"Cottonseed oil!" murmured Mary, recognizing an old friend. "We often use it to fry things. It's good on lettuce, too. But somehow I never thought that it was really made from the seeds of cotton." "We often accept terms without thinking much about them, don't we?" Captain Dillingham agreed. "But cottonseed oil is a genuine by-product of cotton." "What is a by-product?" smiled Mary ingenuously. "A by-product is something made from the leavings," put in Carl without hesitation. "Hash is a by-product of corned beef." A laugh greeted the assertion. "Technically speaking a by-product is something that is turned to account from what would otherwise have been waste. Every person who manufactures on a large scale tries to think what he can do with what is left after he has made the thing he started out to make. This he does for two reasons: first he wishes to turn back into money every ounce of material for which he has paid; secondly he desires to get rid of stuff which would otherwise accumulate and (if not combustible) force him into the added expense of carting it away. In other words he seeks to convert his waste into an asset instead of a liability. Therefore all big producers tax their brains to invent things that can be made from their waste, and such commodities are called by-products. Many of these things require no ingenuity for frequently they are articles much needed in other trades. Masons, for example, are only too thankful to have the hair taken from tanned leather to hold their plaster together; and those who dry and salt fish can easily turn the fish skins into glue. The by-products of great packing houses and tanneries are legion. Often such dealers will have at hand such a supply of usable stuff that they will establish other factories where their unused materials can be converted into cash. The sale of these products often increases very materially the profits of a business. Such a product is cottonseed oil. As millions more seeds mature each year than can possibly be used for planting why not turn them to account? Often there are from sixty-five to seventy-five pounds of seeds to a hundred pounds of cotton. Think how rapidly they would accumulate if something could not be done with them. During the war when we were unable to get olive oil from Italy and fats of all kinds were scarce we were thankful enough to fall back on the cottonseed oil made in our own country. At the oil mills machines are ready to clean the cotton seeds of lint, hull them, separate hull from kernel, and press the oil from the kernel itself. This oil is then bottled, labelled, and shipped for sale, making quite an independent little industry, you see. What is left of the crushed kernels is removed from the hydraulic presses and is remolded into small cakes to be used for----" he paused, glancing quizzically toward Carl and Mary. "For what?" the boy asked. "Guess!" "I've not the most remote idea," Carl returned. "Nor I!" echoed Mary.