Page:EB1911 - Volume 18.djvu/684

 African golden moles of the family Chrysochloridae. In a still wider sense the name is applied to the Asiatic zokors and the African strand-moles, belonging to the order Rodentia, as well as to the Australian marsupial mole.

The common mole is an animal about six inches in length, with a tail of one inch. The body is long and cylindrical, and, owing to the forward position of the front limbs, the head appears to rest between the shoulders; the muzzle is long and obtusely pointed, terminated by the nostrils, which are close together in front; the minute eye is almost hidden by the fur; the ear is without a conch, opening on a level with the surrounding skin; the fore-limbs are rather short and very muscular, terminating in broad, naked, shovel-shaped feet, the palms normally directed outwards, each with five sub-equal digits armed with strong flattened claws; the hind-feet, on the contrary, are long and narrow; and the toes are provided with slender claws. The body is densely covered with soft, erect, velvety fur—the hairs uniform in length and thickness, except on the muzzle and short tail, the former having some straight bristles on its sides, whilst the latter is clothed with longer and coarser hairs. The fur is generally black, with a more or less greyish tinge, or brownish-black, but various paler shades up to pure white have been observed.

The food of the mole consists chiefly of earthworms, in pursuit of which it forms its well-known underground excavations. The mole is one of the most voracious of mammals, and, if deprived of food, is said to succumb in from ten to twelve hours. Almost any kind of flesh is eagerly devoured by captive moles, which have been seen, as if maddened by hunger, to attack animals nearly as large as themselves, such as birds, lizards, frogs, and even snakes; toads, however, they will not touch, and no form of vegetable food attracts their notice. If two moles be confined together without food, the weaker is invariably devoured by the stronger. Moles take readily to the water—in this respect, as well as in external form, resembling their North American representatives. Bruce, writing in 1793, remarks that he saw a mole paddling towards a small island in the Loch of Clunie, 180 yds. from land, on which he noticed molehills.

The sexes come together about the second week in March, and the young—generally from four to six in number—which are brought forth in about six weeks, quickly attain their full size.

Much misconception has prevailed with regard to the structure of the mole’s “fortress,” i.e. the large breeding hillock, which is generally placed in bushes, or amid the roots of a tree; but a trustworthy account, by Mr L. E. Adams, will be found in the Memoirs of the Manchester Literary and Philosophical Society for 1903, vol. xlvii., pt. 2.

The geographical distribution of the mole exceeds that of all the other species of the genus taken together. It extends from England to japan, and from the Dovre-Fjeld Mountains in Scandinavia and the Middle Dwina region in Russia to southern Europe and the southern slopes of the Himalaya, where it occurs at an elevation of 10,000 ft. In Great Britain it is found as far north as Caithness, but in Ireland and in the Western Isles of Scotland (except Mull) it is unknown. (See ,)

 MOLECULE (from mod. Lat. molecula, the diminutive of moles, a mass), in chemistry and physics, the minutest particle of matter capable of separate existence. The word appears to have been invented during the 17th century, and remained synonymous with “atom” (Gr.  from, privative, and  , to cut) until the middle of the 19th century, when a differentiation was established. “Atom” has mainly a chemical import, being defined as the smallest particle of matter which can take part in a chemical reaction; a “molecule” is composed of atoms, generally two or more. For the detailed chemical significance of these terms, see ; and for the atomic theory of the chemist (as distinguished from the atomic or molecular theory of the physicist) see ; reference may also be made to the article.

The doctrine that matter can be divided into, or regarded as composed of, discrete particles (termed “atoms” by early writers, and “molecules” by modern ones) has at all times played an important part in metaphysics and natural science. The leading historical stages in the evolution of the modern conception of the molecular structure of matter are treated in the following passage from James Clerk Maxwell’s article in the 9th edition of the ''Ency. Brit.''

“Atom ( ) is a body which cannot be cut in two. The atomic theory is a theory of the constitution of bodies which asserts that they are made up of atoms. The opposite theory is that of the homogeneity and continuity of bodies, and asserts, at least in the case of bodies having no apparent organization, such, for instance, as water, that as we can divide a drop of water into two parts which are each of them drops of water, so we have reason to believe that these smaller drops can be divided again, and the theory goes on to assert that there is nothing in the nature of things to hinder this process of division from being repeated over and over again, times without end. This is the doctrine of the infinite divisibility of bodies, and it is in direct contradiction with the theory of atoms.

“The atomists assert that after a certain number of such divisions the parts would be no longer divisible, because each of them would be an atom. The advocates of the continuity of matter assert that the smallest conceivable body has parts, and that Whatever has parts may be divided.

“In ancient times Democritus was the founder of the atomic theory, while Anaxagoras propounded that of continuity, under the name of the doctrine of homoeomeria, or of the similarity of the parts of a body to the whole. The arguments of the atomists, and their replies to the objections of Anaxagoras, are to be found in Lucretius.

“In modern times the study of nature has brought to light many properties of bodies which appear to depend on the magnitude and motions of their ultimate constituents, and the question of the existence of atoms has once more become conspicuous among scientific inquiries.

“We shall begin by stating the opposing doctrines of atoms and of continuity. The most ancient philosophers whose speculations are known to us seem to have discussed the ideas of number and of continuous magnitude, of space and time, of matter and motion, with a native power of thought which has probably never been surpassed. Their actual knowledge, however, and their scientific experience were necessarily limited, because in their days the records of human thought were only beginning to accumulate. It is probable that the first exact. notions of quantity were founded on the consideration of number. It is by the help of numbers that concrete quantities are practically measured and calculated. Now, number is discontinuous. We pass from one number to the next per saltum. The magnitudes, on the other hand, which we meet with in geometry, are essentially continuous. The attempt to apply numerical methods to the comparison of geometrical quantities led to the doctrine of incommensurables, and to that of the infinite divisibility of space. Meanwhile, the same considerations had not been applied to time, so that in the days of Zeno of Elea time was still regarded as made up of a finite number of ‘moments,’ while space was confessed to be divisible without limit. This was the state of opinion when the celebrated arguments against the possibility of motion, of which that of Achilles and the tortoise is a specimen, were propounded by Zeno, and such, apparently, continued to be the state of opinion till Aristotle pointed out that time is divisible without limit, in precisely the same sense that space is. And the slowness of the development of scientific ideas may be estimated from the fact that Bayle does not see any force in this statement of Aristotle, but continues to admire the paradox of Zeno (Bayle’s Dictionary, art. ‘Zeno’). Thus the direction of true scientific progress was for many ages towards the recognition of the infinite divisibility of space and time.

“It was easy to attempt to apply similar arguments to matter. If matter is extended and fills space, the same mental operation by which we recognize the divisibility of space may be applied, in imagination at least, to the matter which occupies space. From this point of view the atomic doctrine might be regarded as a relic of the old numerical way of conceiving magnitude, and the opposite doctrine of the infinite divisibility of matter might appear for a time the most scientific. The atomists, on the other hand, asserted very strongly the distinction between matter and space. The atoms, they said, do not fill up the universe; there are void spaces between them. If it were not so, Lucretius tells us, there could be no motion, for the atom which gives way first must have some empty place to move into.

“The opposite school maintained then, as they have always done,