Where the infringer has sold or used a patented article, the
patentee is entitled to recover all of the profits.
Where a patent, though using old elements, gives the entire
value to the combination, the patentee is entitled to recover from
an infringer all the profits.
Where profits are made by using an article patented as an
entirety, the infringer is liable for all the profits unless he can
show, and the
Page 225 U. S. 605
burden is on him, that the profits are partly the result of some
other things used by him.
Elizabeth v. Pavement Co.,
97 U. S. 126.
Where the patent admittedly creates only a part of the profits,
the patentee is only entitled to that part, and he must apportion
the infringer's profits and show by reliable and satisfactory
evidence either what part of the profits are attributable to his
patent or that the entire value of the infringing article is
attributable to his patent.
Garretson v. Clark,
111 U. S. 120.
Congress has legislated, Rev.Stat., § 4921, with a view to
affording the patentee ample redress against the infringer, but the
general rule of law that the burden is on the one suing for profits
to show that they had been made applies.
The patent itself is evidence of the utility of the claim, and
an infringer is estopped from denying that it is of value.
Where the plaintiff patentee shows that profits have been made
by the use of his patent, but defendant proves that there were
other elements contributing to the profits, it then devolves upon
the plaintiff to apportion the amount of profits attributable to
the use of his patent.
Where the infringer, however, by commingling the elements,
renders it impossible for the patentee to meet the requirement of
apportionment, the entire inseparable profit must be given to the
patentee. In such a case, as in that of a trustee
ex
maleficio confusing gains, the loss should fall on the guilty,
and not on the innocent.
This rule applies even if the patented device infringed did not
preponderate the creation of profits. The owner of a small part of
a fund is equally entitled to protection as the owner of a larger
share.
While the rule applied may ultimately shift the burden so as to
cast it on the defendant, it is justly cast upon one who should
bear it, as he wrought the confusion.
Where, on reversal, a decree for appellant would deprive
appellee of the right to ruling on exceptions taken by him to the
master's report which were not passed on by the court, and it
appears that other questions of law were not passed on below, and
also that material evidence was omitted, the case will be remanded
with power to hear and determine on new testimony and for further
proceedings not inconsistent with the opinion.
173 F. 361 reversed.
The current produced by an electric generator is of relatively
low pressure, and for that reason it is impracticable to utilize
it, for power purposes, more than five or
Page 225 U. S. 606
six miles from the central station. It was found, however, that
this pressure, or voltage, could be increased by the use of a
transformer or converter, consisting of a metal core, through and
around which are wound primary insulated wires leading from the
generator. Secondary wires, also insulated, are wound through and
around the same core, and carried thence to the point of
application. The voltage is increased or decreased according as the
secondary wires are wrapped around the core more or less frequently
than the primary wires.
One of the consequences of thus transforming the current is the
generation of heat. In small machines, this is corrected by
radiation, but in large ones, the heat "ages" the iron, lessens the
efficiency of the transformer, and, in time, deteriorates the
insulation around the wires. This latter result causes short
circuits, makes it impracticable to take advantage of the increased
voltage, and thus again restricts the area in which currents of
more than 10 K.W. can be used for producing light and power. 112 F.
418.
Many efforts were made to overcome this difficulty, but without
success until July 12, 1887, when George Westinghouse, Jr., secured
patent 366,362 for an "Electrical Converter" which, his application
stated, was intended to prevent the converter's becoming
"overheated when employed for a long time in transforming currents
of high electromotive force." Extracts from the specification and
claims are copied in the margin.
*
Page 225 U. S. 607
Referring specially to the specifications and Claim 4, which is
here involved, and speaking generally, rather than technically, it
will be seen that the transformer consisted of a core, composed of
groups of thin metal plates, so plugged apart as to leave (a) open
spaces in the core. The primary and secondary wires were wound
through rectangular openings near the ends of these plates. The
entire apparatus was then placed in a case filled with
nonconducting oil, which, when heated, circulated in and around the
transformer, being cooled by contact with the exterior surface of
the enclosing box or receptacle. This invention proved to be of
immense value, and made it possible (112 F. 418, 117 F. 498) to
transmit and apply powerful currents so as to produce power and
light at a great distance from the generating plant. The patent was
utilized by the Union Carbide Company, and on May 10, 1900, the
Westinghouse Electric & Manufacturing Company, as assignee of
George Westinghouse, sued that company for infringing Claim 4. The
transformers which the Carbide Company was using had been sold by
the Wagner Company. As vendor and
Page 225 U. S. 608
warrantor, the latter therefore defended, and admits that the
decree (112 F. 417) of November 11, 1901, sustaining the validity
of Claim 4, is, as to it,
res judicata. That decree was
affirmed May 29, 1902 (117 F. 495), and on June 24, 1902, the
Westinghouse Company brought this suit (129 F. 604) against the
Wagner Company, praying for damages and profits, and also for an
injunction against further infringement.
