THE PRODROMUS 225 



thus, feathery alum, different kinds of veins which I have 

 observed in the fissures of rocks ; or to dendrites, as those forms 

 of plants which are seen in the chinks of stones, except that 

 certain ramifications in an agate which I have seen, whose 

 trunks rested on the surface of the outer lamella but whose 

 branches spread throughout the substance of the inner lamella, 

 are merely superficial ; or to angular bodies, as the crystals of 

 p. 24. mountains, the angular bodies of iron and copper, cubes ^ of 

 marcasites, diamonds, amethysts, and the like ; or to replace- 

 ments, as variegated marbles of every kind, granites, dendrites, 

 petrified mollusks, crystalline substances, metallic plants, and 

 many similar bodies filling the places of bodies which have 

 been destroyed. 



Other solids are produced by accretion from the internal 

 fluid ; and these are due either to simple replacements, as fat, 

 the callus uniting broken bones, the cartilaginous substance 

 joining severed tendons, the tissues which chiefly form the sub- 

 stance of the viscera, the medulla in both plants and animals ; 

 or to fibrous growths, as the fibrous parts of plants, the nerve 

 fibres and muscle fibres in animals, also, which are all solid 

 bodies and are naturally enclosed, for the most part, within solids. 



If, therefore, every solid has had its accretions, at any rate, 

 from a fluid, if bodies similar to one another in all respects were 

 also produced in a similar way, and if of two contiguous solids 

 that one first became hard which exhibits on its own surface the 



naire Encydopedique des Sciences Medicales, Tome Neuvifeme (Paris, 1868), pp. 221-225. 

 Steno refers, of course, to the fossil, which is briefly alluded to in the work mentioned, p. 225 : 

 " Le b^zoard fossile ^tait composd de masses globuleuses de carbonate de chaux, rdunies en 

 couches concentriques." 



A fuller description of the stone is quoted by Maar {op. cit., Vol. II, p. 336) from the 

 Dictionnaire Raisonne Universel d'Histoire Naturelle, by Valmont-Bomare, 3d ed., Lyon, 

 1791, Vol. II, p. 230: 



"Une pierre arrondie, de couleur cendr^e, compos^e de couches concentriques, friables, 

 depuis la grosseur d'une aveline jusq'k celle d'un oeuf d'oie. Au centre de cette pierre est 

 quelquefois un grain de sable, une petite coquille, ou un morceau de charbon de terre. Une 

 de ces matieres a servi de noyau, de point d'appui, et venant k rouler sur des terres molles, 

 k demi-trerapdes, elle s'est ainsi accrue par couches roul^es comme une pelotte de rubans." 



1 For ubi of the Florentine edition read cubi, with Maar, op. cit.. Vol. II, p. 195. By 

 "cubes of marcasite " Steno, in common with the older scientists, means pyrites. Marcasite 

 has the same chemical composition as pyrites, FeSj, being iron disulphide. But marcasite 

 crystallizes in orthorhombic form, whereas pyrites crystallizes in the cubic system. See H. 

 N. Stokes, On Pyrite and Marcasite, in Bulletin of United States Geological Survey, No. 186 

 (1901). 



