GOODE, J.
(after stating the facts.)
1. In support of the point that a verdict should have been directed in defendant’s favor, its counsel advances these propositions : First. There was no evidence tending to show plaintiff’s injuries were due to any of the acts of negligence charged in the petition. Second. The court having required the jury . to find the iron was dumped on plaintiff by reason of one of the castors having sunk into a knot hole, it must be taken for granted that this was the ground of the verdict. But such a finding was a mere conjecture or surmise, unsurported by any evidence to' show that, in truth, a castor ran into the hole. Third. The plaintiff had assumed the risk of the injury. ,
As to the last proposition, we remark that if the negligence of the defendant caused the accident, then the plaintiff did not assume the risk, according to the current decisions of the Supreme Court. [Blundell v. *493Mfg. Co., 189 Mo. 552, 88 S. W. 103; Dakan v. Mercantile Co., 94 S. W. 944.]
We find no evidence to show the truck was badly constructed in itself and for use on a smooth floor. There may have been negligence in loading too many sheets of iron on it, and it looks a great deal like overloading had much to do with the accident. Negligence in that regard was not charged, nor is there such conclusive proof that the accident was due to such negligence as would justify us in denying a recovery on the negligence actually charged. Now assuming that the floor was rough, with many holes in it, as the evidence tends to prove, the question in this connection is, could the jury reasonably infer from the evidence that the machine, constructed as it was and with the floor in that condition, constituted a failure on the part of the defendant to furnish plaintiff a reasonably safe appliance to use and a reasonably safe place to work? As said, the truck itself might have been safe enough on a smooth floor, and the floor might have been safe enough with a truck half as high as this one and of the same dimensions, or the same height and twice the length and breadth. But the truck plaintiff was using was intended to be rolled over a floor with holes in it wherein the castors were liable to catch; and, considering its heighth and the size of the truck’s base in proportion to the size of the top, we think the inference was fair that it was topheavy, unstable and likely to topple the iron off if a jostle occurred' by a castor sinking into a hole in the floor, and thereby injure the employees who were using it. The danger, too■, was not remote and unlikely to be realized until an accident happened. It could be foreseen and prevented. [Anderson v. Box Co., 103 Mo. App. 382, 77 S. W. 486.] In other words, the machine and the floor might well be found not to constitute performance by the master of his duty to use reasonable care for the safety of his servants in the appliance fur*494nished them and the place where they were required to work.
The court gave liberal instructions in favor of the defendant on these points; advising the jury in the eighth instruction for the defendant that it was not bound to furnish plaintiff a truck which was absolutely safe and from which pieces of iron could not slip, but one which was reasonably safe if plaintiff exercised ordinary care; and in the ninth instruction for defendant the same rule was laid down regarding the floor, the jury being told that defendant was under no obligation to furnish plaintiff a floor which was absolutely smooth or on which the truck could not be overturned. We agree to these propositions of law, but think it was for the jury to say whether or not the floor was reasonably smooth and the truck reasonably safe when used together ; and if they were not, whether the defendant had been guilty of want of ordinary care in not making them reasonably safe. [Henry v. Railroad, 109 Mo. 488, 19 S. W. 239.]
