is the commercial success of Slayter’s material which was prompt and considerable.

“Some fifteen other houses were satisfactorily insulated with plaintiff’s material soon after it was devised, and many important companies promptly took out licenses under Slayter’s patent. Among the licensees were such companies as JohnsManville Company, Eagle-Picher Lead Company, Grand Rapids Plaster Company, Tennessee Rock Products Company, Capitol Lime & Cement Company of Baltimore [apparently a misnomer for the present intervenor-defendant], General Insulating & Manufacturing Company, and — latest of all — the United States Gypsum Company, owner of the Balduf patent.

“The Grand Rapids Plaster Company used Slayter’s material up to some time in .1935, when mineral or rock wool was made in lighter weights and nodulated so that it could be blown. Whereupon it, and also nodulated glass wool, a new product, came to be used by many of the plaintiff’s licensees in their house-blowing operations under the patent, and, as these materials achieve the same purpose as Slayter’s material in substantially the same way, they have now practically superseded it for such use. Without any attempt at a thorough census, the evidence shews that upwards of 87,000 houses have been ‘blown’ by plaintiff’s licensees since Slayter secured his patent.

“XI. When in one of the useful arts many different men are engaged in seeking the same or a similar objective for its improvement, it is the man who first takes the final forward step which causes the embodiment of his conception — whether it be a process, a product, or a device— to emerge, by reason of its intrinsic merit, from the twilight zone of experiments and approximations into the sunlight of commercial success, who is entitled to an inventor’s status. The Barbed Wire Patent (Washburn & Moen Mfg. Co. v. Wiler), 143 U.S. 293, 12 S.Ct. 450, 36 L.Ed. 154; Magowan v. New York Belting & Packing Co., 141 U.S. 332, 343, 12 S.Ct. 71, 35 L.Ed. 781; Consolidated Safety-Valve Co. v. Crosby Steam-Gauge & Valve Co., 113 U.S. 157, 179, 5 S.Ct. 513, 28 L.Ed. 939; Webster Loom Co. v. Higgins, 105 U.S. 580, 591, 26 L.Ed. 1177.

“Slayter took his final forward step in the art here under discussion and, consequently, the plaintiff, as his assignee, is entitled to protection in the practice of his patent.

“XII. The wide commercial success of Slayter’s invention has led, as above mentioned, to the contrivance, through the operation of what may be called commercial evolution, of insulating materials— nodulated rock, mineral, or glass wool— which have proved convenient and adequate equivalents for the material of his patent.

“Nodulated mineral, rock, or glass 'wool is now used for blowing insulation by most of the plaintiff’s licensees.

“Mineral wool is used by the defendant company which is not licensed by the plaintiff.

“The use of these materials by the plaintiff’s licensees is commercial proof that they are equivalents to — perhaps, in some ways, improvements on — the insulating material of Slayter’s disclosure. Thus they conclusively bridge the gap between the plaintiff’s patent rights and the defendant’s infringement thereof, cf. Fleischer Studios v. Ralph A. Freundlich, Inc., (D.C.) 5 F.Supp. 808, 809, for by Slayter’s specifications he expressly did not limit his monopoly to his disclosed insulating material, but left open the question of equivalents, cf. Paper Bag Patent Case (Continental Paper Bag Co. v. Eastern Paper Bag Co.), 210 U.S. 405, 418, 28 S.Ct. 748, 52 L.Ed. 1122, and his claim was bfoad enough to cover the nodulated mineral or rock wool used by the defendant, which was not a substance known and used in that form for insulation when Slayter got his patent.”

That Slayter’s material was neither commercially successful nor may properly be treated as the precursor of the mineral wools that subsequently did become commercially successful for insulating purposes, is clearly demonstrated by the evidence in the present case of what Slayter and the licensees under his patent actually did.

Shortly after the original Slayter application for a patent was filed on September 30th, 1927, Slayter licensed the so-called Kalkite Company to manufacture and to install, by pneumatic power, the material described in his application. This company satisfactorily insulated some fifteen houses with this material, but this soon ceased to be profitable and the business was discontinued. Later, but before his patent was actually issued, Slayter started another operating company, known as the Indiana Insulation Company. The Grand Rapids Plaster Company manufactured Slayter’s material for this Indiana Company, and a license issued May 17th, 1930, to the Grand Rapids Company was apparently the first, or one of the first, licenses granted under the patent. Meanwhile, however, in 1928 one Henry J. Burt, who had been employed by the Kalkite Company for some time previously, started business for himself as the Wall-Fill Company, and became associated with the Johns-Manville Company. For a number of years thereafter, Burt was employed to do installation work by the JohnsManville Company with rock wool which that company furnished him, installing the material by pneumatic power in the same way that he had previously installed Slayter’s material when he was with the Kalkite Company. Later, when the JohnsManville Company took a license from the plaintiff under its patent, the Wall-Fill Company received a sub-license from the Johns-Manville Company and insulated approximately 7,000 houses by pneumatic power with Johns-Manville Company’s rock wool; and the latter company has, through its various customers and dealers, insulated, up to the present time, some 80,000 houses in the same manner.

