INTRODUCTION. 2$ 



in all directions with the earth's surface, at which they appear 

 as thermal springs. Kircher follows Aristotle's view of the 

 origin of springs, lakes, and rivers. Books VI., VII., and 

 VIII. treat of the earth's composition, but offer no descrip- 

 tion of the different rocks such as one might expect; they 

 describe in diffuse style the salts that occur in the earth, and 

 the constitution and uses of sand, clay, cultivated soil, etc. 

 The consolidation of loose material into rock is ascribed 

 to a petrifying force (vis lapidified] inherent in the earth, f 

 while a form-giving force (Spiritus architectonicus or plasticus) 

 is said to produce all kinds of shapes and figures, for example,; 

 crystals, precious stones, stalactites, and fossils. 



Book X. is devoted to mines and minerals. Kircher relates 

 that through the medium of Jesuit priests, he put several 

 questions to the miners at Neusohl in Hungary. Some of 

 these referred to the conditions of temperature in the mines 

 whether the heat increased as greater depths were reached 

 below the surface, and if there were any signs of subterranean 

 fire. The answer from Schemnitz was that in a well-ventilated 

 mine the heat was scarcely perceptible, but that with poor 

 ventilation the mines were always warm. Johann Schapel- 

 mann, an official of the mines in Herrngrund, reported as 

 follows: "In dry mines the temperature steadily increases 

 in proportion to the depth below the surface ; where water 

 lies, the heat is less ; it is greatest in the parts of the mines 

 where marcasite occurs." This is the first observation of the 

 steady increase of temperature with added depth. 



In spite of its many weaknesses and inaccuracies, Kircher's 

 Mundus subterraneus must always command a high place in 

 the literature as the first effort to describe the earth from a 

 physical standpoint. It was followed in 1672 by the publi- 

 cation of the Geographia generalis of Varenius, a work far 

 exceeding that of Kircher in critical insight and methodical 

 treatment. It is valued as the fundamental work in the 

 domain of geophysics. 



Nikolaus Steno 1 was one of the most enlightened geologists of 



1 Nikolaus Steno was born 1638 at Copenhagen, studied medicine and 

 anatomy at Copenhagen and Paris, travelled in Holland, France, and 

 Germany, and settled in Padua. He was called to Florence to be house- 

 physician to the Grand Duke Ferdinand II., and was afterwards the tutor 

 of the sons of Cosmo. Steno then accepted an invitation sent by Christian 

 V. of Denmark, to return to Copenhagen as Professor of Anatomy ; but 



