X.V1TRAL HISTORY 



extraction. It is u.-ually produced on the large 

 scale by fusing its ore with a lead compound, 

 and then cupelling, or by amalgamation with 

 mercury. Silver is found in different parts of 

 the earth; but it is in the center of the Andes, 

 in situations which, though exposed to the per- 

 pendicular rays of the sun, are constantly covered 

 with snow, that nature has most abundantly dis- 

 tributed this metal. The silver-mines of Mexico. 

 Peru, and the United States, far exceed in value 

 the whole of the European and Asiatic mines. 



Snail, a term popularly applied to the mol- 

 luscous animals of the family Ilillddce, belong- 

 ing to the class Gasteropoda. The snails have 

 a well-developed, spirally-conical shell, into 

 which the animal retires at the approach of 

 winter, closing the aperture by an epiphragm 

 i which is a hardened layer of mucus). The 

 body is spiral, and distinct from the foot, 

 with a short retractile head bearing four retrac- 

 tile tentacles, on the upper pair of which the eyes 

 are carried. The mouth is armed with strong 

 horny en -cent-shaped lips, and is occupied by a 

 well-developed odontophore that is, a tongue- 

 like organ, covered with an immense number of 

 minute teeth, forming a sort of rasp. Snails lay 

 round semi-transparent eggs, which are either 

 deposited on the surface of the ground or buried 

 beneath it. The large Garden Snail is abun- 

 dant in England. This species, together with 

 some of the smaller species, has been naturalized 

 in the most remote colonies. Helix pomatia 

 is the well-known Edible Snail, or Roman Snail, 

 considered a great luxury by the ancient 

 Romans, and in the Mediterranean region is still 

 valued as an article of food, being fed in some 

 parts in large numbers in places specially 

 constructed for the purpose. 



Sparrow, a well-known bird of the finch 

 family \\hich inhabits the British Islands and 

 other parts of Europe, and has been introduced 

 into North America and Australia. Their amaz- 

 ing fecundity, their strong attachment to their 

 young, their familiarity, not to say impudence, 

 ami their voracity, are familiar to all. They 

 often do jrn.it injury in cornfields and gardens, 

 but they also do great >ervice in destroying 

 grubs, caterpillars, etc. The tree sparrow is also 

 very widely distributed. It very closely resem- 

 bles the common sparrow, but is of smaller size, 

 members of buntings are called "spar- 

 rows" in America. 



Sparrou -hau k, the common name of 

 -nc of \\lnch i- \\cll-known in 

 Britain, about twelve inches in length. The 

 male is colored dark brown on the top of the 

 head, and on the upper aspect of the body and 

 under parts are of a reddish-brown 

 color, marked \\ith narrow bands of darker tint. 

 1 he female bird is of a duller brown hue on the 

 back and head; and her plumage is diversified by 

 numerous \\hite spots. It is a bold, act r 

 very destructive to pigeons and small birds. 

 The sparrow-hawk of Australia )- marked by a 

 collar of numerous bare of \\hite. Its habits arc 



milar to thoM of the Kuropean spaiTOW- 

 l:auk. The American sparmw ha\\k i- similar 

 in si/,, to the Kuropean spartou hauk. b;;l 

 rather allied to the kestrel. It often preys en 



: kens in poultry-yards. 



Spider, the common name of insect-like 

 animals, constituting a section of the class 

 Arachnida. The head and chest are united to 

 form one segment known as a cephalothornx ; 

 no wings are developed, and breathing is effected 

 by means of pulmonary or lung sacs. The 

 abdomen is furnished with from four to six 

 cylindrical or conical mammillae or processes, 

 with fleshy extremities, which are perforated 

 with numberless small orifices for the passage of 

 silky filaments of extreme tenuity, with wnich 

 they form webs, and which proceed from inter- 

 nal reservoirs. The spiders web is usually 

 intended to entangle tneir prey (chiefly fli 

 but spiders also spin webs to make their abodes, 

 and for other purposes. The legs number four 



I pairs, and no antennae are developed. Their 

 mandibles are terminated by a movable hook, 

 flexed inferiorly, underneath which, and near 

 its extremity, is a little opening that allows a 

 passage to a Venomous fluid contained in a gland 

 of the preceding joint. After wounding their 

 prey with their hooked mandibles they inject 

 this poison into the wound, which suddenly 



j destroys the victim. The common garden or 



j cross spider, with its geometrical web, is a very 

 familiar species. The great crab spider and the 

 Surinam spider, alleged to feed on small birds, 

 are notable forms. To this family also belong 

 the trap-door spiders, which excavate a nest in 

 the ground, and fit to the aperture a curious little 

 door or lid. The tarantula is regarded in Italy 

 apable of producing a kind of dancing mad- 

 ness DV its bite. The English hunting or zebra 



i spider is a pretty little arachnidan. The Clotho 

 durundii, inhabiting Spain and North Africa, is 



; remarkable as constructing a kind of little tent, 

 in the interior of which the eggs, inclosed in little 

 pouches, are contained. The interesting water- 

 spiders, denizens of fresh- water pools, lead a 

 subaqueous life, and construct their nests some- 

 what in the form of diving-bells with the mouth 

 opening downwards, together with thin webs in 

 which their prey is captured. 



Sponge. A term properly applied to the 

 nisms which constitute the order Spongida, 

 of the sub-kingdom Protozoa, but popularly ap- 

 plied to the dead skeleton only which is sold 

 under that name. The true nature of sponges 

 has long been a matter of doubt, but they are 

 now almost universally regarded as animal . 

 They are compound bodies, and the living part 

 of the sponge appears to the naked eye as a soft 



( and gelatinous substance, which, however, is 

 seen by microscopic investigation to mnsi-t of 



Ian aggregation of extremely simple animals like 



onie of \\hich are furni.-hed with long 



cilia. This living pert ion is supported on a si. 



ton. which, in ordinary sjMuigcs. is compo-ed ot 



horny ela>tic fibers which interlace in every di- 



on. and pierced by numerous apertures, 



tinning the "s|H)nge" of commerce. 'I he 



> horny skeleton i- oompoaed of a substance called 



\kcratodc, and is usually strengthened by spicul.e 

 of lime or Hint. < >f the ap- 



I trate the sponge in every direction, some are 

 large (the i-j-lmltnt ajK-r thers are 



much smaller and more numerous (the pores, 

 '.Imhtit :i|HTturr.O. In the living sponge a 

 'ant current of \\a; li (ho- 



