This action of tort was brought under the Federal employers’ liability act, 45 U. S. C. (1952) § 51 et seq. (hereinafter called the act). The plaintiff’s bill of exceptions presents the question whether the trial judge correctly directed a verdict for the defendant.
The case was referred to an auditor whose report, together with certain documentary evidence, was introduced in evidence at the jury trial. The facts, in their aspect most favorable to the plaintiff, are stated below.
The plaintiff was a track worker, subject to the act, employed by the defendant. On September 12, 1952, he was *180put in charge of three men and told to move some rails within the defendant’s yards. Each rail weighed between six hundred and eight hundred pounds, and was carried by means of two pairs of tongs. One pair was used to lift each end of a rail and the plaintiff and each of the other three men in the group held one handle of a pair of tongs.
The four men moved several rails with difficulty. Before moving another rail, the plaintiff “instructed his coworkers on the other end of the rail not to drop their end until he gave them a signal to do so.” While carrying this rail, “suddenly without warning the two men on the other end of the rail dropped their end .... To avoid being struck by the rail, the plaintiff jumped and as he did his left foot ... went into a hole . . . [about six inches deep and twelve inches square] recently . . . dug . . . causing the plaintiff severe injury.”
The plaintiff received hospital treatment and thereafter remained under regular treatment by a physician in the employ of the defendant. In June, 1954, he was again admitted to the hospital. “The diagnosis of a ruptured disc was arrived at and on July 27, 1954,” he underwent an operation. His aggregate hospital and medical bills amounted to $1,420.60.
From October 9, 1952, to March 20, 1953, the defendant made a number of payments to the plaintiff amounting in the aggregate to $2,400. On March 20, 1953, the “plaintiff signed a general release prepared by the defendant releasing the defendant ‘ on account of damages of whatever ... description now existing or which may arise . . . out of the injuries . . . received by me at . . . Worcester . . . on . . . 12th . . . September, 1952.’ . . . [T]he plaintiff also wrote on the release . . . ‘ I have read this release and understand it.'"
Despite the release, the auditor found for the plaintiff and assessed damages in the sum of $12,400 from which the sum of $2,400 already paid was to be deducted. Further findings of the auditor about the release are discussed below in connection with the consideration of its validity.
*181The defendant at the trial before a jury introduced in evidence the release itself and an instrument, dated March 20, 1953, purporting to be signed by the plaintiff, reading, “I have this day executed a general release for $2400.00 on account of injuries sustained by me on September 12, 1952. I agree that none of the amount received is payment for time lost, and that I have no right or claim to any payment for time lost.” There was also in evidence a letter, dated March 2, 1953, from the plaintiff reading in part, “1 am writing you on [sic] regards to a settlement that you and I were talking about the last time that you were here. I am ready to make a settlement for four months pay and I will not return to the Railroad .... If this agreement is agreeable with you drop me a line and I will sign all papers that will have to be taken care of.”
1. Federal law, and not the law of Massachusetts, applies to the issue under the act whether the evidence warrants a finding that the defendant was negligent. Labonte v. New York, N. H. & H. R.R. 333 Mass. 420, 421-422, cert. den. 351 U. S. 974. Ellis v. Union Pac. R.R. 329 U. S. 649, 653. Rogers v. Missouri Pac. R.R. 352 U. S. 500, 507, note 13. Federal law also controls the determination whether the release of liability under the act is valid. Dice v. Akron, C. & Y. R.R. 342 U. S. 359, 361-364. See South Buffalo Ry. v. Ahern, 344 U. S. 367, 372. See also McCarthy v. New York, N. H. & H. R.R. 285 Mass. 211, 215.
2. The subsidiary findings of the auditor would warrant a jury in finding that the defendant was chargeable with negligence under the act. “Under this statute the test of a jury case is simply whether the proofs justify with reason the conclusion that employer negligence played any part, even the slightest, in producing the injury or death for which damages are sought. . . . The statute expressly imposes liability upon the employer to pay damages for injury or death due 'in whole or in part’ to its negligence”. Rogers v. Missouri Pac. R.R. 352 U. S. 500, 506-507. 45 U. S. C. (1952) § 51. The act expressly makes the employer liable, to persons entitled to benefits of the act, for the negligent *182acts of fellow employees (Hietala v. Boston & Albany R.R. 295 Mass. 186, 187-188, cert. den. sub nom. Boston & Albany R.R. v. Hietala, 299 U. S. 589). Recent decisions of a majority of the Supreme Court have held that, under this act, very slight evidence, from which negligence might conceivably be inferred, requires the submission of the case to a jury. Webb v. Illinois Cent. R.R. 352 U. S. 512. Herdman v. Pennsylvania R.R. 352 U. S. 518. Moore v. Terminal R. R. Assn. of St. Louis, 358 U. S. 31, 34. See Rogers v. Missouri Pac. R.R., supra, at pp. 503-504; McBride v. Toledo Terminal R.R. 354 U. S. 517; Ringhiser v. Chesapeake & O. Ry. 354 U. S. 901. See also Arnold v. Panhandle & S. F. Ry. 353 U. S. 360; and cases collected in Sinkler v. Missouri Pac. R.R. 356 U. S. 326, 332-333, note 1.
