66 



AL B U R N U M A L C A. 



delete. Generic character : calyx, six sepals distinct, the 

 three lower ones are strait and connivent, swollen and 

 thicker at the points ; the three outer are spreading ; 

 stamina, six, rarely all fertile, sometimes only three 

 opposite the inferior petals bearing anthers. Style 

 triangular, terminating in three points ; capsule of 

 three places containing seeds. 



ALBURNUM is the name applied to the imper- 

 fect wood of a tree, that is, to the outermost layers 

 of wood situated immediately below the bark. It is 

 wood in a young state, having not yet acquired the 

 hardness and compact texture which characterise 

 perfect wood. It is also called sap-wood by carpen- 

 ters, because less durable than the first-formed layers 

 which are called, as well from their situation and 

 hardness, heart-wood. All kinds of timber gain so- 

 lidity and weight gradually. An oak tree, for in- 

 stance, of twenty years' growth, if cut transversely, 

 will present in the body of the wood twenty concen- 

 tric circles indicating the age of them. Of these, 

 twelve or thirteen will be dark coloured heart, and 

 seven or eight will be white coloured sap-wood. 

 Various opinions have been advanced in regard to 

 the mode in which the alburnum is formed. Some 

 suppose that it is derived from the bark, while others 

 say that both it and the bark owe their origin to a 

 peculiar fluid called cambium, formed by the descend- 

 ing sap of the plant. This fluid thickens and becomes 

 organised, giving rise each year to a layer of bark 

 and a layer of alburnum. 



ALGA The Auk. A genus of birds, belonging to 

 Cuvier's first division of web-footed birds, or those 

 which are divers. The genus has been subdivided by 

 modern ornithologists, so as to exclude the puffin and 

 some other species ; and, as it now stands, the follow- 

 ing are the leading generic characters : bill straight, 

 compressed towards the tip, tip of the upper mandible 

 hooked, that of the lower forming a salient angle. 

 Nostrils lateral, near the middle in length of the bill, 

 lineal, nearly closed by a membrane/and covered with 

 feathers, as are also the basal halves of both mandibles. 

 Feet short, placed far back, so that the birds walk up- 

 right and awkwardly. The feet, with only three toes 

 in front, completely webbed ; and acting obliquely in 

 the water, like those of the other divers. Wings short, 

 and, in some of the species, merely rudiinental, and 

 unfit for flight ; but others fly with ease, though flying 

 is not their general habit. It is, however, singular, 

 and to be regretted, that Cuvier's mistake, that " their 

 wings are decidedly too short for supporting them, 

 and they cannot fly at all," should have been allowed 

 to stand in the last edition of the Resne Animal, 

 when the first species which he mentions, the common 

 razor-bill (Alca torda) can not only fly, but fly well, is 

 a migratory bird, and builds very high on the ledges o! 

 lofty rocks. It finds its food in the sea, and during 

 the incubation, the male purveys for the female, while 

 she sits at a height of several hundred feet perpendi- 

 cularly above the water. To climb such a height, by 

 the help of the beak and feet, such feet as an auk has 

 would be difficult, if not impossible. This mistake is 

 the more singular that the species which can fly visits 

 the shores of France, and that which cannot fly does 

 not. 



The'species which can fly are not, however, air-birds 

 they never feed on the wing, neither is it their genera 

 habit to feed swimming on the surface of the water 

 They dive and feed under the water, for which their 

 forms and their feathers are equally well adapted 



During the greater part of the year they live disper- 

 sedly, scattering themselves along the shores, and to the 

 slands which are uninhabited, and at some distance 

 rom the main land. About May, they collect to their 

 >reeding places ; the wingless ones choosing the fissures 

 and holes near the water, and the winged ones the 

 edges higher up ; and when the broods are ready to 

 shift for themselves they again disperse, though some 

 are met with on different parts of the coast of Britain 

 or its isles all the year round. In winter they are 

 bund, but not very abundantly, on the flat shores of 

 .he continent, from near Calais to the entrance of the 

 Baltic ; but they do not resort thither in the breeding 

 season. From what has been mentioned of the male 

 "etching food for the female while sitting, it must be 

 obvious that the birds cannot make long journeys at 

 that time. 



These birds, as well as all the 'analogous genera, 

 lave only one brood in the season, and that consists 

 of but one individual. The egg is, however, very 

 large, and the female is a close sitter. It should seem 

 that the elaboration of a plumage, which shall fit the 

 young birds speedily for diving, requires both a large 

 egg and a careful incubation. Auks are interesting 

 birds, but they are unknown in the interior of the 

 country, and by no means familiar on the coasts, ex- 

 cept at the great nesting places of the sea-birds, and 

 these are usually the places to which there is not 

 much resort. There are two species which may be 

 briefly noticed. They are both birds of the northern 

 seas, and do not, in any longitude, range far to the 

 south. 



Common Auk. 



The Common Auk, or Razor-bill {A. torda.}, is about 

 fourteen or fifteen inches in length ; and, though the 

 closed wings do not extend further than the rump, 

 they are about two feet three inches when expanded. 

 The tail is long and wedge-shaped, or rounded at the 

 extremity, and the powers both of that and the wings 

 indicate a bird which ascends and descends readily on 

 the wing. In summer, the head, neck, and most of the 

 upper parts are black ; but there is a narrow white 

 band in front of the eyes ; the throat and upper part 

 of the breast are brownish ; and all the rest of the 

 under parts, together with the tips of the secondary 

 quills, are white. In winter the brown fades to white, 

 and the blue on the upper part becomes dull and 

 brownish. The males and females resemble each 

 other in both plumages ; and they have the bill 

 black, with a white band in the middle. The young 

 birds have the breast mottled with white ; the white 

 band across the eyes indistinct ; the bill shorter than 

 in the mature birds ; and the white band upon it is 

 wanting. It is a character of all the analogous genera 

 to have the bill shorter in proportion in the yonng 

 birds. The egg is very large for the size of the birds, 



