ON THE GENERAL DIFFUSION OF KNOWLEDGE. 



soir salt, &c. The class of inflammable sub 

 stances comprehends sulphur, carbon, bitumen, 

 coal, amber, cnarcoal, naphtha, petroleum, as 

 phalt, caoutchouc, mineral tar, &c. The metallic 

 class comprehends plaiina, gold, silver, mercury, 

 ooppur, iron, lead, tin, bismuth, zinc, antimony, 

 cobalt, nickel, manganese, molybdenum, arsenic, 

 scheele, menachamte, man, silvan chromium, 

 tungsten, uranium, titanium, tellurium, sodium, 

 potassium, &c. All these mineral substances 

 are distinguished by many varieties of species. 

 There are eiglit genera of earthy fossils. One 

 of these genera, the flint, contains 34 species, 

 besides numerous varieties, such as chrysobe- 

 ryls, topazes, agates, beryls, quartz, emery, 

 diamond spar, &c. Another genus, the clay, 

 contains 32 species, such as opal, pitch-stone, 

 felspar, black chalk, mica, hornblende, &c. and 

 another, the calc, contains 20 species, as lime 

 stone, chalk, slate, spar, fluor, marie, boracite, 

 loam, &c. There are ten species of silver, five 

 of mercury, seventeen of copper, fourteen of iron, 

 ten of lead, six of antimony, three ofbismuth, &c. 

 All the bodies of the mineral kingdom differ from 

 one another as to figure, transparency, hardness, 

 lustre, ductility, texture, structure, feel, sound, 

 smell, taste, gravity, and their magnetical and 

 electrical properties ; and they exhibit almost 

 every variety of colour. Some of those sub 

 stances are soft and pulverable, and serve as a 

 bed for ihe nourishment of vegetables, as black 

 earth, chalk, clay, and marl. Some are solid, 

 as lead and iron ; and some are fluid, as mer 

 cury, sodium, and potassium. Some are brittle, 

 as antimony and bismuth, and some are mallea 

 ble, as silver and tin. Some are subject to the 

 attraction of the magnet, others are conductors 

 of the electric fire; some are easily fusible by 

 heat, others will resist the strongest heat of our 

 common fires. Some are extremely ductile, as 

 olatina, the heaviest of the metals, which has 

 been drawn into wires less than the two thou 

 sandth part of an inch in diameter, and gold, 

 the parts of which are are so fine and expansi 

 ble, that an ounce of it is sufficient to gild a sil- 

 ?er wire more than 1300 miles long. 



In order to acquire the most impressive idea 

 of the mineral kingdom, we must visit an exten 

 sive mineralogical museum, where the spectator 

 will be astonished both at the beauty and the 

 infinite diversity which the Creator has exhibit 

 ed in this department of nature. Here it may 

 be also noticed, that not only the external aspect 

 of minerals, but also the interior configuration of 

 many of them, displays innumerable beauties 

 and varieties. A rough dark-looking pebble, 

 which to an incurious eye appears only like a 

 fragment of common rock, when cut asunder and 

 polished, presents an assemblage of the finest 

 veins and most brilliant colours. If we go into 

 a lapidary s shop and take a leisurely survey of 

 is jaspers, topazes, cornelians, agates, garnets, 



and other stones, we cannot fail to be struck whh 

 admiration, not only at the exquisite polish and 

 the delicate wavings which their surfaces pro 

 sent, but at the variety of design and colouring 

 exhibited even by individuals of the same spe 

 cies, the latent beauties and diversities of which 

 require the assistance of a microscope to dis 

 cern, and are beyond the efforts of the most ex 

 quisite pencil fully to imitate. 



Not only in the objects which are visible to 

 the unassisted eye, but also in those which fan 

 only be perceived by the help of microscopes, is the 

 characteristic of variety to be seen. In the 

 scales of fishes, for example, we perceive an in 

 finite number of diversified specimens of the 

 most curious workmanship. Some of these are 

 of a longish form, some round, some triangular, 

 some square ; in short, of all imaginable variety 

 of shapes. Some are armed with sharp prickles, 

 as in the perch and sole ; some have smooth 

 edges, as in the tench and cod-fish ; and even 

 in the same fish there is a considerable variety ; 

 for the scales taken from the belly, the back, the 

 sides, the head and other parts, are all different 

 from each other. In the scale of a perch we 

 perceive one piece of delicate mechanism, in the 

 scale of a haddock another, and in the scale of 

 a sole, beauties different from both. We find 

 some of them ornamented with a prodigious 

 number of concentric flutings, too near each 

 other and too fine to be easily enumerated. 

 These flutings are frequently traversed by others 

 diverging from the centre of the scale, and pro 

 ceeding from thence in a straight line to the cir 

 cumference. On every fish there are many thou 

 sands of these variegated pieces of mechanism. 

 The hairs on the bodies of all animals are found, 

 by the microscope, to be composed of a number 

 of extremely minute tubes, each of which has a 

 round bulbous root, by which it imbibes its pro 

 per nourishment from the adjacent humours, and 

 these are all different in different animals. Hairs 

 taken from the head, the eye-brows, the nostrils, 

 the beard, the hand, and other parts of the body, 

 are unlike to each other, both in the construc 

 tion of the roots and the hairs themselves, and 

 appear as varied as plants of the same genus but 

 of different species. The parts of which the 

 feathers of birds are composed, afford a beauti 

 ful variety of the most exquisite workmanship. 

 There is scarcely a feather but contains a mil 

 lion of distinct parts, every one of them regularly 

 shaped. In a small fibre of a goose-quill, more 

 than 1200 downy branches or small leaves have 

 been counted on each side, and each appeared 

 divided into 16 or 18 small joints. A small part 

 of the feather of a peacock, one-thirtieth of an 

 inch in length, appears no less beautiful than the 

 whole feather does to the naked eye, exhibiting 

 a multitude of bright shining parts, reflecting first 

 one colour and then another in the most vivid 

 manner. The wings of all kind of insects, too. 