The presence of a newly dug hole (six inches deep and twelve inches square) in a railroad yard, where minor changes in conditions and slight irregularities in ground surface might well be expected, by itself hardly seems sufficient basis for a finding that the railroad provided the plaintiff with an unsafe place to work. Labonte v. New York, N. H. & H. R.R. 333 Mass. 420, 424, cert. den. 351 U. S. 974. The jury, however, would have been warranted in finding that the sudden dropping, without warning and despite the plaintiff’s instructions to his coworkers, of one end of the rail was negligent conduct for which the defendant was responsible under the act. See McCurry v. Thompson, 352 Mo. 1199, 1204-1206; Cules v. Northern Pac. Ry. 105 Wash. 281, 285. See also New York Cent. R.R. v. Marcone, 281 U. S. 345, 349-350. Tins conduct could be found to have caused the plaintiff to jump to avoid being hit, without opportunity to select his landing place carefully. See Kane v. Worcester Consol. St. Ry. 182 Mass. 201, 202; Rollins v. Boston & Maine R.R. 321 Mass. 586, 589; Holmes v. New York Cent. R.R. 330 Mass. 155, 160; Chicago Great West. Ry. v. Scovel, 232 F. 2d 952, 957 (8th Cir.), cert. den. 352 U. S. 835; Prosser, Torts (2d ed.) 137-138; Harper and James, Torts, § 16.11. See also Rogers v. Missouri Pac. R.R. 352 U. S. 500, 502-504.
*1833. The defendant pleads in its answer that the plaintiff is barred from recovery by his general release dated March 20, 1953, which the auditor found that the plaintiff signed. This finding was not contradicted by other evidence. The plaintiff contends, however, that there was evidence upon the basis of which (under the Federal decisions) the jury would have been warranted in finding that the circumstances were such as to enable the plaintiff to avoid the release. See Shaw v. Victoria Coach Line, Inc. 314 Mass. 262, 264.
The pertinent findings of the auditor with respect to the release were as follows: (1) Weekly payments of $100 each were made to the plaintiff, over a period of twelve weeks. A $300 payment was made on March 1, 1953. The claim adjuster ‘ ‘ told the plaintiff that he was paying him the wages which he would have earned if . . . employed ” and the plaintiff believed this. (2) The claim agent “represented” that a payment of $900 to the plaintiff, made on March 20, 1953, when the general release was signed, “was likewise for additional wages.” The plaintiff was “not aware that he was signing a release of all claims.” (3) “At the time that the plaintiff signed this release, he believed that it was for back wages due to him.” (4) The plaintiff then “was not aware of the extent or nature of his injuries . . . nor did the defendant’s physician who attended him at that time tell him to what extent . . . the plaintiff was injured.” (5) "On the day that the plaintiff signed the release he did not read” it and he “was under the influence of intoxicating liquor.” ‘(6) The plaintiff underwent substantial medical treatment after March 20, 1953, for spinal injuries, the true nature of which appears to have been diagnosed in June or July, 1954. The auditor found that, in addition to the aggregate of $2,400, in fact paid, the plaintiff should receive $10,000. As the validity of the release must be determined under Federal law, we do not consider, and express no opinion, whether the release could have been disregarded under our Massachusetts decisions.1
*184The Supreme Court has stated that, even under § 5 of the act (45 U. S. C. [1952] § 55), "the releases of railroad employees stand on the same basis as the releases of others. One who attacks a settlement must bear the burden of showing that the contract he has made is tainted with invalidity, either by fraud practiced upon him or by a mutual mistake under which both parties acted.” Callen v. Pennsylvania R.R. 332 U. S. 625, 630. In Dice v. Akron, C. & Y. R.R. 342 U. S. 359, 362, it was said that “a release of rights under the Act is void when the employee is induced to sign it by the deliberately false and material statements of the railroad’s authorized representatives made to deceive the employee as to the contents of the release.” See South Buffalo Ry. v. Ahern, 344 U. S. 367, 372-373.
