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destroyed by fire, as well as to decay by age. And their places were taken by new constructions of a similar kind built on their

site. Hence, as generation after generation lived there, all kinds of articles dropped into the lakes were covered up in the silt that slowly gathered on the bottom. And now, when the lakes are drained, or when their level is lowered by prolonged drought, these accumulated droppings are laid open for the researches of

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FIG. 209.-Neolithic Implements. (a) Stone axe-head (1); (6) Barbed flint arrow-head (natural size); (c) Roughly-chipped flint celt (1); (d) Polished celt (1), with part of its original wooden hand still attached, found in a peat-bog, Cumberland; (e) Boneneedle (natural size), Swiss Lake Dwellings; a, b, c, d, reduced from Mr. Evans's "Ancient Stone Implements."

antiquaries and geologists. Many important relics of neolithic man have likewise been obtained from the floors of caverns and rock-shelters-places that from their convenience would continue to be used as in palæolithic time. Interesting evidence, also, of the successive stages of civilisation reached by early man in Europe, is supplied by the older Danish peat-bogs, in the lower parts of which remains of the Scotch fir (Pinus sylvestris), a tree that had become extinct in that country before the historic period, are associated with neolithic implements. In a higher layer of the peat, trunks of common oak are found, together with bronze implements, while in the uppermost portion, the beech-tree and iron weapons take their place.

Between the neolithic and the present period no line can be drawn. They shade insensibly into each other, and the materials from which the history of their geographical and climatal vicissitudes, their changes of fauna and flora, and their human migrations and development, form a common ground for the labours of the archæologist, the historian, and the geologist.

During the Recent period the same agencies have been and are at work as those which have been in progress during the vast succession of previous periods. In the foregoing pages we have followed in brief outline each of these great periods, and after this survey we are led back again to the world of to-day with which the first chapters of this book began. In this circle of observation no trace can anywhere be detected of a break in the continuity of the evolution through which our globe has passed. Everywhere in the rocks beneath our feet, as on the surface of the earth, we see proofs of the operations of the same laws and the working of the same processes.

Such, however, have been the disturbances of the terrestrial crust that, although undoubtedly there has been no general interruption of the Geological Record, local interruptions have almost everywhere taken place. The sea-floor of one period has been raised into the dry land of another, and again, the dry land, with its chronicles of river and lake, has been submerged beneath the sea. Each hill and ridge thus comes to possess its own special history, which it will readily reveal if questioned in the right way.

We are surrounded with monuments of the geological past. But these monuments are being slowly destroyed by the very same processes to which they owed their origin. Air, rain, frost, springs, rivers, glaciers, waves, and all the other connected agents of demolition, are ceaselessly at work wherever land rises above the sea. It is in the course of this demolition that the characteristic features of the scenery of the land are carved out. The higher and harder parts are left as mountains and hills, the softer parts are hollowed out into valleys, and the materials worn away from them are strewn over plains. And as it is now, so doubtless has it been through the long ages of geological history. Decay and renovation in never-ending cycles have followed each other since the beginning of time.

But amid these cycles there has been a marvellous upward progress of organic being. It is undoubtedly the greatest triumph of geological science to have demonstrated that the present plants and animals of the globe were not the first inhabitants of the earth, but that they have appeared only as the descendants of a vast ancestry, as the latest comers in a majestic procession which has been marching through an unknown series of ages. At the head of this procession we ourselves stand, heirs of all the progress of the past and moving forward into the future wherein progress towards something higher and nobler must still be for us, as it has been for all creation, the guiding law.

APPENDIX

THE VEGETABLE KINGDOM

I. CRYPTOGAMS OR FLOWERLESS PLANTS. 1

THESE bear spores that differ from true seeds in consisting only of one or more cells without an embryo. They include the following classes :—

Algæ-Fungi. - These embrace the smallest and simplest forms of vegetation-fresh-water confervæ, desmidiæ, mushrooms, lichens, seaweeds, etc. Some of them secrete carbonate of lime and form a stony crust, as in the case of the marine nullipores (p. 84), others secrete silica, as in the frustules of diatoms (p. 83, Fig. 31). These hard parts are most likely to occur as fossils; but impressions of some of the larger kinds of sea-weeds may be left in soft mud or sand (pp. 242, 249). Fungi are not well adapted for preservation, but traces of them have been noticed even in rocks of the Carboniferous period.

