So far as concerned the possible liability of the City, he left to the jury only the question whether the city employees had been lacking in due care and diligence in their failure to act promptly and effectively once it had been reported to the City that an unusual flow of city water was occurring near where the break in the city water main was later discovered, this of course having nothing to do with what might have caused the break in the water main. Cf. Vaillancourt v. Manchester Gas Co., 1936, 88 N.H. 95, 184 A. 353. Hence, it was the view of the district judge that the agreement of indemnity to be implied from the terms of § 18 of Ch. 27 could not, as a matter of interpretation, be considered as being intended to save the City harmless from the consequences of its own subsequent independent negligence. In this connection it seems to us that there is relevant language of the Supreme Judicial Court in Laskowski v. Manning, 1950, 325 Mass. 393, 398, 91 N.E.2d 231, 234, to the effect that a contract of indemnity "'will not be considered as indemnifying one against his own negligence, or that of his employees, unless its express language requires it.
Furthermore the duty to anticipate injury and take protective action is measured in part by the seriousness of the danger. Vaillancourt v. Manchester Gas Co., 88 N.H. 95, 184 A. 353 (1936). Thus where the burden of precaution to be taken by the defendant is slight compared with the gravity of the harm sought to be avoided, it is unquestionable that the defendant has a duty to take effective precautions to prevent forseeable injury.
The jury were warranted in finding that the defendant should reasonably have anticipated that a break might occur; that it negligently failed to prevent it; and that the defendant did not exercise reasonable care in the maintenance and supervision of its gas main used by it to convey a substance of a dangerous nature having a tendency to escape, which, if not kept confined to the main, might result in serious harm to another. Lewis v. Boston Gas Light Co. 174 Mass. 411. Greaney v. Holyoke Water Power Co. 174 Mass. 437. Thompson v. Cambridge Gas Light Co. 201 Mass. 77. Nugent v. Boston Consolidated Gas Co. 238 Mass. 221, 232. Salem v. Salem Gas Light Co. 241 Mass. 438, 442. Bernier v. Pittsfield Coal Gas Co. 257 Mass. 188, 190. Barbeau v. Buzzards Bay Gas Co. 308 Mass. 245, 247. Harvard Furniture Co. Inc. v. Cambridge, 320 Mass. 227, 229. Dow v. Winnipesaukee Gas Electric Co. 69 N.H. 312, 315. Vaillancourt v. Manchester Gas Co. 88 N.H. 95. There was no error in the denial of the motions for directed verdicts.
National Sheet metal, etc., Co. v. N Y Tel. Co., 5 N.J. Misc. 503, 506, 137 A. 409 ( Sup. Ct. 1927); Vaillancourtv. Manchester Gas Co., 88 N.H. 95, 184 A. 353 ( Sup. Ct. 1936). Plaintiffs urge that a prima facie case of negligence is established by proof not only that there was a gas explosion but that there was a break or leak in the pipe; they say that the existence of the leak is "some evidence of negligence."