It appeared that, after the decree in the
Carbide case,
the Wagner Company had instructed its experts to build a
transformer that would not infringe the Westinghouse patent. They
thereupon devised one, referred to herein as Type M, which omitted
the (a) open spaces in the core, but substituted (b) spaces between
the coil, and (c) spaces between the coil and the core.
The court held that these Type M transformers, eliminating
spaces in the core, were not an infringement of Claim 4, and
thereupon refused the injunction. 129 F. 604. But the defendant, in
its answer, admitted that it had infringed Claim 4 by the
manufacture of transformers which, as it subsequently developed,
contained openings (a) in the core, and also (b) openings between
the coils, and (c) between the coil and core. The case was
therefore referred to a master to state an account of damages and
profits arising from the infringement of Claim 4 prior to June 24,
1902.
On the hearing, it appeared that the Wagner Company manufactured
various electrical appliances that had been made in the same shop,
by the same workmen, and under the same general superintendence as
that employed in making the transformers. No account had been kept
which would show the cost of labor and shop expenses attributable
to these transformers. Nor was there anything on the books
indicating what, if any, profit had been realized from their
sales.
The gross receipts of $2,314,744.75 were mingled. The
Page 225 U. S. 609
books only showed a gross profit of about eight percent, but it
appeared that the plant had grown and the business had extended
during the period covered by the accounting. There was testimony
that the company had the general policy of fixing prices at a
figure which would net twenty-five percent. The master made an
elaborate analysis of the data as to flat cost of labor and
material, shop expenses, and commissions applicable to the
transformers. From this data and the policy of the company, he
ultimately reached the conclusion that the company had made a
profit of $132,433 on the $955,271.76 which the books showed had
been received from the sale of several thousand infringing
transformers. But, at the close of the plaintiff's testimony, the
defendant demurred to the evidence on the ground that it failed to
show that any profit had been made in the sale of the infringing
transformers. The demurrer was overruled. The defendant then
claimed that the infringing transformers contained elements of the
patent which were not embraced in Claim 4, for which alone this
suit was proceeding, and that no profit due to those elements could
be recovered in this case unless the plaintiff apportioned the
gains due solely to Claim 4. It also offered evidence, including a
heat test, tending to support its contention that a transformer
containing only the elements covered by Claim 4 was of little
utility; that it operated mainly to reduce the heat in the core,
when it was much more important to keep the coils cool; that the
infringing transformers contained spaces (b) between the coils and
(c) between coil and core which, it contended, were additions and
noninfringing improvements, contributing to the profits, if any had
been made.
In reply and to disprove the defendant's contention, the
plaintiff relied, among other things, on the fact that, upon the
hearing of the application to enjoin the defendant from
manufacturing transformers containing only (b)
Page 225 U. S. 610
spaces between the coil and (c) between coil and core, the
Wagner Company had contended that these grooves or channels had
been used to avoid infringement, although they "crippled the coils"
and actually "lessened the electrical efficiency of the
transformers."
At the conclusion of the lengthy testimony, the substance of
which is barely outlined above, the master found from the evidence
and under the decision in 117 F. 498, binding on defendant, that
Claim 4 was an entirety, covering not only open spaces in the core,
but the use of the oil in a closed receptacle for cooling the
transformer; that all the commercial value of those sold by the
defendant was due to the use of Claim 4 of plaintiff's patent, and
not to additions made by the defendant. He recommended that a
decree should be entered against the defendant for $132,433.35,
"being approximately 25 percent on the net amount of the sales
of infringing transformers after deducting commissions and fixing
the factory cost at 40 percent."
The defendant filed many exceptions, among others:
"That the complainant has not shown what was the profit made by
defendant on its transformers, due to the patented invention of
Claim 4, as distinguished and segregated from the other features
contained in said transformers."
