Moreover, it will be in consonance with my subject, and of practical use as well, if I advise you in one course of the order observed in this book about minerals. This order is different to that which has been pursued by others. First the metals will be treated, and these are not of one kind but distributed according to their own essences and also according to the uses which they supply for men. Some of these are fragile, others durable, and in proportion they are subservient to human convenience. So, also, some gems are useful to man not in their metallic form, but in order that they may be worn, or minister to human health. Such as these are the sapphire, the magnet, the cornelian, etc. These are created in a special form, so that a man may be able easily to carry them about with him. Then, again, there is another kind of stones which man does not use as he uses a metal or a gem, but which he employs for building houses or other receptacles necessary for human life. Further still, another genus is composed of Salts, of more than one species, which are neither metals, nor gems, nor stones, which also are useful for purposes which are subserved neither by metals, gems, nor stones. Moreover, a special order has been assigned to springs, some of which do good to the internal organs of the body, others help it externally. Some are warm and others cold, some acid whilst others are sweet. There are so many different species that one could not exhaustively define them. There are also different kinds of marcasites, two, for example, coloured like gold and silver. But there are very many species in which God has held several things in reserve, which also are put in man's hand that he may seek what he will, and extract from them whatever God has conferred upon them. There are also things that belong to a different genus; talc, of which there are four sorts, red, white, black, and clay-coloured. This genus comprises neither metals, gems, stones, salts, springs, nor marcasites, but something special and by itself. It gives also sand, with a supply of silver. Of this more need not be said than that it is useful for buildings and for making cements. There is also another genus given to us, namely, sulphureous minerals, of which there are two, the clay-coloured and the black; and there are also carabæ.
There are more of this nature, and especially one genus which is allied to no other, in which the health of men is to be found, and it can also be applied to external uses. Besides this there is another genus not like the above-mentioned, namely, corals. Of these the red and the white are well known. Other colours are also found, and forms such as are described in the paragraphs devoted to the subject. Moreover, after these there remains another genus, beyond what is natural, which, by the will of Nature, becomes an instrument of various forms and properties, as the eagle-stone and the buccinæ, cockles, patellæ, etc. The origin of these from the element of the water, you can find in my succeeding paragraph. From the element of water too, many kinds of fruits are produced; and though I shall only describe those which are known to me, I have found out much more, because the lower globe and the higher sphere, in all their parts, above, below, and on every
