¶1The defendant contends that the apparatus offered was inadmissible first, because of the “ insufficiency of *53. . . [the] . . . ex parte experiments intended to show the reliability of the machine,” and second, because of the failure of the Commonwealth “ to show the trustworthiness of said stop watch mechanism, an integral part of the apparatus.” j In support of the first objection he insists that the evidence of the experiments described in the fifth paragraph of the “ agreed statement of facts ” was inadmissible and the experiments themselves insufficient because the conditions under which the experiments were performed differed from those under which the experiment in the case in question was performed, the difference being that in the former the apparatus was used to photograph a stationary-object, while in the latter the object was moving; and also that in the former the apparatus was used only to ascertain distance, while in the latter it was used to ascertain something more, namely, “ speed as shown by both distance and time.”
¶2As a rule the question whether evidence of experiments shall be admitted depends largely upon the discretion of the trial judge; and his action in the exercise of this discretion will not be reversed unless plainly wrong. Field v. Gowdy, 199 Mass. 568, and cases cited. In this case the result of the experiments did not depend upon the fluctuations of human agencies, nor on conditions whose relations to the result were uncertain, but upon the immutable working of natural laws ; and upon the evidence the presiding judge may well have found that such experiments were likely to be more reliable as to the speed of the automobile than the conjectural statement of an eye witness or the interested statement of a chauffeur. We cannot say as matter of law that the evidence would not justify the judge in coming to the conclusion that the experiments would be useful in determining the speed of the car. Indeed it would seem desirable to have some machine whose action being dependent upon the uniform working of the laws of nature would record the speed of a moving object.
¶3Hor is the fact that the experimenter was not an expert fatal to the introduction of the machine. A man may testify to the existence of thunder and lightning and the disastrous results therefrom without being an expert on electricity or electrical phenomenon. For a discussion of the law relating to the admissibility of experiments see among other cases Baker v. Harrington, 196 Mass. 339, and cases cited.
¶4*54The evidence as to the accuracy of the chronometer was admissible and justified the trial judge in submitting that question to a jury. Moreover it was sufficient to warrant a finding by the jury that the chronometer was a correct recorder of time.
¶5It follows that there was no error in admitting the instrument in question, or the evidence as to its construction, or that relating to the experiments.
¶6 Exceptions overruled.