INTRODUCTION. xiii. 



their clarity is as crystal to mud in comparison with those of his predecessors — 

 and of most of his successors for over two hundred years. As an indication of 

 his grasp of some of the wider aspects of geological phenomena we reproduce, 

 in Appendix A, a passage from De Oriu et Causis, which we believe to be the 

 first adequate declaration of the part played by erosion in mountain sculpture. 

 But of all of Agricola's theoretical views those are of the greatest interest which 

 relate to the origin of ore deposits, for in these matters he had the greatest 

 opportunities of observation and the most experience. We have on page io8 

 reproduced and discussed his theory at considerable length, but we may repeat 

 here, that in his propositions as to the circulation of ground waters, that ore 

 channels are a subsequent creation to the contained rocks, and that they 

 were filled by deposition from circulating solutions, he enunciated the founda- 

 tions of our modem theory, and in so doing took a step in advance greater than 

 that of any single subsequent authority. In his contention that ore channels 

 were created by erosion of subterranean waters he was wrong, except for 

 special cases, and it was not until two centuries later that a further step in 

 advance was taken by the recognition by Van Oppel of the part played by 

 fissuring in these phenomena. Nor was it until about the same time that the 

 filling of ore channels in the main by deposition from solutions was generally 

 accepted. While Werner, two hundred and fifty years after Agricola, is 

 generally revered as the inspirer of the modem theory by those whose reading 

 has taken them no farther back, we have no hesitation in asserting that of the 

 propositions of each author, Agricola's were very much more nearly in 

 accord with modem views. Moreover, the main result of the new ideas 

 brought forward by Werner was to stop the march of progress for half a 

 century, instead of speeding it forward as did those of Agricola. 



In mineralogy Agricola made the first attempt at systematic treatment 

 of the subject. His system could not be otherwise than wrongly based, 

 as he could scarcely see forward two or three centuries to the atomic theory 

 and our vast fund of chemical knowledge. However, based as it is upon 

 such properties as solubility and homogeneity, and upon external character- 

 istics such as colour, hardness, &c., it makes a most creditable advance 

 upon Theophrastus, Dioscorides, and Albertus Magnus — his only predecessors. 

 He is the first to assert that bismuth and antimony are true primary metals ; 

 and to some sixty actual mineral species described previous to his time he 

 added some twenty more, and laments that there are scores unnamed. 



As to Agricola's contribution to the sciences of mining and metal- 

 lurgy, De Re Metallica speaks for itself. While he describes, for the first 

 time, scores of methods and processes, no one would contend that they 

 were discoveries or inventions of his own. They represent the accumulation 

 of generations of experience and knowledge ; but by him they were, for the 

 first time, to receive detailed and inteUigent exposition. Until Schliiter's 

 work nearly two centuries later, it was not excelled. There is no measure by 

 which we may gauge the value of such a work to the men who followed in 

 this profession during centuries, nor the benefits enjoyed by humanity 

 through them. 



