The bill of exceptions presents two questions: Was the testimony of Stromberg properly admitted? and: Was there evidence of negligence sufficient to entitle the plaintiff to go to the jury?
The exception to the admission of the evidence must be overruled. Stromberg was asked whether, from an inspection of the valve whose breaking caused the injury, he was able to state what would have been an adequate cause for breaking out the piece then missing. This was a proper subject for expert testimony. The witness was a machinist and steam engineer who, for the eighteen years preceding, had worked repairing marine engines and boilers and building boilers and who for nine years before that had been at sea as an engineer. He had never known a valve exactly like the one before him to break, but had known of the breaking of a similar valve. He knew something of castings and of cast iron, but never had made a study of them and did not know all about what defects came in castings and why. Obviously he was qualified to answer the question put to him. His experience enabled him to give evidence of value; even if it was not so universally comprehensive that it covered all possible matters involved in the breaking of a valve. No objection was made to further questions. If the defendant was dissatisfied with his qualification to answer them, it should have objected and obtained rulings on the sufficiency of his expert knowledge in regard to the matters then inquired about. As was said, with abundant citation *393of authority, in Johnson v. Lowell, 240 Mass. 546, 549: “It is settled that whether a witness offered as an expert is qualified to give an opinion, rests very largely in the discretion of the presiding judge whose decision will not be reversed unless clearly erroneous as matter of law.” No clear error of law appears.
The evidence, taken most strongly for the plaintiff, shows that the valve broke in the castiron casting, and that no one could be certain just what caused the break. The valve was of standard make, and had been in use since 1908, under a usual pressure while the vessel was at sea of 180 pounds per square inch. It had been closed for the two days before the accident and was under a pressure of about 120 pounds, which was the pressure at the time it gave way. There was no evidence of the lifetime of such a valve. It had been inspected yearly, the last inspection in the July preceding the December of the accident, and when inspected had been found in good condition. There was no evidence of any old crack. It was necessary to take the valve apart in order to inspect the region of the break. There was no evidence to show that it was usual to take such valves down oftener than once a year. There was no evidence that it had leaked or shown any defect in service. The opinion of Stromberg was the only testimony that the break might have resulted from a hammering caused by condensation in the steam pipe which brought a sudden and unusual strain upon the casting at a time when it was under an undue strain due to being screwed down improperly in closing it. Equally probable explanations were shown. There was no evidence that, in fact, the valve had been screwed down too tightly. We disregard the evidence that the spindle would have broken or stripped or the disk would have given way before the casting would yield had too great pressure been used in screwing down the valve; because, theoretically, the jury might have disbelieved it.
We think the evidence leaves wholly to speculation or conjecture whether the defendant was negligent. It does not present facts which show negligence. It is fully as consistent with the absence as with the presence of careless*394ness. In such a case it is the court’s duty to direct a verdict for the defendant. Doyle v. Boston & Albany Railroad, 145 Mass. 386. In Griffin v. Boston & Albany Railroad, 148 Mass. 143, Mooney v. Connecticut River Lumber Co. 154 Mass. 407, Lowner v. New York, New Haven & Hartford Railroad, 175 Mass. 166, Melvin v. Pennsylvania Steel Co. 180 Mass. 196, and Heuser v. Tileston & Hollingsworth Co. 230 Mass. 299, there were facts furnishing far more basis for trustworthy inference than are presented here. Beattie v. Boston Elevated Railway, 201 Mass. 3, perhaps comes as near this case on its facts as any other, but in that case there was testimony that only through defects in the condition of the electric mechanism and equipment of the car (matters which could have been observed readily on inspection) could the explosion have occurred.
The case falls within the line of decision illustrated by Clare v. New York & New England Railroad, 167 Mass. 39, Wadsworth v. Boston Elevated Railway, 182 Mass. 572, Sheehan v. Goodrich, 207 Mass. 99, Ridge v. Boston Elevated Railway, 213 Mass. 460, Kusick v. Thorndike & Hix, Inc. 224 Mass. 413, Hanna v. Shaw, 244 Mass. 57, and within the principle stated by Sheldon, J. in Carney v. Boston Elevated Railway, 212 Mass. 179,180: “Where as here the cause of the accident has come from the lawful operation by lawful means of an authorized instrumentality, and where any damage or injury that has resulted may have come without any negligence of the defendant, but may have arisen merely as an unavoidable accident from the careful and skilful exercise of its lawful rights in spite of the observance of all proper precautions, there no liability can arise without some affirmative evidence of negligence.”
The defendant’s motion for a directed verdict should have been allowed. We need not consider the exceptions , to the refusal of its requests for rulings.
The exception to the admission of evidence is overruled. The exception to the refusal to direct a verdict for the defendant is sustained.
So ordered.