XXVIII LIFE AND WORKS OF NICOLAUS STENO 



drawing nourishment on that side where they stick to their matrix; 

 it was likewise a current belief that if crystals were removed from the 

 spot, where they were fixed, others would form themselves at the 

 same spot. The explanation which Steno offered of the formation of the 

 crystals was quite different from the latter theory; being based upon 

 ingenious observations and conclusions it is once more the explanas 

 tion, which holds good to this very day. Steno admitted that he was 

 quite unable to determine the manner of the first delineation of cry? 

 stals, but he maintained that crystals only increase in size in fluids 

 and that the growth, when once begun, will continue through the me* 

 dium of new crystalline matter, materia crystallina, being put to the 

 planes of already delineated crystals. Steno, however, did not rest 

 satisfied with this. After a thorough examination of different crystals 

 — crystals of quartz, iron ore, pyrites and others — he showed that 

 every crystallizable substance crystallizes in its own particular form, 

 of which crystal forms he gave very exact descriptions with illustra* 

 tions, being likewise the first to mention that the opposite planes of 

 crystals are always parallel to one another. Steno also made numerous 

 other valuable remarks and observations concerning crystals, which 

 it would take too long to enumerate in this place. 



Not only did Steno's principal work on geology never appear; but 

 even of smaller writings on geological subjects only two short Letters 

 to Cosimo III are extant, containing descriptions of the grottos at 

 Gresta and Moncodine, which were, in fact, not published till long 

 after Steno's death. They are interesting, in that Steno here points 

 out that rock«crystal can not be indurated ice, at that time a not un* 

 common belief; but they are also remarkable because of the natural 

 explanation which Steno gives of the fact that the temperature inside 

 a grotto is so much lower than the temperature outside in summer 

 time and vice versa in winter time, thus rendering the doctrine of the 

 antiperistasis superfluous. 



Steno's work in the service of science did not end abruptly ; yet within 

 a few years it rapidly diminished in quantity as well as in merit, until 

 at last it ceased altogether, when he was only thirty*five years of age. 



