else. There are certain forms of sea-weed which are often eaten as an addition to other kinds of food. There is in all of them a certain flavour of the sea, arising, probably, from the saline matter they contain, which renders them very objectionable to some persons as articles of food, and which will, probably, always form an objection to their general use.

Now I come to speak of sugar. I have told you that starch is converted into sugar, and you will not be surprised, therefore, to find sugar present in the same places that we find starch; and if you look at the analysis of vegetable food containing starch you will find that they all contain sugar. Sugar is found in wheat, and barley, and oats; in lentils, beans, and peas. In some cases we find large quantities of sugar where we find no starch. Take, for instance, the carrot and the sweet potato. Now, sugar is soluble in water, and we find sugar more generally contained in the juices or the sap of the plant than in any other form. It also has the remarkable property of fermentation. Thus carbon, and hydrogen, and oxygen, are capable of being converted into that substance which we know by the name of alcohol; and it is during the process of the decomposition of sugar that this alcohol is produced. Therefore, you see, we can make alcohol from starch, but we must first convert the starch into sugar. Of this matter we shall speak in a subsequent part of our lectures.

The general chemical composition of sugar is the same as starch. Sugar, like starch, contains carbon as its principal ingredient, and you can demonstrate this by a very pretty experiment. If you take a strong

solution of sugar, and add to it about the same quantity of sulphuric acid, you will decompose the sugar; and the carbon, in the form of charcoal, is set free. It is in this way you can demonstrate the presence of the charcoal; and in this way that very useful material which we call blacking is manufactured. The shining

blacking is the sugared charcoal. In this way you can prove that the starch is composed of the same material as sugar, because we can convert the starch into the sugar.

Let us now direct our attention to the history of the plant in relation to sugar. During the germination of plants sugar occurs in great quantities. If we take any seeds and throw them into the ground, the little embryo in the interior begins to grow, and this process is called germination. There is a large quantity of starch surrounding the embryo, and when it begins to grow this starch is converted into sugar. Sugar is as necessary for young plants as it is for young children, and the starch must be converted into sugar in order that they may grow. Now, this process is carried on on a very large scale in the process of malting. The maltster takes the seed of barley, immerses it in water, causes the young plant to germinate, and then he roasts the young plant, seizes the sugar which was created for its use, and converts it into beer.

Then, again, we find the stems of plants, at certain seasons of the year, contain large quantities of sugar; thus the whole of the grasses, including wheat, barley, oats, rye, rice, and maize, contain sugar in their stems just as they are about to flower; and it is just at this

season of the year that the sugar-cane contains its sugar, which is used almost exclusively for man as an article of diet. But we need not confine ourselves at all to the sugar-cane. Why we get

sugar from nothing else arises out of our fiscal system: revenue being obtained from it, and sugar is not allowed to be produced in this country; and, consequently, we are obliged to eat the sugar of the sugarcane, or go without. In China they obtain sugar from the sugar Sorgho, the Sorghum saccharatum; which, like the sugar-cane, belongs to the family of grasses, and is cultivated in the north of China for the sugar it contains. Sugar has been obtained from this plant in France, and it flourishes in England. Then the maize, the plant which yields Indian corn, has been cultivated in America and Mexico, for the purpose of obtaining sugar; and when Cortes conquered Mexico, he found the natives cultivating the maize, and crushing it for sugar. The Cocos nucifera, or cocoa-nut palm, grows abundantly in the island of Ceylon, and is a principal source of sugar to the natives. They have a class of men, a caste, whose occupation it is to ascend these

Fig. 14.-The Sugar-cane. (Saccharum officinarum.)

trees, and putting over the cut blossoms of the tree a calabash, they catch the exuding juice, which is a daily article of diet in Ceylon. They call it toddy, and the men who draw it are called toddy-drawers.

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Again, at the budding season of the plant the sap contains sugar. The common osier has it; and boys, after peeling osier twigs, put them into their mouths to taste the sugar. The birch, too, in England and Scotland, is tapped for its sugar. The sap is converted, in Scotland, into an effervescing wine, which is said by those who drink it to be as good as champagne. In America, the sugar maple (Acer saccharinum) contains so large a quantity of sugar that much of the sugar consumed in the United States is obtained from it. Then plants contain sugar in their roots. The beet, the carrot, and the turnip all contain sugar. When the first Napoleon Bonaparte pursued his "continental system," as it was called, he excluded cane-sugar from the French markets, and they set to work to supply the loss, and adopted a process invented by the Germans for the extraction of sugar from the beetroot. This manufacture was protected for many years in France, but now that the trade is free the beet sugarmakers are enabled to compete with the manufacturers of sugar from the sugar-cane.

Another source of sugar in our food, is the fruit which we eat. The fig, the pear, the apple, the orange, and the great majority of our fruits would be unacceptable to us but for their sugar.

Although sugar is always sweet, and we call everything that is sweet sugar, yet there are various kinds of sugar. Sugar exists in animals as well as plants.

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Milk contains sugar, which is separated and sold uuder the name of milk sugar. The liver contains a sugarmaking principle, and we can by digesting the livers of animals in water, obtain large quantities of sugar, called liver sugar. Thus we have several kinds of sugar, and, perhaps, it will be as well just to recapitulate. First, the cane sugar, which is composed of carbon 12, hydrogen 10, and oxygen 10. This cane sugar is unfermentable, and incapable of being converted into alcohol as simple cane sugar. Cane sugar is found in the stems of plants, and in all those cases where it is procured before the flowering of plants, and in the roots of plants, so that the beet-root sugar, and the ordinary sugar that we eat from day to day is cane sugar. But the sugar from fruit is different. It is uncrystallizable, and thus differs from cane sugar. This fruit sugar is almost identical with another sugar, which, because it is formed out of starch, is called starch sugar. Now fruit sugar and starch sugar are both known to chemists by the name of glucose, or grape sugar. Fruit sugar or glucose is fermentable. The cane sugar is called sucrose, and the sugar obtained from fruit fructose, and the starch sugar glucose. Milk sugar is called lactose, whilst liver sugar, I suppose, may be called hepatose. Our ordinary sugar is sucrose. All these sugars, with

the exception of sucrose, are fermentable, and easily decomposed. If you take a little of this starch sugar, and put it into a test tube, and mix it with a little sulphate of copper, and put in some potash, you throw down a blue precipitate. Now the property of the glucose is to decompose this oxide of copper, and convert it from the blue oxide into a yellow oxide, and