This evidence is similar to the evidence referred to in Judge Woolsey’s opinion, as to which he says, (20 F.Supp. at page 380) : “Without any attempt at a thorough census, the evidence shows that upwards of 87,000 houses have been ‘blown’ by plaintiff’s licensees since Slayter secured his patent.” But we cannot agree, upon the evidence that has been presented to us, with the subsequent statement in Judge Woolsey’s opinion, included in the quotation already given, that the use of the Johns-Manville rock wool, or the wool of any of the other contemporary licensees of the plaintiff, was an equivalent of, or an improvement upon, the insulating material of Slayter’s disclosure. We have already pointed out how distinctly different the materials are in chemical and physical characteristics, as well as in operation. Allusion has also been made to the fact that Slayter himself recognized that mineral wool was well known at the time of his invention, but he discarded it as not being satisfactory for his purposes. It then seems unnecessary to go into an analysis of the extent to which mineral wool had previously been used for insulation purposes. In the present case, manufacturers of mineral wool testified that material, substantially the same as that used today, was known and in use for insulating purposes long prior to Slayter’s invention. Indeed, it is stipulated in the present case that, over twenty years ago, mineral wool was applied as a filler to the hollow spaces between the inner wall of lathe and plaster and the outer wall of sheathing, of at least two residences in Salem, Virginia. While it is true this mineral wool was not applied pneumatically, the method of application is of more importance with respect to the question of validity of the Slayter patent which is hereinafter considered, than with the immediate question of infringement. Likewise, it is stipulated that prior to 1926, mineral wool had been placed in the hollow walls of many other buildings, including the old mansion of George Washington, at Mt. Vernon, Virginia.

Summarizing the aforegoing, it thus appears that mineral wool and the Slayter corn cob and plaster of Paris combination are not equivalents. This means that Slayter’s patent, assuming it to be valid, must be limited to use of the material specified in the patent or to something that is, in fact, an equivalent thereto, and that, therefore, the patent is not infringed by the use of mineral wool. A different conclusion, namely, that the two materials are substantial equivalents, would of necessity result in finding that Slayter’s patent is invalid, because the claim and the catch-all clause of the specifications, hereinbefore quoted, are couched in such broad terms as to cover what was known and used in the same way for the same purpose in the prior art.

There still remains the question whether the Slayter patent is valid, even when restricted to the use of the particular Slayter material, or an actual equivalent. This question we will now consider because, although it would be sufficient, having found non-infringement on the part of the defendants, to dismiss the bill of complaint on this ground alone, nevertheless, in view of the pleadings and the extent and character of related litigation, and the importance to the large industry affected, we deem it desirable to pass upon the question of validity also.

Defendants claim that the Slayter patent is invalid on at least five grounds: (1) the claim is anticipated by the known processes of blowing mineral wool, granulated cork, concrete, etc.; (2) Slayter’s method involved no invention over these known blowing processes, which if not literally anticipatory, were fully analogous; (3) the patent claim is broader than, and not responsive to or supported by the method prescribed in the specifications; (4) the patent claim is vague and indefinite; (5) absence of proof of any “inadvertence, accident, or mistake” in the original patent as required by the reissue statute, 35 U.S.C.A. § 64, and hence no justification for the reissue patent in suit.

Considering these grounds in the order named, what has heretofore been said under the subject of infringement would appear tó be sufficient proof of the soundness of the first two grounds. In addition, testimony was introduced which was undisputed, showing that the process of granulating and blowing mineral wool into storage bins or similar confined spaces, was known long before Slayter’s alleged date of invention, December, 1926, and also, that this wool was substantially the same in its physical characteristics as the material used by the defendants today. Also, there is uncontradicted testimony that the same process as that employed by defendants was employed at Newport News and elsewhere, long prior to Slayter’s alleged invention, for the purpose of insulating vessels, the only difference being that granulated rock cork was used instead of granulated mineral wool. In Slayter & Co. v. United States Insulation Corp., supra, these operations were distinguished from Slayter’s method on the ground that “granulated cork is not an equivalent, because it is not fire resisting or substantially free from dust.” 20 F. Supp. at page 379. The uncontradicted testimony in the present proceeding, however, is quite the contrary, namely, that granulated cork is fire-resisting and not nearly as dusty as the Slayter material made in strict accordance with the patent specifications.

Furthermore, since 1914, the blowing, pneumatically, of various materials, including granulated cork, and packing such materials into confined spaces, has been fully disclosed, as evidenced by the prior art patents placed in evidence in the present proceeding. See particularly British patent No. 23,533 to Hugh Miller MacMillan, dated 1914. It was stated in the course of the present proceeding that this British patent, as well as numerous others presented herein, were not before Judge Woolsey in the New York case, among such others being the patent No. 1,478,865 to Carl Weber issued December 25, 1923, which comprised a method for injecting plastic materials into confined spaces by air pressure. See, also, Powers-Kennedy Contracting Corp. v. Concrete Co., 282 U.S. 175, 51 S.Ct. 95, 75 L.Ed. 278.

From the aforegoing it is clear that if there is any claim to novelty in Slayter’s idea, it must be restricted to his particular corn cob and plaster of Paris combination. Judge Woolsey held that this was new, and that it was for devising this material, and combining it successfully with old methods of installation to achieve a new and very useful result, that Slayter was entitled to patent protection. But the evidence produced in the present case makes untenable a finding that Slayter achieved a “new” result, or that it was “useful" in any appreciable degree, because, as we have seen, his material became, almost immediately, commercially unsuccessful, and it was only through the substitution of an entirely different material, mineral wool, that the combination became useful. It is, of course, true that a combination of elements, all of which are old, may, nevertheless, be patentable, if the result of such combination is, in fact, both new and useful. A fortiori, the same is true if one or more of the elements in combination are new. But, as has already been shown, the extremely limited commercial use to which Slayter’s method was ever put, scarcely spells commercial utility or success. However, even if such be assumed, other patentees, long prior to Slayter, devised material for insulating purposes which may well be considered as equivalents. We agree that the American patent to Balduff, No. 1,-723,989, and the German patent to Orlovsky, No. 378,196, disclose doubtful equivalents. However, two prior American patents, apparently not before Judge Woolsey, namely, to Clayton, No. 369,099, issued August 30, 1887, and to Brownell, No. 1,-737,957, issued December 3rd, 1929, on application filed November 2nd, 1926, that is, antecedent to the application