NAT 



[ 176 ] 



N A U 



carbonate of soda occurring massive and 

 crystallized, the principal supplies com 

 ing from lakes in Egypt and Hungary. 

 Native specimens of Natron are always 

 mixed with other salts. In Egypt, the 

 lakes which yield Natron abundantly are 

 called the lakes of Natron. These are 

 six in number, to the westward of the 

 Nile, not far from Terrana, in a valley, 

 surrounded by limestone. 

 NA'TURAL HISTORY. This extensive science 

 has for its object the enquiry into the 

 being of natural bodies, and their thorough 

 investigation in reference to their various 

 qualities, and the relative functions of 

 their component parts. Understood in 

 this extent, it presents us with a distinct 

 unique entirety, which treats the natural 

 body as complete, but gradually perfected ; 

 and at the same time seeks to discover 

 the means whereby it attained its com- 

 pletion and perfection. Natural history, 

 therefore, is no mere description of form, 

 no description of nature, as it has been, 

 latterly, very incorrectly considered, but 

 a true and pragmatical history, developed 

 from its own fundamental principles. 

 Burmeister. 



Most unjustly has natural history been 

 accused of favouring merely minute and 

 curious enquiries into the small parts of 

 creation, and of neglecting the larger 

 views and contemplations which delight 

 the man of taste and refined feeling. 

 Whoever reads the works of Pallas, Hum- 

 boldt, White, Sedgwick, or Lyell, will 

 acknowledge the error of this misrepre- 

 sentation. 



NAVICULA'RE. (from navicula, dim. of 

 navis, Lat.) The name given to one of 

 the bones of the wrist, and of the ankle. 

 NAUTILA'CEA. A family of Polythalamous 

 cephalapods, in the arrangement of La- 

 marck. This family comprises Discor- 

 bites, Nautilus, Nummilites, Polysto- 

 mella, Siderolites, and Verticialis. 

 NAU'TILITE. A fossil nautilus. 

 NAU'TILUS. A genus of shells belonging to 

 the family Nautilacea. A spiral, poly- 

 thalamous, discoidal univalve with smooth 

 sides. The turns contiguous, the outer 

 side covering the inner. The chambers 

 separated by transverse septa, which are 

 concave outwards, and perforated by a 

 tube passing through the disk. Three or 

 four recent species are known. "It is a 

 curious fact," says Prof. Buckland, "that 

 although the shells of the nautilus have 

 been familiar to naturalists, from the days 

 of Aristotle, and abound in every col- 

 lection, the only authentic account of the 

 animals inhabiting them, is that by Rum- 

 phius, in his history of Amboyna." 

 Lately Mr. R. Owen has published a 

 most admirable memoir on this subject. 



At the present day the nautilus is an in- 

 habitant of tropical seas, but its fossil 

 remains are found in formations of every 

 age. From Mr. Owen's memoir we learn, 

 that the animals by which all fossil nau- 

 tili were constructed, belong to the ex- 

 isting family of Cephalopodous molluscs, 

 allied to the common cuttle-fish. The 

 organ of locomotion in the nautilus ap- 

 pears to be a foot, resembling that of the 

 snail. This organ is expansive, and sur- 

 mounts the head. The oral organs are 

 much more complicated and numerous 

 than those of the cuttle-fish, and are fur- 

 nished with no suckers. Its tentacles are 

 retractile within four processes, each 

 pierced by twelve canals protruding an 

 equal number of these organs, so that, in 

 all, there are forty-eight. In fact, the 

 whole oral apparatus, except the mandi- 

 bles and the lip, is formed upon a plan 

 different from that of the cuttle-fish, as 

 likewise from that of the carnivorous tra- 

 chelipod molluscans, and indicate very 

 different modes of entrapping and catch- 

 ing their prey : being deprived of suck- 

 ers, they seem destitute of any powerful 

 means of prehension and detention. The 

 eye, also, is reduced to the simplest con- 

 dition that the organ of vision can as- 

 sume, without departing altogether from 

 the type of the higher classes, so that it 

 appears not far removed from that of the 

 proper molluscs. The nautilus has only 

 a single heart, the branchial one being 

 absent. The nautilus resides in the ca- 

 pacious cavity of its first, or external, 

 chamber ; and it is now well ascertained 

 that this animal is not a piratical parasite, 

 occupying the shell of another animal, 

 which it has murdered, but that it lives, 

 and sails in a skiff of its own building. 

 A siphuncle connects the body of the 

 nautilus with the air chambers, passing 

 through an aperture and short projecting 

 tube in each transverse septum, till it 

 terminates in the smallest chamber at the 

 inner extremity of the shell. These in- 

 ternal chambers contain only air, and have 

 no communication with the outer cham- 

 ber but by one small aperture in each 

 septum through which the siphuncle 

 passes. No water can by any possibility 

 pass into these chambers, between the 

 exterior of the siphuncle and the siphonic 

 apertures of the transverse plates, because 

 the entire circumference of the mantle in 

 which the siphuncle originates, is firmly 

 attached to the shell by a horny girdle, 

 impenetrable by any fluid. The number 

 of chambers varies greatly, according to 

 the age of the animal. Dr. Hook states 

 that he has found in some shells as many 

 as forty. The ascent and descent of the 

 nautilus by means of its siphuncle is very 



