scenery they now possess, there were long-extended saline mud-flats, thickly studded with trees now extinct, and known to the geologist by the names of Sigillaria, Lepidodendra, and Calamites. In fact, all the district now considered as "coal-yielding was then similarly circumstanced. The entire area had a geographical condition similar to the marine swamps which now fringe the coast-line of the Southern States of America. To these the slowly ebbing and flowing tides had access nearly twice a day. Around the more aged trunks of these extinct trees, standing on a muddy, shallow sea-bottom, so to speak-marine worms clustered, and their coiled tubes are now occasionally found fossilized, along with the petrified vegetation to which they clung when in life. These Spirorbi, as they are commonly termed, are tolerably plentiful in the north of England. It was owing to the semi-marine, semiterrestrial character of the area on which the luxuriant vegetation of the Carboniferous period grew, that we now find so many fossil mussels and other marine shells imbedded in the same strata. I am told that chemists have discovered only one atom of carbonic acid associated with every thousand of the other gases forming the atmosphere. The atmosphere of the period when I was born hardly contained more. This small quantity was absorbed by the waving forests into their structure, and the carbon added to their solid bulk. Day by day, and year by year, each individual tree This was before Fig. 32. grew, so that the mass of solidified carbon increased, but without exhausting the original store. This was constantly being furnished by volcanoes, as well as by the lowly animals of my own time. Everything, they say, is composed of minute parts, and originally my atoms freely floated in the air in the condition of carbonic acid. I had entered into that combination which made me part and parcel of a living tree. Once having been sucked into the leaf-pores of a Lepidodendron or Sigillaria, I started existence under a new form. I became subject to those unknown laws of vital force which philosophers find so great a difficulty in explaining. I had now an active duty to perform, and had to assist in the growth and wellbeing of the tree in whose bulk seri. I lay. But this did not prevent Bark of Sigillaria Groeme from noticing the many strange objects which surrounded me. Tree lizards, not very much larger than those which now haunt the sunny banks of old England, climbed up and down the sculptured branches of the forest trees, and lived upon the marsh flies and beetles, whose "drowsy hum" was the only sound that broke upon the stillness of the primeval woods. They found a shelter in - the hollow trunks of Sigillariæ, in association with the pupa of beetles and other insects. In some places they have been found fossilized together, a conserved recollection of those bygone times. Great reptiles, resembling frogs, in some respects, belonging to an order called Labyrinthodonta, abounded in many parts of Ireland and Scotland. In the former country was a reptile called Ophiderpeton, which had a snake-like form, and a compressed tail, so that it very much resembled a water-serpent. No fewer than five different kinds of amphibious reptiles then lived in the very country which now boasts of its freedom from these creatures! It is singular to notice how a great many of the fishes of this period had reptilian characters, whilst the first-introduced reptiles were not only the most lowly organized, but in many respects were related to fishes. Very frequently the salt-water reaches were visited by alligator-like animals, now termed Archægosaurus, whose bodies were covered by hard, horny scutes or scales, held together much after the manner a slater now adopts when he tiles a house. These reptiles were five and six feet long, and were adapted to a purely marine life. They were the principal and most powerful animals of the age I am speaking of. In one of the states of North America, Ohio, no fewer than twenty-seven species of reptiles have been found, belonging to ten different genera. Most of them are batrachians, but one has great affinities to the serpents. The atmo |