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In this lecture I wish to bring before you what I have called the mineral substances of food; and sometimes these substances are called mineral food.

The table of constituents of food indicates these mineral matters of our food, and to which people, generally speaking, attach very little importance. Persons who prepare our food-cooks in the kitchen, ladies who superintend cooks, and order dinners for large families, and people who consume food from day to day, never think of asking whether food contains the right proportions of these ingredients to secure health. Yet, without these, babies get rickets, young ladies acquire crooked spines, fathers get gouty, and mothers have palpitations; and they do not, however,

think of ascribing these things to the food which has deprived them of the proper constituents of their blood. I think I can show you that this subject is a matter of great importance. I will call your attention to the table again. You will find there the mineral matters marked in by little cross lines, so that you see in cheese there are 3 lbs. in the hundred; and so, if you cast your eye down the table, you will see they are in small quantities in different substances. Now let me call attention to the flesh-forming and heat or force forming materials of our food. If you give fleshforming materials, as caseine alone, to a dog, he will die. Then take butter, which is a heat-giving material. If you feed a dog on that he will die, as though you gave him nothing. Then let us take cooked meat, with nitrogenous and fatty matter, 35 lbs. in the hundred, squeeze out of it the mineral matter, and give it to the dog, and he still dies. No matter, you may mix the caseine, and fat, and starch, and sugar, and yet the dog dies unless you give him the mineral substances about which I wish to speak more particularly in this lecture. I believe it can be proved that those who have acted upon the supposition that the flesh-forming and heat-giving materials were the only things necessary for them, and have neglected attending to these mineral constituents, have suffered in their health. Hence I have put them prominently forward, and I shall endeavour to-day to show you where you can get them, and avoid the danger of neglecting them altogether.

Now let me draw your attention to the composition of the human body. Suppose we taken a human being

weighing 154 lbs., and submit him to analysis, we should find that we should obtain 111 lbs. of water; and the next thing that would come off would be carbonic acid gas, and then there would be ammonia and sulphuretted hydrogen, and phosphoretted hydrogen, and gases of that sort: at last we should get a quantity of ashes. Now, in the water, we have oxygen and hydrogen; and in the carbonic acid gas, carbon and oxygen; and in the ammonia, nitrogen and hydrogen. In the ashes which are left, you get a variety of mineral substances,-salts, as they are called. We get phosphate of lime, carbonate of lime, fluoride of calcium, chloride of sodium, chloride of potassium, sulphate of soda, carbonate of soda, phosphate of soda, sulphate of potash, peroxide of iron, phosphate of potash, phosphate of magnesia, and silica. These are the things about which I shall have to talk to you to-day-these ashes which are left, and without which we cannot live. Now if you will persist in having only refined sugar, and the whitest flour, rejecting the bran; if you will persist in rejecting the salt, and avoiding the liquor that meat is boiled in, you may get albumen and fibrine, but none of these other substances; and then the first attack of fever or cold may prove fatal. Four men shall be travelling outside an omnibus,—one may get acute inflammation of the lungs, another bronchitis, and the other two shall come off free. Was it the riding outside of the omnibus that caused the two to fall ill? No, it was the state of their blood. They had lived somehow irregularly; somehow their bodies had been deprived of their proper constituents. So you may find half a

dozen children, all exposed to the contagion of scarlet fever;-two take it; one dies, and the other four are free: but the two that have caught it have lived in such a way that their blood has readily taken in the contagion; and the one that has died has got into a condition which has produced death. Hence the importance of attending to these subjects thoroughly; not getting a little knowledge of them, but a knowledge of what is necessary to the feeding of children and the feeding of men. If we do not attend to these things, we shall, somehow or other, suffer.

Now I shall take up these constituents as I have mentioned them, and which is very much according to their importance. You cannot expect me to go into an exhaustive chemical analysis of this subject, and I may just say that chemical science is not in a condition to do so. Neither the chemist nor the physiologist has gone into the phenomena of the action of these substances in our system.

The first substance I shall take up is chloride of sodium, common salt. This is the only substance which we take directly from the mineral kingdom. All the other salts we get through plants or animals. But salt is a substance which we take direct from nature, and thus we satisfy the cravings of our system for this substance. Now this salt is composed of two elements-of chlorine, a gas, and of sodium, a metal. Chlorine is a most suffocating and even dangerous gas to experiment with. Sodium is a metal so easily oxidised in the air, that we are obliged to keep it in naphtha, and when we throw it into warm water it takes fire just as potassium does. Now we may

well wonder that these two substances, so energetic and even dangerous when separated, should be so benignant and beneficial when united. Chlorine is not only a suffocating gas, but, like oxygen, it is a supporter of combustion, and has very powerful affinities. It can be easily separated from common salt by mixing it with peroxide of manganese, and pouring on them a little sulphuric acid. The greenish fumes that arise are chlorine. On account of its energetic chemical action it is used as a disinfectant, a deodoriser, and a bleaching agent. It is used by the paper maker and the calicoprinter for the purposes of bleaching. It acts upon colouring matter by decomposing it and uniting with the hydrogen it contains, forming hydrochloric acid. In this way it acts as a deodoriser. Most of the disagreeable smells given off by decaying animal and vegetable matter depend on compounds of hydrogen, and the chlorine, uniting with this substance, destroys them. This is the substance, then, which, combining with sodium, forms common salt.

Salt determines the life and forms of both plants and animals in the ocean. Withdraw the salt from the ocean, and you will have none of the life which now exists there. Herrings, mackerel, codfish, and all the forms of fish that we get out of the sea, would retire, and we should have in their stead the fish of our rivers, such as roach, carp, dace, and bream. Instead of the seaweeds, we should have the plants of our fresh waters, the valsineria, the potamogetons, the anacharis, and the water-lilies. In this you will see how this salt influences life and the forms of life. We get it for our own use from the sea, and from those deposits of