Characeæ are fresh-water plants, some of which abstract carbonate of lime from the water and deposit it as an incrustation on their surface. Hence their calcified nucules or spiral seed-like bodies [gyrogonites] and stems may accumulate at the bottom of lakes.

Muscineæ, mosses, and liverworts afford little facility for fossilisation. But some of the mosses (sphagnum, etc.) form beds of peat (p. 82). Filices, ferns, bearing fronds on which are placed the sporangia or spore-cases. Many of them possess a tough tissue which can for some time resist decomposition. Traces of ferns are consequently abundant among the fossiliferous rocks (Figs. 131, 141, 159).

Ophioglossaceæ, adder's tongues and moonworts.
Rhizocarpeæ, pepperworts.

Equisetaceæ, horse-tails, with hollow striated siliceous jointed stems or shoots (Figs. 143, 164). These stems possess considerable durability, and where buried in mud or marl may retain their forms for an indefinite period. Allied plants [Calamites, Fig. 143] have been abundantly preserved among some of the older geological formations (Old Red Sandstone, Carboniferous, Permian).

Lycopodiaceæ, club-mosses, plants with leafy branches like mosses, growing in favourable conditions into tree-like shrubs that might be mistaken for conifers. Their dichotomous stems and their fertile branches, which resemble cones and bear spore-cases, offer themselves for ready preservation as fossils. The spores are highly inflammable, and it is worthy of notice that similar spores have been detected in enormous abundance in the Carboniferous system. Lycopodium and Selaginella are familiar living genera. (For extinct forms see Fig. 142, p. 273).

1 Names placed within square brackets ([]) are fossil forms.

II. PHANEROGAMS OR FLOWERING PLANTS.

i. GYMNOSPERMS or plants with naked seeds; that is, seeds not enclosed in an ovary.

Cycadeæ, small plants resembling both palms and tree-ferns. The pinnate leaves are hard and leathery, and have been frequently preserved as fossils. Cycas and Zamia are two typical genera (Figs. 164, 171).

Coniferæ, the Pine family. The stiff hard leaves and the hard seedcones may be looked for in the fossil state (Figs. 159, 164). The resinous wood also sometimes long resists decomposition, and may be gradually petrified. Trunks of pine are often met with in peat-mosses. The Coniferæ have been subdivided into the following families :

1. Cupressineæ, cypresses, including Juniperus (Juniper), Libo-
cedrus, Thuja, Thujopsis, Cupressus, Taxodium, Glyptostrobus.
2. Abietineæ, pines and firs, including Pinus, Abies, Cedrus,
Araucaria (p. 299), Dammara, Cunninghamia, Sequoia.
3. Podocarpeæ, trees growing in New Zealand, Java, China,
Japan, etc., bearing a succulent fruit or a thick fleshy stalk.
4. Taxineæ, yews, plants with fleshy fruit, including the genera
Taxus, Salisburia, Phyllocladus.

Gnetaceæ, joint-firs, small trees or shrubs with jointed stems (Gnetum,
Ephedra, Welwitschia).

ii. ANGIOSPERMS, or plants bearing their seed within an ovary. They are subdivided into two great classes-the Monocotyledons or Endogens, and the Dicotyledons or Exogens.

Monocotyledons, so called from their having only one cotyledon or seed-lobe. They are also known as "Endogens," from the fact that they chiefly increase in diameter by growth in the interior, whereby the exterior layers are pushed outwards. Their seeds are usually enclosed in strong sheaths or shells, of which the cocoanut is a striking example. The following are some of the families :

Lemnaceæ (duck-weeds); Potamogetoneæ (pond-weeds); Pandanaceæ (screw-pines); Palmaceæ (palms); Typhaceæ (typhads, marshy plants); Cyperaceæ (sedges); Gramineæ (grasses); Juncaceæ (rushes); Liliaceæ (lilies); Irideæ (irises); Dioscoreaceæ (yams); Taccaceæ (tacca); Musaceae (plantains and bananas); Zingiberaceæ (gingerworts); Orchidee (orchids).

Dicotyledons or plants that have two cotyledons or seed-lobes; also called "Exogens," because their stems increase by successive layers added to the exterior. This division includes the most highly organised members of the vegetable kingdom. Our common flowers and hardwood trees belong to it. The sections, orders, and families into which it has been partitioned are so numerous that only some of the

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