The decisions of certain of the Federal courts of appeals apply much less definite standards for determining whether releases may be avoided for fraud than are expressed in the Supreme Court’s opinions in the Callen case and the Dice case. See Graham v. Atchison, T. & S. F. Ry. 176 F. 2d 819, 826 (9th Cir.), where the court suggests that even “an innocent misrepresentation” would be "ground for voiding a release induced by it”; Purvis v. Pennsylvania R.R. 198 F. 2d 631, 633 (3d Cir.); Camerlin v. New York Cent. R.R. 199 F. 2d 698, 701-702, 703-704 (1st Cir.); Marshall v. New York Cent. R.R. 218 F. 2d 900, 905-906 (7th Cir.). See also cases, where there was apparently evidence of affirmative misrepresentations by the defendant, like Brown v. Pennsylvania R.R. 158 F. 2d 795, 796 (2d Cir.), and the somewhat analogous decisions like Irish v. Central Vt. Ry. 164 F. 2d 837, 839-840 (2d Cir.), and Gifford v. Wichita Falls & S. Ry. 211 F. 2d 494, 496-497 (5th Cir.). The cases just cited, because of the vagueness of the standard which they state, *185provide an unsatisfactory guide for action with respect to avoiding releases for fraud. Accordingly, we propose to adhere to the plain language of the standards already quoted from the Supreme Court’s decisions in the Callen case (332 U. S. 625, 630) and the Dice case (342 U. S. 359, 362) until and unless, by authoritative rulings of the Supreme Court, those standards are altered.
The auditor’s findings comprise the principal evidence placed before the jury. Because of the introduction at the jury trial of certain correspondence, releases, and other documentary material, the findings on the issue of fraud are deprived of the “compelling” effect which they might otherwise have under the principles stated in Cook v. Farm Serv. Stores, Inc. 301 Mass. 564, 566-567. See Ball v. Williamson, 336 Mass. 547, 551; Institute for Maintaining Drycleaning Standards Model Plant, Inc. v. Wm. Filene’s Sons Co. 336 Mass. 573, 574; G. L. c. 221, § 56; Rule 88 of the Superior Court (1954). Compare Salter v. Leventhal, 337 Mass. 679, 696-697.
Examination of the findings reveals that, on the issue of fraud, they are incomplete and indefinite in respects in which positive and clear findings should have been made one way or another. There was no explicit finding whether the claim agent misrepresented that the general release was only a receipt for wages. The auditor did find that the claim agent represented that the several payments were for wages, but the significance of this is uncertain in view of the plaintiff’s letter of March 2,1953. That letter gives at least strong basis for an inference that, several days prior to the signing of the release, the parties had been discussing settlement in terms of a payment equivalent to a certain number of months’ wages. A jury could not reasonably infer, upon the basis of (a) the statement that the payments were for wages, and (b) the finding that the plaintiff “believed” that the release “was for back wages,” that the claim agent made any separate affirmative representation about the contents of the release. If the auditor concluded that any such representation had been made, he should have said so clearly. *186The auditor also makes no express findings that the claim agent intended to deceive the plaintiff by his statement that the payments were for wages, or that he knew or should have known that the plaintiff was intoxicated, or that he knew or had reasonable cause to believe that his statement, even if innocent, would be interpreted as meaning that the release also dealt only with wages. There is no finding about the extent to which the plaintiff was “under the influence of intoxicating liquor.”
The fact, if found, that the plaintiff was drunk or seriously intoxicated would be, like impairment of mental faculties, “a factor . . . to be considered in determining whether he has been imposed upon by the fraudulent representations of another.” See Shaw v. Victoria Coach Line, Inc. 314 Mass. 262, 266-269; Bowman v. Illinois Cent. R.R. 11 Ill. 2d 186, 202-203, 205-211. So, under the Federal cases, would be the finding that the plaintiff did not read the release (if that finding be believed despite the plaintiff’s written statements to the contrary). See Marshall v. New York Cent. R.R. 218 F. 2d 900, 903-904 (7th Cir.); Humphrey v. Erie R.R. 116 F. Supp. 660, 661, 663 (S. D. N. Y.). See also Graham v. Atchison, T. & S. F. Ry. 176 F. 2d 819, 826 (9th Cir.). Neither of these circumstances, however, even if accepted as true, would seem, standing alone, to be sufficient proof of fraud or ground for avoidance of the release. See Shaw v. Victoria Coach Line, Inc., supra, at pp. 266-267.
Fraud, of course, is not to be presumed. See Stow v. Commissioner of Corps. & Taxn. 336 Mass. 337, 341. In the light of this principle, it would be hard to view as warranted a finding that the release was procured by “deliberately false and material statements . . . made to deceive” (see Dice case, 342 U. S. 359, 362) without an unduly elastic construction of the auditor’s equivocal findings and without permitting unreasonable inferences from those findings. Accordingly,' we rest upon another ground our decision that it was incorrect to direct a verdict for the defendant.
