TRESPASS AND INSURANCE 1159 



there are collars or shoulders. Also occasionally there are more prominent projections 

 on the tubing string known as tubing catchers. 



In some wells the distance to the tubing catcher is known, and it was observed that 

 the distance to the fluid surface could be measured by a simple time-distance proportion 

 formula. (See page 1129.) 



There were wells, however, in which the distance from the tubing catcher was 

 unknown. To provide for this, Walker utilized the fact that the sections of tubing 

 used in a given oil well are generally of equal length and consequently the shoulder 

 joints ordinarily are at equal intervals from each other. The section lengths may vary 

 in different wells. Walker's immediate objective was to measure the unknown distance 

 to the tubing catcher, from which the depth to the fluid surface could be readily ascer- 

 tained by the formula referred to above. Walker thereupon concluded to measure the 

 unknown distance to the tubing catcher by observing and recording the shoulder echo 

 waves. Multiplication of the number of shoulders as revealed by the number of echo 

 waves times the length of an average pipe section would show the distance to the 

 tubing catcher. 



The Lehr and Wyatt instrument was capable of recording the tubing collar echoes 

 but was not efficient, and Walker therefore added to the Lehr and Wyatt apparatus 

 a mechanical acoustical resonator which would make the shoulder echo waves more 

 prominent on the graph and easier to count. 



The mechanical acoustical resonator was not per se new with Walker, but was an 

 already well-known device. It consisted primarily of a short pipe which would receive 

 the wave impulses from the casing head. This pipe, being one-third the length of the 

 tubing joints, would act as a tuner adjusted to the third harmonic of the frequency of 

 the shoulder echo waves, amplifying these waves and thereby minimizing the random 

 echoes. Walker attached to the resonator a mechanical adjusting means so that the 

 length of the resonator tube could be set exactly at one-third of the interval between 

 shoulders in any particular well. 



The Halliburton Oil Well Cementing Company began the use of an electrical filter 

 apparatus which achieved results similar to Walker's mechanical device, and Walker 

 brought suit against Halliburton in the Federal Court at Los Angeles for infringement 

 of patent No. 2,156,591 and two other patents, the latter never reaching the Supreme 

 Court. The District Judge held the Walker patent as to claims 1, 13, 14, 15 and 17 

 (the only ones in issue) valid and infringed. Halliburton appealed to the Ninth Circuit 

 Court of Appeals. The Court of Appeals affirmed the District Court with respect to 

 the patent under discussion, concluding that Halliburton's electrical filter was equiva- 

 lent, under the patent law, to Walker's mechanical resonator. The court commented 

 that while Halliburton's device was by no means a Chinese copy of Walker's, the court 

 considered that the Walker patent was entitled to a liberal construction and to a fair 

 range of equivalents. 



As mentioned before, carrying a patent case from the Court of Appeals to the 

 Supreme Court is not a matter of right in the absence of conflicting decisions, and 

 there were none. Halliburton's counsel therefore filed a petition for ivrit of certiorari 

 in the Supreme Court, asking for a special ruling by sufficient members of the court 

 to call up the case for consideration on its merits. In the first instance the petition was 

 denied, but a week later the Supreme Court accepted the case. It was briefed and 

 argued before a court composed of an even number of judges. They were equally 

 divided in their opinion and under such circumstances the decision by the Court of 

 Appeals was necessarily affirmed. A petition for a re-hearing in the Supreme Court 

 was filed and, this being finally granted, the case was ordered re-argued. 



The final opinion of the Supreme Court was delivered by Mr. Justice Black with 

 a dissent by Mr. Justice Burton. The opinion reviewed most of the facts referred to 

 above and then addressed attention to the claims, their technical construction as patent 

 claims, and whether these claims fulfilled the requirements of the patent law. 



Revised Statute 4888, 35 U.S.C. Section 33, is important in this regard and neces- 

 sary to an understanding of the case. It is therefore quoted here : 



