On the Origin of Metals, he says (De Ortu, p. 71): "Having now refuted the opinions of others, I must explain what it really is from which metals are produced. The best proof that there is water in their materials is the fact that they flow when melted, whereas they are again solidified by the cold of air or water. This, however, must be understood in the sense that there is more water in them and less 'earth'; for it is not simply water that is their substance but water mixed with 'earth.' And such a proportion of 'earth' is in the mixture as may obscure the transparency of the water, but not remove the brilliance which is frequently in unpolished things. Again, the purer the mixture, the more precious the metal which is made from it, and the greater its resistance to fire. But what proportion of 'earth' is in each liquid from which a metal is made no mortal can ever ascertain, or still less explain, but the one God has known it, Who has given certain sure and fixed laws to nature for mixing and blending things together. It is a juice (succus) then, from which metals are formed; and this juice is created by various operations. Of these operations the first is a flow of water which softens the 'earth' or carries the 'earth' along with it, thus there is a mixture of 'earth' and water, then the power of heat works upon the mixtures so as to produce that kind of a juice. We have spoken of the substance of metals; we must now speak of their efficient cause.... (p. 75): We do not deny the statement of Albertus Magnus that the mixture of 'earth' and water is baked by subterranean heat to a certain denseness, but it is our opinion that the juice so obtained is afterward solidified by cold so as to become a metal.... We grant, indeed, that heat is the efficient cause of a good mixture of elements, and also cooks this same mixture into a juice, but until this juice is solidified by cold it is not a metal.... (p. 76): This view of Aristotle is the true one. For metals melt through the heat and somehow become softened; but those which have become softened through heat are again solidified by the influence of cold, and, on the contrary, those which become softened by moisture are solidified by heat."
On the Origin of Compounds, he states (De Ortu, p. 80): "There now remain for our consideration the compound minerals (mistae), that is to say, minerals which contain either solidified juice (succus concretus) and 'stone,' or else metal or metals and 'stone,' or else metal-coloured 'earth,' of which two or more have so grown together by the action of cold that one body has been created. By this sign they are distinguished from mixed minerals (composita), for the latter have not one body. For example, pyrites, galena, and ruby silver are reckoned in the category of compound minerals, whereas we say that metallic 'earths' or stony 'earths' or 'earths' mingled with juices, are mixed minerals; or similarly, stones in which metal or solidified juices adhere, or which contain 'earth.' But of both these classes I will treat more fully in my book De Natura Fossilium. I will now discuss their origin in a few words. A compound mineral is produced when either a juice from which some metal is obtained, or a humour and some other juice from which stone is obtained, are solidified by cold, or when two or more juices of different metals mixed with the juice from which stone is made, are condensed by the same cold, or when a metallic juice is mixed with 'earth' whose whole mass is stained with its colour, and in this way they form one body. To the first class belongs galena, composed of lead juice and of that material which forms the substance of opaque stone. Similarly, transparent ruby silver is made out of silver juice and the juice which forms the [Pg 52]substance of transparent stone; when it is smelted into pure silver, since from it is separated the transparent juice, it is no longer transparent. Then too, there is pyrites, or lapis fissilis, from which sulphur is melted. To the second kind belongs that kind of pyrites which contains not only copper and stone, but sometimes copper, silver, and stone; sometimes copper, silver, gold, and stone; sometimes silver, lead, tin, copper and silver glance. That compound minerals consist of stone and metal is sufficiently proved by their hardness; that some are made of 'earth' and metal is proved from brass, which is composed of copper and calamine; and also proved from white brass, which is coloured by artificial white arsenic. Sometimes the heat bakes some of them to such an extent that they appear to have flowed out of blazing furnaces, which we may see in the case of cadmia and pyrites. A metallic substance is produced out of 'earth' when a metallic juice impregnating the 'earth' solidifies with cold, the 'earth' not being changed. A stony substance is produced when viscous and non-viscous 'earth' are accumulated in one place and baked by heat; for then the viscous part turns into stone and the non-viscous is only dried up."
The Origin of Juices. The portion of Agricola's theory surrounding this subject is by no means easy to follow in detail, especially as it is difficult to adjust one's point of view to the Peripatetic elements, fire, water, earth, and air, instead of to those of the atomic theory which so dominates our every modern conception. That Agricola's 'juice' was in most cases a solution is indicated by the statement (De Ortu, p. 48): "Nor is juice anything but water, which on the other hand has absorbed 'earth' or has corroded or touched metal and somehow become heated." That he realized the difference between mechanical suspension and solution is evident from (De Ortu, p. 50): "A stony juice differs from water which has abraded something from rock, either because it has more of that which deposits, or because heat, by cooking water of that kind, has thickened it, or because there is something in it which has powerful astringent properties." Much of the author's notion of juices has already been given in the quotations regarding various minerals, but his most general statement on the subject is as follows:—(De Ortu, p. 9): "Juices, however, are distinguished from water by their density (crassitudo), and are generated in various ways—either when dry things are soaked with moisture and the mixture is heated, in which way by far the greatest part of juices arise, not only inside the earth, but outside it; or when water running over the earth is made rather dense, in which way, for the most part the juice becomes salty and bitter; or when the moisture stands upon metal, especially copper, and corrodes it, and in this way is produced the juice from which chrysocolla originates. Similarly, when the moisture corrodes friable cupriferous pyrites an acrid juice is made from which is produced vitriol and sometimes alum; or, finally, juices are pressed out by the very force of the heat from the earth. If the force is great the juice flows like pitch from burning pine ... in this way we know a kind of bitumen is made in the earth. In the same way different kinds of moisture are generated in living bodies, so also the earth produces waters differing in quality, and in the same way juices."