The record does contain findings which might give rise, *187under the Federal cases discussing the act (cf. however, Tewksbury v. Fellsway Laundry, Inc. 319 Mass. 386, 388, infra), to an inference that there was a mutual mistake of fact about the extent of the plaintiff’s injuries when the release was signed on March 20, 1953. The plaintiff was then under the care of “the defendant’s physician” (see Humphrey v. Erie R.R. 116 F. Supp. 660, 663 [S. D. N. Y.]) who did not “tell him to what extent” he was injured. See Graham v. Atchison, T. & S. F. Ry. 176 F. 2d 819, 825 (9th Cir.). Serious injuries were discovered thereafter which were apparently regarded as related to the accident. The settlement made could be found to have been small in relation to the seriousness of the injury as it finally developed. See Bowman v. Illinois Cent. R.R. 11 Ill. 2d 186, 210.
In Callen v. Pennsylvania R.R. 332 U. S. 625, 627-629, the issue whether a release was executed in mutual ignorance of the permanency of an injury was held to be for the jury and it was assumed that, in circumstances similar to those here present, there might be found to be a mutual mistake. Other Federal cases recognize that a mutual mistake about the extent of injuries is ground for avoiding a release under the act. Graham v. Atchison, T. & S. F. Ry. 176 F. 2d 819, 821-825 (9th Cir.); Chicago & N. W. Ry. v. Curl, 178 F. 2d 497, 501-502 (8th Cir.); Humphrey v. Erie R.R. 116 F. Supp. 660, 665-666 (S. D. N. Y.); Cleghorn v. Terminal R.R. Assn. of St. Louis, 289 S. W. 2d 13, 21-22 (Supr. Ct. Mo. 1956). Cf. the different rule in Massachusetts found in Tewksbury v. Fellsway Laundry, Inc. 319 Mass. 386, 388, where Dolan, J., speaking for the court said, “It is settled in this Commonwealth that one who executes a release for consideration for the injuries then known cannot, on the subsequent discovery of injuries not known or suspected at the time of settlement, obtain a cancellation of the release on the ground of mutual mistake, and that the release is binding in the absence of fraud or concealment.” The Federal decisions, of course, are applicable here.
The auditor’s subsidiary findings affecting the issue of mistake are general and provide only slight basis for concluding *188that there was in fact any mutual mistake, but we cannot say that a jury could not infer (a) that the defendant and the plaintiff did not know on March 20 the true extent of the injuries, (b) that the plaintiff and the defendant regarded the injuries as less serious than they turned out to be, and (c) that the parties made their settlement based upon a misapprehension of the extent of the injuries. The auditor might well have made subsidiary findings on these matters, but we think that these inferences were permissible on the findings in fact made by him. Although the plaintiff in his brief made no more than passing reference to the facts which might show mutual mistake, this ground for avoidance of the release was open on the auditor’s findings and under the Federal cases relating to mutual mistake. Accordingly, in the opinion of a majority of the court, it was error to direct a verdict for the defendant.
4. We have noted above various respects in which the auditor’s report should have been more specific and informative. The purpose of such a report is to clarify difficult issues for the jury. The present case is clearly an instance in which recommittal of the report to the auditor for clarification and amplification of the findings would be within the discretion of a judge of the Superior Court, before submitting the case to another jury. See W. R. Grace & Co. v. National Wholesale Grocery Co. Inc. 251 Mass. 251, 253; J. W. Grady Co. v. Herrick, 288 Mass. 304, 310; Staples Coal Co. v. Ucello, 333 Mass. 464, 467. See also Lombardi v. Bailey, 336 Mass. 587, 595-596.
Exceptions sustained.
See eases collected in Tupper v. Hancock, 319 Mass. 105, 107-108, and Century Plastic Corp. v. Tupper Corp. 333 Mass. 531, 533-535; Abrain v. *184Pereira, 336 Mass. 460, 462. See also Griffin v. New York, N. H. & H. R.R. 279 Mass. 511, 515; Barletta v. New York, N. H. & H. R.R. 297 Mass. 275, 278. For cases dealing with avoidance of a release, where affirmative misrepresentations were involved, see Bliss v. New York Cent. & H. R. R.R. 160 Mass. 447, 448, 454; Shaw v. Victoria Coach Line, Inc. 314 Mass. 262, 267; King v. Motor Mart Garage Co. 336 Mass. 422, 426. See as to mutual mistake Tewksbury v. Fellsway Laundry, Inc. 319 Mass. 386, 388.