There were also numerous exceptions as to the master's method of
stating the account. These and others were not specifically passed
on, because the circuit court and the circuit court of appeals (one
judge dissenting) held (173 F. 361) that Claim 4 was a limited,
detailed claim; that the additions made by the defendant were
noninfringing and valuable improvements which contributed to the
profits; that the burden of apportionment was upon plaintiff, and,
having failed to separate profits, it was only entitled to a decree
for nominal damages. The court (one judge dissenting) also
affirmed
Page 225 U. S. 611
the decree that Type M was not an infringement of Claim 4.
Page 225 U. S. 613
MR. JUSTICE LAMAR, after making the foregoing statement of the
case, delivered the opinion of the Court.
The statute makes the decision of the circuit court of appeals
final in patent cases, and the plaintiff's petition for the writ of
certiorari herein was not granted for the
Page 225 U. S. 614
purpose of reexamining the court's ruling that defendant's Type
M transformer was not an infringement of Claim 4 of the
Westinghouse patent. The writ was issued in view of the holding
that, though the master found that the defendant had made a profit
of $132,000 from the sale of infringing transformers, the plaintiff
could yet only recover $1, because it failed to separate the
profits made by its patent from those made by the defendant's
addition.
1. The question as to who has the burden of proof in cases like
this is one of great practical importance, and constantly arises in
patent cases. There has been much controversy on the subject, and a
conflict in the decisions. The authorities cited in the briefs of
the two litigants, and others bearing on the subject, have been
examined, but we shall not undertake to separately review them, for
they disagree not so much as to the rule as to its application. It
will be sufficient for the present purposes to say that:
(a) Where the infringer has sold or used a patented article, the
plaintiff is entitled to recover all of the profits.
(b) Where a patent, though using old elements, gives the entire
value to the combination, the plaintiff is entitled to recover all
the profits.
Hurlbut v. Schillinger, 130 U.
S. 472.
(c) Where profits are made by the use of an article patented as
an entirety, the infringer is liable for all the profits "unless he
can show -- and the burden is on him to show -- that a portion of
them is the result of some other thing used by him."
Elizabeth
v. Pavement Co., 97 U. S.
127.
(d) But there are many cases in which the plaintiff's patent is
only a part of the machine and creates only a part of the profits.
His invention may have been used in combination with valuable
improvements made, or other patents appropriated by the infringer,
and each may have
Page 225 U. S. 615
jointly, but unequally, contributed to the profits. In such
case, if plaintiff's patent only created a part of the profits, he
is only entitled to recover that part of the net gains. He must
therefore
"give evidence tending to separate or apportion the defendant's
profits and the patentee's damages between the patented feature and
the unpatented features, and such evidence must be reliable and
tangible, and not conjectural or speculative; or he must show, by
equally reliable and satisfactory evidence, that the profits and
damages are to be calculated on the whole machine, for the reason
that the entire value of the whole machine, as a marketable
article, is properly and legally attributable to the patented
feature."
Garretson v. Clark 111 U. S.
121.
The real controversy arises in applying this principle to those
cases where it is impossible to separate the single profit into its
component parts.
2. In considering the question presented by the record here, it
is to be borne in mind that Congress has legislated (Rev.Stat.
§ 4921) with a view of affording the patentee ample redress
against the infringer. It not only makes the latter liable for
damages -- sometimes three-fold damages -- but for all profits
derived from the use or sale of plaintiff's invention. The rule as
to the burden of proof has, however, been so applied that this
statutory right has been often nullified by those infringers who
had ingenuity enough to smother the patent with improvements
belonging to themselves or to third persons. In such cases, the
greater the wrong, the greater the immunity; the greater the number
of improvements, the greater the difficulty of separating the
profits. And if that difficulty could only be converted into an
impossibility, the defendant retained all of the gains because the
injured patentee could not separate what the guilty infringer had
made impossible of separation.
Manifestly such consequences demonstrate that either
Page 225 U. S. 616
the rule or its application is wrong. The rule is sound, for it
but announces the general proposition that the plaintiff must prove
its case and carry the burden imposed by law upon every person
seeking to recover money or property from another. But the
principle must not be pressed so far as to override others equally
important in the administration of justice. It may serve to
illustrate the rule and its limitations if, at the risk of stating
the obvious, we apply it to the various steps of this case.
