FUNCTIONS OF BIRDS. 15 



altogether carnivorous ; others, as many of the web-footed tribes, live on fish ; eomo 

 on insects and worms, and many on fruits or grain. The extraordinary powers of 

 the gizzard in the graminivorous tribes, in comminuting their hard food, so as to pro- 

 pare it for digestion, are such as almost to exceed credibility. In order to ascertain 

 the strength of these stomachs, the Abbe Spallanzani made many cruel, though at 

 the same time curious and not uninteresting experiments. Tin tubes full of grain 

 were forced into the stomachs of Turkeys ; and, after remaining twenty hours, were 

 found to be broken, compressed, and distorted in a most irregular manner. The 

 stomach of a Cock, in the space of twenty-four hours, broke off the angles of a 

 piece of rough, jagged glass ; and, on examining the gizzard, no wound or laceration 

 appeared, Twelve strong tin needles were firmly fixed into a ball of lead, with their 

 points projecting about a quarter of an inch from the surface ; thus armed, it was 

 covered with a case of paper, and forced down the throat of a Turkey. The bird 

 retained it a day and a half without exhibiting the least symptom of uneasiness. 

 When the Turkey was killed, the points of nearly all the needles were found to be 

 broken off close to the surface of the ball Twelve small lancets, very sharp both 

 at the points and edges, were fixed in a similar ball of lead. These were given in 

 the same manner, to a Turkey-cock, and left eight hours in the stomach ; at the 

 expiration of which time that organ was opened, but nothing appeared except the 

 naked ball ; the twelve lancets having been all broken to pieces. From these facts 

 it was concluded, that the stbnes so often found in the stomachs of many of the 

 feathered tribes, are highly useful in assisting the gastric juices to grind down the 

 grain and other hard substances which constitute their food. The stones themselves, 

 also, being ground down and separated by the powerful action of the gizzard, are 

 mixed with the food, and no doubt contribute to the health as well as to the nutri- 

 ment of the animals. 



All birds are oviparous, or produce eggs, from which, after the process of incuba- 

 tion, the young are extruded. These eggs differ in the different species, in number, 

 figure, and color. They contain the rudiments of the future offspring ; for the 

 maturation and bringing to perfection of which, in the incubation, there is a bubble 

 of air at the large end, betwixt the shell and the inside skin. It is supposed that, from 

 the warmth communicated by the sitting bird to this confined air, its spring is in- 

 creased beyond its natural tenor, and, afthe same time, its parts are put into motion 

 by the gentle rarefaction. Hence pressure and motion are communicated to the 

 parts of the egg ; and these, in some unknown manner, gradually promote the for- 

 mation and growth of the young one, till the appointed time of its exclusion. The 

 use of that part of the egg called the treddle, is not only to retain the different 

 liquids in their proper places, but also to keep the same part of the yolk uppermost ; 

 which it will effectually do, though the egg be turned nearly every way. The 

 mechanism seems to be this : the treddle is specifically lighter than the white in 

 which it swims ; and being connected with the membranes of the yolk, at a point 

 somewhat out of the direction of its axis, this causes one side to become heavier 

 than the other. Thus the yolk, being made buoyant in the midst of the white, is, 

 by its own heavy side, kept with the same part always uppermost. 



The nests of birds are, in general, constructed with astonishing art ; and with a 

 degree of architectural skill and propriety, that would foil all the boasted talents of 

 man to imitate. 



'Mark it well, within, without : 

 No tool had he that wrought ; no knife to cut, 

 No nail to fix, no bodkin to insert, 

 No glue to join ; his little beak was all. 

 And yet, how neatly finish'd ! What nice hand, 

 With every implement and means of art, 

 And twenty years' apprenticeship to boot, 

 Could make me such another ? Fondly then 

 We boast of excellence, whose noblest skill 

 Instinctive genius foils. 



In most of the species both the male and female assist in this interesting operation. 

 They each bring materials to the place : first sticks, moss, or straws, for the founda- 

 tion and exterior : then hair, wool, or the down of animals or plants, to form a soft 

 and commodious bed for the eggs, and for the bodies of their tender young, when 

 batched. The outsides of the nests bear in general so great a resemblance in coloi 



