170 FOREWORX) 



and a half, there was no writer upon natural science before the 

 eighteenth century that in accuracy of observation, in cogency of 

 reasoning, or in discrimination of judgment might be compared with 

 the "learned Dane." In some measure Steno reflected, of course, 

 the crude notions of his time. Thus we find him adopting, though 

 apparently with some reserve, the doctrine of the four elements, fire, 

 earth, air, and water. In the main, however, if we exclude the prolix 

 introduction addressed " to the Most Serene Grand Duke " and the 

 weak conclusion intended to prove the orthodoxy of his position, the 

 Prodromus with but moderate changes may be made to harmonize 

 with the science of the twentieth century. We must attribute it 

 largely to the closeness of his observation of Nature and to his dis- 

 criminating judgment, that Steno was not lured into wild speculations, 

 as were so many in his time. One of his statements might well be 

 printed in large letters and placed upon the walls of our laboratories 

 and lecture rooms, as a warning to those who undertake scientific 

 investigation. " The nurse of doubts," says Steno, " seems to me to 

 be the fact that in the consideration of questions relating to nature 

 those points which cannot be definitely determined, are not dis- 

 tinguished from those which can be settled with certainty" (p. 213). 

 How much trouble would be saved if to-day scholars had this point 

 oftener in mind ! 



( The form of Steno's essay is geometrical, and this is responsible 

 ifor the almost unintelligible title and the correlation of subjects which, 

 interpreted in the elaborate differentiation of twentieth century 

 science, appear somewhat incongruous. As stated in the introduction, 

 the Prodromus is divided into four parts. The first of these contains 

 among other things an inquiry into the origin of fossils. The second 

 part is stated to be : " Given a substance possessed of a certain figure, 

 and produced according to the laws of nature, to find in the substance 

 itself evidences disclosing the place and manner of its production." 

 In like geometrical form the third part discusses solids which are con- 

 tained within solids. The concluding portion of the essay is largely 

 a consideration of the prehistoric geological changes which Steno 

 was able to read in the rocks of Tuscany. 



The broad outlines of the Cartesian conception of matter were 

 adopted by Steno, who regarded a natural body as an aggregate of 

 imperceptible particles subject to the action of forces such as proceed 

 from a magnet, from fire, or sometimes from light. A fluid differed 