The plaintiff proved its patent, and that it had been infringed
by the defendant in the manufacture of several thousand
transformers, which sold for $955,000. The patent was itself
evidence of the utility of Claim 4, and the defendant was estopped
from denying that it was of value.
Lehnbeuter v. Holthaus,
105 U. S. 94. But
no matter how great its presumptive or actual value, it did not
follow that the defendant had made a profit by the sale of the
infringing transformers. And so, having sued for profits, the
Westinghouse Company was under the burden of showing they had been
made. This it did to the satisfaction of the master, who found that
the defendant had netted $132,000 from their sale.
The defendant then had the right either to disprove the
plaintiff's case or to offer evidence in mitigation, or both.
Accordingly, it submitted evidence tending to show that the spaces
added by the defendants were noninfringing and valuable
improvements which had contributed to the making of the profits. In
reply, the Westinghouse Company insisted that Claim 4 was an
entirety, covering a circulatory system in and around a transformer
placed in an oil-filled receptacle; that it embraced the
"intervening spaces in the coil" because at least a part of the
coil was in the core; that, if these spaces were held not to be
infringements, they had in fact, as employed by the defendant,
added nothing to the profits, but, on the contrary, had crippled
the coil and lessened the electrical
Page 225 U. S. 617
efficiency of the transformer. 129 F. 607. For that reason, the
plaintiff contended that it had shown that all the gains were
"legally attributable to the patented feature."
Garretson v.
Clark, 111 U. S. 121;
Elizabeth v. Pavement Co., 97 U.
S. 127 (6);
Crosby Steam Gage & Valve Co. v.
Consolidated Safety Valve Co. 141
U. S. 454;
Keystone Mfg. Co. v. Adams,
151 U. S. 144,
151 U. S. 145.
This view was sustained by the master. But if it be assumed, as was
found to be the fact by the court, that the spaces were
noninfringing and valuable improvements, it may then have
prima
facie appeared that these changes had contributed to the
profits. If so, the burden of apportionment was then logically on
the plaintiff, since it was only entitled to recover such part of
the commingled profits as was attributable to the use of its
invention.
3. Lindley, L.J. said in
Siddell v. Vickers, 9
Rep.Pat.Cas. 162, that there "was no form of account more difficult
to work out that an account of profits." But that is no reason why
the plaintiff should be denied its rights. The problem here, though
different, was in many respects analogous to that presented in
those cases in which it is necessary to separate the interstate
from the intrastate earnings made by a railroad where the same
track, rolling stock, depots, and labor are employed at the same
time in making gross receipts. These commingled expenses must be
apportioned between the two classes of earnings in order to
determine whether the intrastate rate is confiscatory. The courts,
"while recognizing the impossibility of reaching a conclusion that
is mathematically exact," have, in addition to all the other
evidence bearing on the question, received "the testimony of
experts as to the relative costs of doing a local and through
business."
Chicago, M. & St.P. R. Co. v. Tompkins,
176 U. S. 178.
The converse is true. What is permissible in an effort to separate
costs may also be done in a patent case where it is necessary to
separate profits.
Root v.
Lake
Page 225 U. S. 618
Shore & M. S. Railway Co., 105
U. S. 198.
See also Providence Rubber Co. v.
Goodyear, 9 Wall. 802. In effect, this was
attempted in the present case. Witnesses who had been in the
employment of the defendant, and who had kept the books, purchased
the material, superintended the construction, and fixed the price
of the transformers, were not able to show that profits had been
made, and consequently were not able to show what part of the
profits was attributable to the patent and what to the additions,
if found to be noninfringing and valuable improvements.
4. Having, by books and other data, proved to the satisfaction
of the master the existence of profits, the plaintiff had carried
the burden imposed by law, and established every element necessary
to entitle it to a decree, except one. As to that, the act of the
defendant had made it not merely difficult but impossible to carry
the burden of apportionment. But plaintiff offered evidence tending
to establish a legal equivalent. It had proved the existence of a
fact which, whether treated as a rule of evidence or as a matter of
substantive law, would entitle it to a decree for all the profits.
The method was different from that mentioned in the second branch
of the rule in the
Garretson case, 111 U.S.