Conclusion. If we strip his theory of the necessary influence of the state of knowledge of his time, and of his own deep classical learning, we find two propositions original with Agricola, which still to-day are fundamentals:
(1) That ore channels were of origin subsequent to their containing rocks; (2) That ores were deposited from solutions circulating in these openings. A scientist's work must be judged by the advancement he gave to his science, and with this gauge one can say unhesitatingly that the theory which we have set out above represents a much greater step from what had gone before than that of almost any single observer since. Moreover, apart from any tangible proposition laid down, the deduction of these views from actual observation instead of from fruitless speculation was a contribution to the very foundation of natural science. Agricola was wrong in attributing the creation of ore channels to erosion alone, and it was not until Von Oppel (Anleitung zur Markscheidekunst, Dresden, 1749 and other essays), two centuries after Agricola, that the positive proposition that ore channels were due to fissuring was brought forward. Von Oppel, however, in neglecting channels due to erosion (and in this term we include solution) was not altogether sound. Nor was it until late in the 18th century that the filling of ore channels by deposition from solutions was generally accepted. In the meantime, Agricola's successors in the study of ore deposits exhibited positive retrogression from the true fundamentals advocated by him. Gesner, Utman, Meier, Lohneys, Barba, [Pg 53]Rössler, Becher, Stahl, Henckel, and Zimmerman, all fail to grasp the double essentials. Other writers of this period often enough merely quote Agricola, some not even acknowledging the source, as, for instance, Pryce (Mineralogia Cornubiensis, London, 1778) and Williams (Natural History of the Mineral Kingdom, London, 1789). After Von Oppel, the two fundamental principles mentioned were generally accepted, but then arose the complicated and acrimonious discussion of the origin of solutions, and nothing in Agricola's view was so absurd as Werner's contention (Neue Theorie von der Entstehung der Gänge, Freiberg, 1791) of the universal chemical deluge which penetrated fissures open at the surface. While it is not the purpose of these notes to pursue the history of these subjects subsequent to the author's time, it is due to him and to the current beliefs as to the history of the theory of ore deposits, to call the attention of students to the perverse representation of Agricola's views by Werner (op. cit.) upon which most writers have apparently relied. Why this author should be (as, for instance, by Posepny, Amer. Inst. Mining Engineers, 1901) so generally considered the father of our modern theory, can only be explained by a general lack of knowledge of the work of previous writers on ore deposition. Not one of the propositions original with Werner still holds good, while his rejection of the origin of solutions within the earth itself halted the march of advance in thought on these subjects for half a century. It is our hope to discuss exhaustively at some future time the development of the history of this, one of the most far-reaching of geologic hypotheses.
[2] The Latin vena, "vein," is also used by the author for ore; hence this descriptive warning as to its intended double use.
[Pg 56][3] The endeavour to discover the origin of the compass with the Chinese, Arabs, or other Orientals having now generally ceased, together with the idea that the knowledge of the lodestone involved any acquaintance with the compass, it is permissible to take a rational [Pg 57]view of the subject. The lodestone was well known even before Plato and Aristotle, and is described by Theophrastus (see [Note 10, p. 115].) The first authentic and specific mention of the compass appears to be by Alexander Neckam (an Englishman who died in 1217), in his works De Utensilibus and De Naturis Rerum. The first tangible description of the instrument was in a letter to Petrus Peregrinus de Maricourt, written in 1269, a translation of which was published by Sir Sylvanus Thompson (London, 1902). His circle was divided into four quadrants and these quarters divided into 90 degrees each. The first mention of a compass in connection with mines so far as we know is in the Nützlich Bergbüchlin, a review of which will be found in [Appendix B]. This book, which dates from 1500, gives a compass much like the one described above by Agricola. It is divided in like manner into two halves of 12 divisions each. The four cardinal points being marked Mitternacht, Morgen, Mittag, and Abend. Thus the directions read were referred to as II. after midnight, etc. According to Joseph Carne (Trans. Roy. Geol. Socy. of Cornwall, Vol. II, 1814), the Cornish miners formerly referred to North-South veins as 12 o'clock veins; South-East North-West veins as 9 o'clock veins, etc.
[Pg 65][4] Crudariis. Pliny (XXXIII., 31), says:—"Argenti vena in summo reperta crudaria appellatur." "Silver veins discovered at the surface are called crudaria." The German translator of Agricola uses the term sylber gang—silver vein, obviously misunderstanding the author's meaning.
[Pg 68][5] It might be considered that the term "outcrop" could be used for "head," but it will be noticed that a vena dilatata would thus be stated to have no outcrop.
[Pg 70][6] It is possible that "veinlets" would be preferred by purists, but the word "stringer" has become fixed in the nomenclature of miners and we have adopted it. The old English term was "stringe," and appears in Edward Manlove's "Rhymed Chronicle," London, 1653; Pryce's, Mineralogia Cornubiensis, London, 1778, pp. 103 and 329; Mawe's "Mineralogy of Devonshire," London, 1802, p. 210, etc., etc.