1. The defendant excepts to the admission of evidence that his boiler was not provided with the fusible plug prescribed to be used by the Sts. of 1850, c. 277, and 1852, c. 247, and the instructions of the court as to the use of such evidence, when admitted. The obvious, and we think conclusive, answer to this exception is, that the evidence was admitted without objection and without any qualification or limitation, and when thus admitted it was competent evidence upon the question of-the defendant’s liability, arising under the statute or at common law. The evidence being thus admitted, if the objection had been taken that the declaration was imperfect, an amendment would have been allowed, almost as a matter of course. But the objection was not taken, the exception was not made, and the point is not open.
2. The defendant sought to break the force of the testimony, and offered to show that it was not the custom among persons, using such boilers as his, to have and use such fusible plugs. The court rightly held that a custom not to observe the law could not be shown.
3. The exception to the instructions of the presiding judge as to what was meant by ordinary care cannot be sustained. The instructions were good sense and good law, well expressed. What is ordinary care cannot be determined abstractly. It has relation to and must be measured by the work or thing done and the instrumentalities used, and their capacity for evil as well as good. What would be ordinary care in one case may be gross negligence in another. We look to the work, its difficulties, dangers and responsibilities, and then say, What would and should a reasonable and prudent man do in such an exigency ? The word “ ordinary ” has a popular sense, which would greatly relax the rigor of the rule. The law means by “ ordinary care ” the care reasonable and prudent men use under like circumstances.
4. The next ground of exception, upon which the defendant relies, is the refusal of the presiding judge to instruct the jury that if the accident would not have happened without negligence on the part of the engineer, the defendant was not liable. We think such instruction cnuld not have been given. The do* *281fault of the defendant might have been, not only in having a boiler imperfectly constructed and guarded, but an incompetent and habitually careless and negligent engineer. It is now well settled law, that one entering into the service of another takes upon himself the ordinary risks of the employment in which he engages, including the negligent acts of his fellow workmen in the course of the employment. Farwell v. Boston & Worcester Railroad, 4 Met. 49. King v. Boston & Worcester Railroad, 9 Cush. 112. Gillshannon v. Stony Brook Railroad, 10 Cush. 228. It has not been settled that the master is not liable for an injury which results from the employment of an incompetent servant or use of a defective instrument. If the defendant employed a competent engineer, and used a boiler properly constructed and guarded, he would not be liable for injuries resulting from an act of carelessness or negligence of such engineer. But we are not prepared to say that if one uses a dangerous instrumentality without the safeguards which science and experience suggest or the positive rules of law require, he is not to be responsible for an injury resulting from such use, because the negligence of one of his servants may have contributed to the result, or because a possible vigilance of the servant might have prevented the injury. The very object and purpose of a safeguard like the fusible plug are protection against the occasional carelessness and negligence of the engineer. It is intended to be in some degree a substitute for his vigilance — to keep watch -if he nods. To say that the master should not be responsible for an injury which would not have happened had a safeguard required by law been used, because the engineer was negligent, would be to say, in substance and effect, that he should not be liable at all for an injury resulting'from the failure to use it.
The case of Hayes v. Western Railroad, 3 Cush. 270, relied upon by the defendant, proceeds upon the ground that the injury was caused by the negligence of the workman, his failure to be in his place and discharge his duty, and that the train being short of hands was wholly immaterial. Otherwise, it would be difficult to sustain it. See language of the court, p. 274.
The instructions of the presiding judge upon the liability of *282the master, as affected by the relation of the defendant as fellow servant of the engineer, are not in our judgment liable to just exception. The counsel for the defendant asks of us a liberal application of the principle by which the servant is presumed to assume the risks of the business, and among others the negligence of his fellow servants, for the protection of the master. The principle should not be so extended as to impair in the least degree the obligation resting upon the master, in the prosecution of a business involving unusual risk of health or life or limb, to employ well guarded instruments and competent agents.
Exceptions overruled *
See Bartonshill Coal Co. v. Reid, 3 Macqueen, 266; Bartonshill Coal Co. v. McGuire, 3 Macqueen, 300; Holmes v. Clarke, 6 H. & N. 349; Searle v Lindsay, 11 C. B. N. S. 429; Seaver v. Boston & Maine Railroad, 14 Gray, 466; Ryan v. Fowler, 24 N. Y. 410; Buzzell v. Laconia Manuf. Co. 48 Maine, 113