111 U. S. 121,
but the plaintiff had now presented proof to demonstrate its right
to the whole of the fund because of the fact that the defendant had
inextricably commingled and confused the parts composing it. This
result would not be in conflict with the principle which, in the
first instance, imposed the burden of proof on the plaintiff, but
merely gave legal effect to a new fact which, as a matter of law,
entitled the patentee to a particular judgment. It presented a case
where the court was called on to determine the liability of a
trustee
ex maleficio, who had confused his own gains with
those which belonged to the plaintiff. One party or the other must
suffer. The inseparable profit must be given to the patentee or
infringer.
Page 225 U. S. 619
The loss had to fall on the innocent or the guilty. In such an
alternative, the law places the loss on the wrongdoer.
5. It is said, however, that the rule does not apply to patent
cases. Why it should be limited does not appear. It is admitted
that an injunction may be granted against selling infringing
devices even though the result will be to prevent the defendant
from using valuable appliances confused with the patented device.
And Lord Eldon treated this conceded right to enjoin as an
application of the rule relating to the confusion of goods. He
therefore restrained the publication of a book, a large portion of
which was original, because copyright matter was incorporated
therein, saying in
Mawman v. Tegg, 2 Russ.Ch. 385,
390:
"As to the hard consequences which would follow from granting an
injunction when a very large proportion of the work is
unquestionably original, I can only say that if the parts which
have been copied cannot be separated from those which are original
without destroying the use and value of the original matter, he who
has made an improper use of that which did not belong to him must
suffer the consequence of so doing."
This case was cited and approved in
Callaghan v. Myers,
128 U. S. 658,
where the infringer, who had blended his own with copyright matter
in a volume which sold for a profit, was made to "abide the
consequences on the same principle that he who has wrongfully
produced a confusion of goods must alone suffer." In one of these
cases, the original matter was less, and in the other more, than
that unlawfully appropriated. In both, as in patent cases, the
infringer was a "trustee for the plaintiff in respect of profits."
Root v. Lake Shore & M.S. Railway, 105
U. S. 214. And the liability is not lessened because the
confusion is due to a wrongful appropriation by a trustee
de
son tort, instead of carelessness of a trustee lawfully
appointed. Nor is it limited to those cases where
Page 225 U. S. 620
the patented device is shown to have preponderated in the
creation of the profits. The owner of a small part of the fund is
as much entitled to the protection of the law as the owner of a
larger share. The rule, however, is not intended to penalize the
infringer, nor to give the patentee profits to which he is clearly
not entitled. So that where, by general evidence, expert testimony,
or otherwise, it is shown that his patent is of relatively small
value, it will often be possible to prove that, at the utmost, it
could not have contributed to more than a given amounts of the
profits.
Lupton v. White, 15 Vesey Jr. 432-440. In such
cases, except possibly against one who had concealed or destroyed
evidence or been guilty of gross wrong, the plaintiff's recovery
cannot exceed the amount thus proved, even though it be impossible
otherwise more precisely to apportion the profits.
6. But when a case of confusion does appear -- when it is
impossible to make a mathematical or approximate apportionment --
then, from the very necessity of the case, one party or the other
must secure the entire fund. It must be kept by the infringer or it
must be awarded by law to the patentee. On established principles
of equity and on the plainest principles of justice, the guilty
trustee cannot take advantage of his own wrong. The fact that he
may lose something of his own is a misfortune which he has brought
upon himself, and if, as argued, the fund may have been made by the
use of other patents also, for which he may be liable in another
case, it is again a misfortune which he has brought upon himself
and an instance of a double wrong causing double liability. He
cannot appeal to a court of conscience to cast the loss upon an
innocent patentee, and by judicial decree repeal the provision of
Rev.Stat. § 4921, which declares that, in case of
infringement, the complainant shall be entitled to recover the
"profits to
be accounted for by the defendant."
This conclusion is said to be in conflict with the
Garretson
Page 225 U. S. 621
and other decisions which, it is claimed, justify the conclusion
that the defendant is entitled to retain all of the profits, even
where the patentee is unable to make an apportionment.
