



INTRODUCTION. XXT 



*< Upon handling different fossils, we soon perceive (to 

 use a familiar expression) that some are softer than others. 

 For instance, a piece of gypsum is much softer to the feel 

 than a piece of quartz. This difference is better observed 

 when we make use of some instrument fit for the purpose*. 

 This is what is termed by mineralogists the investigation of 

 hardness ; and, with respect to this property, we shall divide 

 solid fossils into hard, semi-hard, soft, and very soft. 



" A fossil is called hard which cannot be marked or 

 scratched by the knife, or rather which emits sparks, being 

 struck by the steel. This degree of hardness is to be found 

 only in fossils which are perfectly brittle (Sprode). Hard 

 fossils are also distinguished into those which are affected by 

 the file; those which are but in a small degree; and those 

 which are not in the least. To the last belong the diamond, 

 ruby, and emerald ; in the second may be placed the topaz, 

 rock-crystal, amethyst, flint, chalcedony, carnelian, &c. which 

 yield a little to the file 5 among those on which the file takes 

 effect, are white copper- ore, micaceous iron-ore, hematite, 

 most compact iron stones, red and brown tin crystals, most 

 shining grey cobalt ores (speis kobolt), arsenical and sul- 

 phureous pyrites, c. 



" Semi-hard is applied to a solid fossil which does not emit 

 fire with steel, and which may be marked or scratched by the 

 knife. Of this nature are fahlers, red copper-ore, sparry 



* " The instruments employed by mineralogists in this investigation are, the 

 'knife for semi-hard and soft fossils, the steel for those which are hard, and the 

 file, for fossils perfectly hard. The knife may also be used to judge of the 

 streak and ductility. In order to possess a complete mineralogical apparatus, it 

 will suffice to add to these instruments a magnifier, which will often be wanted 

 to determine the exterior form and fracture, and which may be well observed 

 with a single glass; 2. a small phial ofaquafortis, the use of which I shall dis- 

 close in the last chapter; 3. a loadstone, which for convenience may be so ma- 

 naged as to serve at the same time for a steel. If there be also added a blow- 

 pipe, in order to make essays speedily upon minerals with the assistance of fire, 

 we shall possess all to be desired. These articles may all be met with, well 

 made and adapted, at Mr. Schubert's, Mechanic to the Academy of Mines, 

 Freyberg." 



