458 FLINT 



monly referred to the presence of organic matter, derived probably from the associated 

 fossils. Although sufficiently hard to strike copious sparks with stool, flint is very 

 easily broken, splitting with a flat conchoidal fracture, usually dull on the surface. 

 It is feebly translucent, and has so fine and homogeneous a texture as to bear polishing, 

 but possesses little lustre. 



Flint is found chiefly in the form of nodular masses, of very irregular and frequently 

 fantastic shapes ; and of various sizes up to a foot in diameter. These masses occur 

 embedded in calcareous, never in siliceous strata; and are especially abundant in the 

 upper beds of the chalk, which have houcobeen termed ' Chalk-with-flints.' Although 

 occasionally arranged in layers running across the plane 'of bedding, as in tho 

 ' potstones ' of Norfolk, yet as a rule the nodules have a notable tendency to dispose 

 themselves in lines parallel to the direction of tho stratification ; occasionally they 

 occur so close together as to unite, and thus form continuous horizontal bands or flat 

 tabular masses. 



Externally the flint nodules are usually coated with a white opaque crust, appa- 

 rently siliceous ; whilst internally they are often hollow, the cavities sometimes 

 containing pulverulent silica, and sometimes being lined with chalcedony, or with 

 crystals of iron pyrites or other minerals ; whilst almost universally they enclose tho 

 remains of some marine organism, commonly a sponge. Indeed, the study of the 

 microscopic structure of flint has led Dr. Bowerbank to the conclusion that all flints, 

 both nodular and tabular, contain the remains of spongeous tissue, which appears to 

 have acted as a nucleus or centre of attraction around which the silica was deposited 

 from solution. 



Flints when first quarried are exceedingly brittle, and are commonly humid when 

 broken, but by exposure to the air they gradually acquire toughness ; hence, when 

 used as road-material, they should never be laid down on immediate removal from the 

 quarry. 



Flints calcined and ground to a powder enter into the composition of all kinds of 

 fine pottery, and were formerly employed in the manufacture of the finer varieties of 

 glass, hence termed ' flint glass.' 



Flints form excellent building materials ; because they give a firm hold to the mortar 

 by their irregularly rough surfaces, and resist, by their nature, every vicissitude of 

 weather. The counties of Kent, Essex, Suffolk, and Norfolk contain many substantial 

 specimens of flint-masonry. 



Formerly an important application of this siliceous substance was in the formation 

 of gun-flints, for which purpose it was cut in a peculiar manner. The following 

 characters distinguish good flint nodules from such as are less fit for being manu- 

 factured : tho best are somewhat convex, approaching to globular ; those which are 

 very irregular, knobbed, branched, and tuberose, are generally full of imperfections. 

 Good nodules seldom weigh more than twenty pounds ; when less than two they are 

 not worth the working. They should have a greasy lustre, and be particularly smooth 

 and fine grained. The colour may vary from honey-yellow to blackish brown, but it 

 should be uniform throughout the lump, and the translucency should be so great as 

 to render letters legible through a slice about ^th of an inch thick laid down upon 

 the paper. The fracture should be perfectly smooth, uniform, and slightly conchoida! ; 

 the last property being essential to tho cutting-out of perfect gun-flints. Although 

 flint locks are now but rarely employed, the process of cutting the flints to shape 

 possesses much interest. 



Four tools are employed by tho gun-flint maker. 



First, a hammer or mace of iron with a square head, from 1 to 2 pounds weight, with 

 a handle 7 or 8 inches long. Tho tool is not made of steel, because so hard a metal 

 would render the strokes too harsh, or 'dry,' as tho workmen. say, and would shatter 

 the nodules irregularly, instead of cutting them with a clean conchoidal fracture. 



Second, a hammer with two points, made of good steel well hardened, and weighing 

 from 10 to 16 ounces, with a handle 7 inches long passing through it in such a way 

 that the points of the hammer are nearer tho hand of tho workman than tho centre of 

 gravity of tho mass. 



Third, the disc hammer or roller, a small solid wheel or flat segment of a cylinder, 

 parallel to its base, only 2 inches in diameter, and not more than 12 ounces in weight. 

 It is formed of steel not hardened, and is fixed upon a handle 6 inches long, which 

 passes through a square hole in its centre. 



Foxirth, a chisel tapering and bevelled at both extremities, 7 or 8 inches long, and 2 

 inches broad, made of steel not hardened ; this is set on a block of wood, which serves 

 also for a bench to the workmen. To these four tools a file must bo added, for tho 

 purpose of restoring the edge of tho chisel from time to time. 



After selecting a good mass of flint, the workman executes the four following opera- 

 tions on it : 



