As contrasted with specific or ascertained goods (Sale of Goods Act: Ont. ss. 2, 19, 51; U. K. ss. 62, 17, 52), the subject of the contract of sale may be unascertained or merely described generically.
As contrasted with existing goods owned by the seller, the subject of the contract may be future goods, that is, goods to be manufactured or acquired by the seller after the making of the contract (Ont. s. 7; U.K. ss. 62, 5).
Whereas in the case of specific goods existing at the time of the contract and owned by the seller, the parties may intend to effect either a present gale or an agreement to sell at a future time, the former of these two alternateves is excluded in the case of future_goods and in the case of other unascer-tained^2gp4js.
The Sale of Goods Act (Ont. ss. 7, 18; U. K. ss. 5, 16) provides:
7. - (3) Where by a contract of sale the seller purports to effect a present sale of future goods, the contract oper ates as an agreement to sell the goods.
18. Where there is a contract for the sale of unascertained goods, no property in the goods is transferred to the buyer unless and until the goods are ascertained. In the United States the corresponding provisions of the Uniform Sales Act are as follows:
5. - (3) Where the parties purport to effect a present sale of future goods, the agreement operates as a contract to sell the goods.
17. Where there is a contract to sell unascertained goods no property in the goods is transferred to the buyer unless and until the goods are ascertained, but property in an undivided share of ascertained goods may be transferred as provided in section 6.
6. - (1) There may be a contract to sell or a sale of an undivided share of goods. If the parties intend to effect a present sale, the buyer, by force of the agreement, becomes an owner in common with the owner or owners of the remaining shares.
(2) In the case of fungible goods [that is, goods of which any unit is from its nature or by mercantile usage treated as the equivalent of any other unit: s. 76], there may be a sale of an undivided share of a specific mass, though the seller purports to sell and the buyer to buy a definite number, weight or measure of the goods in the mass, and though the number, weight or measure of the goods in the mass is undetermined. By such a sale the buyer becomes owner in common of such a share of the mass as the number, weight or measure bought bears to the number, weight or measure of the mass. If the mass contains less than the number, weight or measure bought, the buyer becomes the owner of the whole mass and the seller is bound to make good the deficiency from similar goods unless a contrary intent appears.
Referring to s. 6, the Commissioners on Uniform State Laws (Proceedings, 1906, p. 144) say:
These provisions are new, and 6 (2), at least, probably does not express the English law. It expresses the doctrine of Kimberley v. Patchin, 1859, 19 N.Y. 330, which is supported by the weight of recent American authority, though there are adverse decisions. . . . It is to be noticed that it is provided only that title may pass under the sug-gested circumstances. The presumption would in most cases be that it did not pass because not intended to pass until separation.
See also White v. Wilks, 1813, 5 Taunt 176, 23 R.C. 252, American notes at pp. 255 ff.; and Benjamin, Sale, 5th ed. 1906, p. 338, where it is said that the American cases are in hopeless conflict.
The English rule is that if the parties have not agreed on specific goods as the subject of the contract, and a fortiori in the contract relates to goods which are not yet in existence, no property in any particular goods can pass, and the contract must be a mere agreement to sell, not a present sale. It can make no difference that the goods are so far ascertained that, the parties are agreed that they shall be taken from a specific larger bulk, if the identity of the portion so to be taken is unascertained.
"Benjamin, Sale, 5th ed. 1906, pp. 334 ff.; 25 Halsbury, Laws of England, p. 167; White v. Wilks, supra; Busk v. Davis, 1814, 2 M. & S. 397; Pletts v. Campbell,  2 Q.B. 229; Healey v. Howlett,  1 K.B. 337; Ross v. Hurteau, 1890, 18 Can. S.C.R. 713; Kidd v. Docherty. 1914, 7 S.L.R. 137, 16 D.L.R. 525; Zaiser v. Jesske, 1918, 11 Sask. L.R. 462, 43 D.L.R. 223. To the contrary is the opinion expressed in Inglis v. Richardson & Sons, 1913, 29 O.L.R. 229, 14 D.L.R. 137, that there may be a present sale of an undivided part of a larger bulk. Benjamin, (Sale, 5th ed. 1906, p. 338) is in this case incorrectly quoted as saying that the cases in England are in conflict.
The parties may agree that so soon as the goods are ascertained the property in them shall pass to the buyer, or even that the property in goods to be manfactured by the seller shall pass in an unfinished state at any stage before the completion of the manufacture.
Seath v. Moore, 1886, 11 App. Cas. 350, at pp. 370, 380, 381, 23 R.C. 257, at pp. 278, 287, 288; Laing v. Barclay,  A.C. 35, at p. 43.