« 上一頁繼續 »
particular with regard to their sigure. The base of each cell is formed of three rhombs, as we have already said, almost always equal. According to the measurement I have made of them, each of the obtuse angles, is no degrees, and each of the two acute Ones is consequently 70. These three rhombs are inclined ,to one another, and are joined by the sides' which form one of the obtuse angles. The mutual inclination of these rhombs makes a solid angle, which on account of the general uniform equality of the thombs, is situated in the axis or centre of the cell; The six other sides of the fame rhombs, besides three obtuse angles form likewise three other angles by the reciprocal inclination, which forms their junction at the two acute angles. These six equal sides of the three rhombs are lo i; any bases oh which the bets elevate the walls which form the six sides of each cell. Each of these walls is a trapezium which has1 one acute angle of 70 degrees and an obtuse one of an hundred and ter.; the two angles of the trapezium which are at the mouth of the cell are right angles. We must observe here that the acute angle of the trapezium 'is equal to the acute angle of the rhomb at the base, and the obtuse angle of the same rhomb is equal to the obtuse angle of the trapezium. The six trapeziums which form the six sides of a cell join one another at equal sides, and are connected to the rhombs of the base; thus the obtuseanglesof therhombs are contiguous to the obtuse angles of the trapeziums, and the acute angles of these last to the acute angles of the foimer. buch is the structure of each cell.
T come new to the manner in which the two ranges of cells constituting the comb are formed, and the way in which the'cells,are joined together. Imagine to yourself in the sirst place, several other bases similar to those we have described; suppose farther, these bales to be applied to one another in sucr»
maa-< fnanner that the similar angles of the one shall correspond to the similar angles of the other, and mall join together exactly. In such a case two of these bases being joined to a third, three rhombs of these three different bases will form the bottom of a new cell similar to the first, with this only difference, that the concavity of the solid angle is turned to the other side of the comb, where there is another range of cells opposite to the first. By the junction of six bases with a seventh, there will be formed three new bases, which will have the concavity of the solid angle also turned in a contrary direction to that of the seven bases. Lastly the twelve new bates united to the eight preceding ones form nine others with the concavity of their angle opposite to that of the twelve. By this wonderful structure are formed the two ranges of combs. Thus there are three lines of rhombs on three different planes, so well executed that several thousands of rhombs of the 'ame line all red on the fame plane. Is it.not truly surprising then, that lb many thoulands of animals, aided by natural instinct: alone, mould agree together in forming a work so difficult, with lo much order and regularity?
Bees do not give their cells so determinate a structure without design. I have said that each base is formed of ti ree rhombs, and that on each side of these rhombs there is a wall which ffrves as asiJe to the opposite ceil. Those three walls, besides serving as a side to part of a cell, likewise serve for a support to the base of the opposite cell, and supply the defect arising from the great tenuity of the work. Moreover; the concavity of the solid angle which is in the middle of the base, serves by an admirable effect of divine providence to co.lect into a small ipace the panicles of honey, which the Bees daily furnish to the little larvæ, as I stiall astei wards mew. If the bottom had not been diipohul in this manner, the honey which is at sirst fluid, would have run out, and the embrio would have perished for want. It is not the sigure of the bottom only which is favourable, many advantages arise from the number of angles in the rhombs. Oq the size of them depends that of the angles, of the trapeziums which form the six sides of the cell. Now, as the acute angles of the rhombs are yoQ. 32' and the obtuse ones 1090 28' those of the trapeziums contiguous to them, must be of the same decrees respectively. Besides, by this number cf angles in the rhombs, the solid angle of the base is equal to each of the three solid angles made by the obtuse angle of the rhomb, with the two obtuse ones of the Trapeziums ; from this greatness of the angles, therefore, there results not only a greater simplicity in the work and greater facility for the Bees, who thus make use of only two' sorts of angles, but likewise greater symmetry in the disposition and sigure of the cell.
The sigure which Bees give to their cells is a regular hexagon. Pappus, a celebrated Geometrician of the second century, has observed that it looked as if these little animals had a particular acquaintance with geometry, when they gave such just proportions to their cells, Nor could they have chosen a sigure which would have afforded them a greater number of cells in the space contained in their hive. The property of this sigure is that many united together completely sill up a space round a certain point without leaving any void w hatever. The same property belongs to two other sigures, to wit, the equilateral triangle and the square. But neither of these have the capacity of the hexagon. It is theresore with great wisdom, continues the fame Geometrician, that Bees make use of that in preserence to every other sigure. For if the fame quantity of matter is employed in the construction of a triangle, a square, and a hexagon, this last \vill contain more honey than the others, "• Thj
The second example of industry and sagacity in insects shall be taken from wasps, these animals con* struct rheir nest, eiiher in the earth, or suspend it from some new building: They do not begin their fabric like Bees at the top; but like ordinary architects they lay their foundation, and raise the superstructure in the common way. The nests of all the species are not of the fame lhape. Some are ot the figure of an oblong, some of an oblate spheroid: some are conical, with the apex irregular and truncated, something like that of certain sea stiells, and. some resemble a bo; tie with a long neck. The cells in the greater number of wasp-nests are hexagonal, and surrounded externally with a white integument of a woody substance resembling the dry pods of kidney-beans; The upper part of this integument serves as a roof to the whole edifices it secures the nest from humidity, w'tiich in running along it, might incommode the wasps. The fides serve as walls to defend the inhabitants from injury; and the under part is as it were a base to the whole fabric; if the integument is removed, the inside discovers six stories at equal distances from one another. But least one mould fall and demolish those below it, each story is supported by several columns which are broad at the base, and grow broader again at the top, lo as to form a kind of arch.
The fame elegance'is slot less remarkable in the; structure of those nests which are stiaped like a bottle with a long neck. The external cover is thin, like transparent vellum. The learned Aldrovandus, having cut one of these nests longitudinally found it defended with three other integuments which like the first, were of the lhape of a bottle, but without the neck. In the centre of all these covers, he found seven hexagonal cells.
O^ a From
From the nesls of wasps I pass to the subterrraroeou J vaults of ants. These insects have a common storehouse and no ant makes any provision for its'own individual use. This storehouse is divided into several cells, the avenues to which correspond to one another. They are extended so lar within the earth, that neither rainHor, snow can reach them ki winter. The caverns of human formation are tar less artsully and skilsully contrived than those of these little animals. When they are completely sini.sh:d, any attempt to dellroy them is vain: sor their excavations are so extensive that when once the entrance is demolished, it is not possible to trace the turnings and windings of their labyrinth
The manner in which some insects form to themfelves a habitation on the leaves of plants must nor. be omitted here. 1 he tube through which they lay their eggs is at the fame time a stingwith which they puncture the leaf they mean ro lay them in. But lest the krvæ should be encumbered for want of room, they discharge a certain fluid into the hole which occasionsa tu-mour or elevation on the less, in which the young are at their ease. These tumours vary in appearance ; some are like hard shells, such as the Aleppo galls; others like little loft balls; some are scaly, others smooth, and some hairy; as to shape, some are spherical, others in the sigure of a* cone.
But it is not in the structure os' their habitations alone, that insects display their sagacity and industry; the astonishing precautions they take to secure themselves from injuries of every kind, are no less demonstrative of these qualities. Such of them as disagree with wet, avoid it with the greatest dexterity. Is wind hurtsul to any of them? the places they frequent, and the structure of their nests, sofriI ciently