Warren
v. Keep, 155 U. S. 265. An
analysis of the facts of those cases will show that they do not
sustain so extreme a doctrine. For they deal with instances where
the plaintiff apparently relied on the theory that the burden was
on the defendant, and for that or other reasons made no attempt
whatever to separate the profits. None of the cases cited discusses
the rights of the patentee who has exhausted all available means of
apportionment, who has resorted to the books and employees of the
defendant, and by them, or expert testimony, proved that it was
impossible to make a separation of the profits. This distinction
between difficulty and impossibility is involved in the ruling by
the Circuit Court of Appeals of the Sixth Circuit in
Brennan
& Co. v. Dowagiac Mfg. Co., 162 F. 476, where the
Garretson case was distinguished, and the court said:
"In the present case, the infringer's conduct has been such as
to preclude the belief that it had derived no advantage from the
use of the plaintiff's invention. . . . In these circumstances,
upon whom is the burden of loss to fall? We think the law answers
this question by declaring that it shall rest upon the wrongdoer,
who has so confused his own with that of another that neither can
be distinguished. It is a bitter response for the court to say to
the innocent party, 'You have failed to make the necessary proof to
enable us to decide how much of these profits are your own,' for
the party knows, and the court must see, that such a requirement is
impossible to be complied with. The proper remedy to be applied in
such cases is that stated by Chancellor Kent in
Hart v. Ten
Eyck, 2 Johns.Ch. 62, 108, where he said:"
"The rule of law and equity is strict and severe on such
occasion. . . . All the inconveniences of the confusion is thrown
upon the
Page 225 U. S. 622
party who produces it, and it is for him to distinguish his own
property or lose it."
It may be argued that, in its last analysis, that is but another
way of saying that the burden of proof is on the defendant. And no
doubt such, in the end, will be the practical result in many cases.
But such burden is not imposed by law, nor is it so shifted until
after the plaintiff has proved the existence of profits
attributable to his invention, and demonstrated that they are
impossible of accurate or approximate apportionment. If then the
burden of separation is cast on the defendant, it is one which
justly should be borne by him, as he wrought the confusion.
7. This conclusion would apparently result in a decree in favor
of the appellant. But such an order, under the peculiar facts of
this case, would operate to deprive the defendant of the right to a
ruling on the exceptions filed to the report. The master held that
the entire commercial value of the transformer was due to the
invention covered by Claim 4, and that therefore all the profits
belonged to the Westinghouse Company. The court, on the other hand,
found that the defendant's additions were not infringements, and
had contributed to the profits, and that, because of the failure to
make a separation, the plaintiff was entitled only to nominal
damages. For this reason, it did not specifically pass on
defendant's exceptions. Other questions of law and fact involved in
the accounting were not considered. Neither the court nor the
master discussed the question of apportionment, and the record does
not afford satisfactory data for entering a final decree. This no
doubt arises from the fact that both parties relied so entirely
upon their theory that the burden was on the other that facts were
not proved which might otherwise have been established. The decree
is therefore reversed, and the case remanded with power to hear and
determine motions to amend the pleadings and with directions that
the case be recommitted to a master for a new hearing on
Page 225 U. S. 623
all the questions involved in the original reference, and, on
evidence already submitted and such additional testimony as may be
offered, for further proceedings not inconsistent with this
opinion.
Reversed.
*
"The core is preferably composed of thin plates of soft iron . .
. separated individually or in pairs from each other by thin sheets
of paper or other insulating material. . . . The plates are
preferably constructed with two rectangular openings through which
the wires pass. . . . Each group of -- say five or six plates -- is
preferably separated from the succeeding group by air spaces. These
may be produced by passing tubes, which may be of soft iron or
other metal, or of vulcanized fiber, along the lengths of the
plates. It may be sufficient in other cases to block the group of
plates apart at intervals instead of extending the tubes the entire
length. Preferably also the primary and secondary coils are
separated from each other in a similar manner."
"Where the converter is to be used in the open air, the tube
will permit a free circulation of air, and thus aid in keeping the
converter cool."
"It may be preferred in some instances to surround the converter
with some oil, or paraffin or other suitable material, which will
assist in preserving insulating and will not be injured by heating.
This material, when in a liquid form, circulates through the tubes
and intervening spaces of the coils and plates, and preserves the
insulation, excludes the moisture, and cools the converter."
"The entire converter may be sealed into an enclosing case . . .
which may or may not contain a nonconducting fluid or gas."
"I claim as my invention . . . 1 . . . ; 2 . . . ; 3. . . ."
"4. The combination, substantially as described, of an electric
converter constructed with open spaces in its core, an enclosing
case, and a nonconducting fluid or gas in said case, adapted to
circulated through said spaces and about the converter."
