The following opinion was filed April 5, 1921:

The defendant argues the question of plaintiffs’ contributory negligence at great length. It has no place in the case, and the court properly set aside the answer of the jury finding plaintiffs guilty of contributory negligence, both on the ground' that there was no evidence, as he found, to sustain it, and on the ground that it was not .an issue in the case. If plaintiffs gave defendant directions to sell the barley it became its duty to exercise reasonable diligence to execute such directions. If no directions were given, that would constitute no negligence on the part of plaintiffs affecting defendant’s liability, though the failure to give such directions might relieve defendant of liability, not because of contributory negligence but because no duty was placed upon it to act.

We have carefully examined the evidence and reach the conclusion that it sustains the finding that plaintiffs ordered the barley sold on the 17th of April-, and that in the exer*346cise of reasonable diligence defendant could have shipped it within twenty-one days. That would have been by May 8th. There is no evidence as to the market price of barley on May 8th. The nearest dates are May 2d, when barley was worth from $1.68 to $1.79 at Milwaukee, and on May 15th, when it sold for $1.38 to $1.42 at the same place. The jury evidently took a mean between these prices, as they found the damages about thirty-two cents per bushel. This added to $1.23, at which it sold, would make the price $1.55 per bushel. As the market price at or near May 8th is not in evidence, the finding of the jury is not supported by sufficient evidence in view of the sharply fluctuating market.

Since all the other issues are determined upon competent evidence, the cause will be remanded with directions to take evidence as to the market value of barley on May 8, 1918, if the parties will not stipulate its value, and to enter judgment for plaintiffs for the price per bushel so found or stipulated, with interest thereon from July 13, 1918, when returns on the sale were had and when defendant offered to pay plaintiffs $1.23 per bushel for the barley, which they refused to accept, demanding more.

It is held in Laycock v. Parker, 103 Wis. 161, 185 et seq., 79 N. W. 327, that when the amount of a demand can be fairly ascertained by reference to market prices, not necessarily by definite quotátions on the -board of trade, interest is allowable from the time of demand. In such case the law implies a promise to pay the whole amount when due and that if it is not paid legal interest can be recovered, because the defendant is enriched to that extent by the use of the money withheld and the plaintiff is deprived of the value of the use thereof which rightly belongs to him. Under the agreement between the parties the law implied that defendant would pay plaintiffs when it received returns on the sale of the barley. The case, therefore, irrespective of *347the demand that was made for more than $1.23 per bushel, falls within the class mentioned in State v. Milwaukee, 158 Wis. 564, on p. 574 (149 N. W. 579). It is there said:

“But where the time of payment is fixed by contract or by law and the amount to be paid is easily ascertainable and the duty to pay plain, no demand is necessary to start the running of interest, whether the claim be against an individual or a municipality.” Citing Laycock v. Parker, 103 Wis. 161, 79 N. W. 327; Land, L. & L. Co. v. Oneida Co. 83 Wis. 649, 53 N. W. 491; Travelers’ Ins. Co. v. Fricke, 99 Wis. 367, 375, 74 N. W. 372, 78 N. W. 407; State v. McFetridge, 84 Wis. 473, 530, 531, 54 N. W. 1, 998.

By the Court. — Judgment reversed, and cause remanded for further proceedings as directed in the opinion.

A motion for a rehearing was denied, with $25 costs,- on May 31, 1921.