No witness swore positively that a castor sank into the knot hole which was at the spot where the machine turned over. Many witnesses swore there was a hole there and that the machine was lying over it after it fell. It would be nearly impossible for a bystander to see a castor in the hole unless it happened to lodge there. But as the castors were two inches in diameter and the knot hole an inch and a quarter, the machine might turn over by the jostle caused by one of the castors sinking into the hole, and the castor rise out of the hole when the machine fell. In view of the testimony going to show the hole was there, that the machine was being steadily moved and without jerks, and that all at once it jostled and fell, we think the jury were entitled to infer that it was overturned by a castor getting into the hole. Juries must often reason according to probabilities; drawing an inference that the main fact in issue existed, from col*495lateral facts not directly proving but strongly tending to prove its existence. [Hudson v. Railroad, 32 Mo. App. 667, 676; Duerst v. Railroad, 163 Mo. 607, 622, 63 S. W. 827.] The vital question in such cases is the cogency of the proof afforded by the secondary facts. How likely, according to experience, is the existence of the primary fact if certain secondary facts exist? Of course, the probability that the main fact exists because the subordinate ones do, may be so weak that a conclusion to that effect will be a mere guess. This was not true in the present case. On the contrary, fair and reasonable men might believe the cause of the overturning of the truck was a castor running into the knot hole. The following cases in which the inference of negligence was sustainéd, rest on circumstances sufflcently analogous to make the decisions relevant. [Camborn v. Railroad, 165 Mo. 543, 558, 65 S. W. 745; Buesching v. Gas Light Co., 73 Mo. 219.] Our conclusion is that the court rightly submitted the question of defendant’s liability to the jury.
2. Complaint is made of the first instruction granted at plaintiff’s request, on the ground that it permitted the jury to find the truck was defective and unsafe when there was no evidence to that effect. The word “defective” might have been omitted; it is ambiguous. All the parts of the truck were complete and it was not shown to be deficient in anything it ought to have had. It should be observed that the instruction did not permit the jury to find the truck in itself was an unsafe appliance, but that it was unsafe when pushed or pulled across a floor rough and containing knot holes, and when so pushed was likely to topple over and injure plaintiff. As indicated above, the jury might well find the appliance was unnecessarily dangerous to be used on defendant’s floor. The instruction, however, is faulty in not defining the degree of danger the jury should find was incident to the use of. the truck on the *496floor. The jury should have been required to find that it was not reasonably safe instead of that it was unsafe in any degree. Indeed, they were required to make that finding in other instructions and, perhaps, on that account we would not be warranted in reversing the judgment for the omission in this one. The court rightly instructed that the measure of defendant’s duty was to use ordinary care to have the truck and floor reasonably safe. [Bowen v. Railroad, 95 Mo. 268, 8 S. W. 230.]
3. We think error was committed in the first clause of the second instruction granted for the plaintiff. This clause told the jury that due care on the part of a child does not require the judgment and thoughtfulness which would be required of an adult person under the same circumstances. The remainder of the instruction was a sufficient statement of the law in regard to the degree of care' for his own safety that plaintiff was bound to exercise. Perhaps remarks can be found in judicial opinions in cases where the injured child was very young, like the first clause of the instruction, though we do not remember having seen any containing that exact phraseology. Not only the age, but the experience and capacity of a minor, enter as factors into the degree of care he is required to observe. This boy was fifteen years old and had had a. year’s experience in the work he was doing; and though the law did not exact of him absolutely as much care as would have been required of a person of full age, neither was he absolutely excused from that degree of care. A minor employee may be old enough and possess sufficient maturity of judgment experience and emotional control, to be as capable of looking out for his safety as he is a year or two later, when of full age. The question is one of fact, not of inflexible legal rule, save when the child is of such tender years as to be presumed to be incapable of properly caring for itself. The rule on the subject has been frequently stated by the Supreme and Appellate Courts of this State, but *497in no case better than in Burger v. Railroad, 112 Mo. 238, in which the court said: “The rule is believed to be recognized in all the courts of the country, that a child is not negligent if he exercises that degree of care which under like circumstances, would reasonably be expected of one of his years and capacity.” To the same effect are Anderson v. Railroad, 81 Mo. App. 116; Thompson v. Railroad, 93 Mo. App. 548, 67 S. W. 693, and Anderson v. Railroad, 161 Mo. 411, 61 S. W. 874. All the decisions on the subject, so far as we know, take into consideration the proved capacity of the boy to understand the danger to which he was exposed, as well as his age. Now the first clause of the instruction in question stated flatly that due care on the part of a child, presumably plaintiff, did not require the judgment and-thoughtfulness that would be expected of an adult person. What was due care on his part was to be determined by the jury on all the facts going to show his age, experience and capacity.
The judgment is reversed' and the cause remanded.
All concur.