68 



COAL COAT I. 



eyes with his hands, he brought on a swelling of the 

 eyelids, so that he could scarcely open them. 



It is in this large nest that the caterpillars undergo 

 their pupa state, and indeed become winged insects. 



The other species, Bombyx pityocampa, feeds upon 

 pines and firs in the larva state, during which it is 

 less perfectly social than the preceding ; its proces- 

 sionary habits are nearly similar, but its powers of 

 annoyance are much greater. In this respect this 

 insect was known to the ancients, no less than two 

 enactments of the Roman senate prohibiting its use 

 under severe penalties (see BUPRESTID^E), being 

 accounted a deleterious poison, the hairs even occa- 

 sioning a very intense degree of pain, heat, fever, &c. 

 A single specimen of this insect is contained in the 

 British collection at the British Museum. 



COAL. The origin of this bituminous substance 

 will be traced under the general article, GEOLOGY ; 

 and we purpose confining ourselves, in the present 

 place, to a concise view of the four principal species. 

 These are brown coal, black coal, cannel coal, and 

 glance coal. 



Brown coal is imperfectly bituminous ; in all its 

 varieties it is fibrous, and in some of them its 

 vegetable origin is so complete, that the remains 

 of trunks and branches of trees are almost perfect. 

 Brown coal burns with a weak flame and disagreea- 

 ble odour. It is found in alluvial strata, and in some 

 others of comparatively recent origin : it is subdivided 

 into four varieties, viz. bituminised wood, earthy 

 brown coal, compact brown coal, and moor coal. 



Black, or slate coal, which is the foliated coal of 

 some mineralogists, is very bituminous, and is used 

 for economical purposes ; it includes several varieties. 

 It may, however, generally be said to be of a black 

 colour, having an iridescent tarnish, and a highly 

 resinous lustre. 



Cannel coal is chiefly found at Wigan, in Lanca- 

 shire, but it is more or less abundant in most collieries. 

 It is very brittle, of a shining lustre, and burns 

 quickly, leaving only three or four parts in the one 

 hundred of ashes. 



Glance coal is of a dark iron black, and has a 

 bright metallic lustre. It burns without smoke, and 

 emits no sulphureous or bituminous odour. It gene- 

 rally consists of comparatively pure carbon, with some 

 silica or alumina, and a small portion of oxide of iron. 

 There are three varieties of glance coal ; the con- 

 choidal, the columnar, and the slaty ; the last of which 

 is again subdivided into three varieties, anthracite, 

 Kilkenny coal, and Welsh culm. 



Jet or pitch coal is generally of a velvet black; it 

 occurs massive, and sometimes in the shape of 

 branches, with a regular woody structure. It has 

 a brilliant resinous lustre. It is used as fuel, but the 

 finer and harder pieces are worked into trinkets, under 

 the name of jet. 



What is called a " coal field," or district, or some- 

 times a " coal basin," may be regarded as a concavity, 

 varying greatly in extent from a few to many miles, 

 and containing numerous strata or seams of coal of vari- 

 ous degrees of thickness, alternating with sandstone and 

 clays, and soft slate or shale, containing impressions 

 of vegetables, and sometimes the remains of fresh 

 water shell-fish. The parallelism of these strata is 

 generally well preserved. The whole arrangement 

 is seldom any where quite horizontal, and never ver- 

 tical, but always more or less inclined. Beneath 

 each stratum of coal, there is often one of soft 



clay, which rarely contains the organic remains 

 of the overlying shale ; and although the alternating 

 strata of coal be very numerous, it is seldom that 

 more than three or four will afford profitable occupa- 

 tion to the miner. The upper seam is commonly 

 broken and impure ; and few beds, less than two or 

 three feet in thickness, are followed down to any 

 great depth. The depth of the mines will of course 

 vary considerably, according to the inclination of the 

 strata, the time they have been worked, and other 

 circumstances. Our deepest mines are in the counties 

 of Durham and Northumberland, and the thickest 

 beds are found in Staffordshire. 



COATI (nasua). A genus of carnivorous mam- 

 malia, belonging to the division Plantigrada, or those 

 which walk on the entire soles of the feet. They are 

 found only in America, and there are but two species, 

 the chief distinction of which is one of colour. 



Their characters are : six incisive teeth in each 

 jaw, two canines and six grinders on each side. The 

 canines are of very peculiar form. They are not 

 conical in their section, as is the case with those of 

 other carnivorous animals, but flattened externally 

 and internally, with a slight ridge on the inner sur- 

 face, and trenchant anteriorly and posteriorly, so as 

 to bear some resemblance to the teeth of the sharks, 

 only they are not serrated in their trenchant edges, 

 as the teeth of sharks are, and they have true roots 

 inserted in alveoli, in the same manner as the teeth 

 of other mammalia. They have three false grinders, 

 the first one conical in both jaws, the two following 

 ones tuberculous, and resembling those of the bears ; 

 the most striking external character, however, is that 

 of the snout, on account of which they have obtained 

 the generic name of nasua " nosey." This member 

 is very much produced, extending fully an inch iu 

 advance of the incisors in the upper jaw, and being 

 furnished with powerful muscles, resembling those 

 that give motion to the snout of a pig. There is 

 considerable difference, however, between the use of 

 the elongated snout in the pig and the coati ; and 

 there is a corresponding difference in the organisation. 

 Both snouts are adapted for digging, or routing up 

 the ground, and perhaps, for the size of the animal, 

 the snout of the coati is, in this respect, the more 

 efficient instrument of the two. But the snout of the 

 pig is the organ which guides that animal to its 

 subterranean food, and accordingly the extremity of 

 it is remarkably well furnished with nerves, being in 

 fact the most "sensitive part of the animal, and pos- 

 sessing a delicate sense of what is called touch, as 

 well as of smell, which last does not appear to be 

 very acute in the pig family. The snout of the coati, 

 on the other hand, is destitute of nerves, at least in 

 the portion which projects beyond the upper inter- 

 maxillary bone; and thus the animal has perhaps 

 less feeling in this particular organ than in any other 

 soft part of its body. In its substance it resembles 

 not a little the cartilaginous pads which are found on 

 the feet of many animals, and which, being little 

 sentient themselves, are adapted and intended to 

 protect the more sentient parts from external injuries. 

 These pads are immoveable, being mere appendages 

 to the skin, and not provided with any peculiar 

 muscles ; but the snout of the coati is not only very 

 moveable, but the animal keeps it continually in 

 motion, even when it is not used for its proper pur- 

 pose of digging ; so that one would be led to think 

 that it does so, merely to prevent the snout from 



