cursed one, thus relieves the statements of the first chapter of Genesis of any attachable obscurity, and vindicates the knowledge of Him who dictated it from the aspersions of those who would fain seem to be wise above that which is written. It shews that it is possible for Moses to speak both respecting fossil species and presently subsisting ones. It shews that the writer of Genesis knew of two species at least; and the principle of degradation illustrated by one of them, taken in connection with the development of mechanical succession, and ultimate order for human existence so clearly indicated, is quite sufficient to convince any unprejudiced mind, that this portion of the Bible displays the knowledge and accuracy of Jehovah, shews us in fact, that the God of the Bible is the God of nature, for, at the period when this portion of the Bible was produced, no science of common growth could have disclosed such natural facts or principles.

In committing this lecture to the press, it is in the hope that it may be esteemed a contribution in aid of the object for which it was written. In preparing it, I have had a sincere desire to do all honour both to the works and the Word of God, and have taken advantage of every aid which the works of men afforded, or means of information or examination permitted. I have to acknowledge the kindness and courtesy of the young men's societies, Sabbath-school teachers, and missionaries, who listened to its delivery. And I hope it may help them, in some measure, to understand the mechanics of the Bible, and to appreciate that wondrous book, which, while it sheds light on the darkness of primeval ages, brings life and immortality to light, and dispels the darkness of the grave and the future world.

GEOGRAPHICAL BOTANY.

BY JAMES C. NIVEN, ESQ.,

Curator of the Hull Botanical Gardens, and Lecturer on Botany to the Hull School of Medicine.

[Delivered before the Royal Institution, Hull.]

THE Geography of Plants, or "Phytogeography," as this branch of botanical science is termed, is a study of modern origin, with which the name of the illustrious Baron Von Humboldt is intimately associated. In him, this science found a noble architect. Naturally endowed with abilities of the highest stamp, and possessed of physical energies correspondingly vigorous, with ample means at his disposal, he, early in life, bade adieu to his native shore, and with a soul thirsting for a more intimate knowledge of nature, we find him at one time penetrating the recesses of the primeval forests of South America, at another, contemplating the majestic landscape from the summit of the Andes, or wandering over the wild steppes of Tartary, and, studying the various phenomena of nature under all circumstances, with a mind well trained for scientific observation. What must be the feelings of such a man, when, at an age far advanced beyond the allotted "three score years and ten," he surveys his past career from the highest pinnacle of scientific knowledge, and with a mind capable of grasping the universe, he transmits to posterity his "Cosmos," a history which, in the words of Meyen, "may be said to embrace all sciences, and to place before the mind's eye of the reader a pic

B

ture, whose limits extend from the remote nebulæ of the celestial sphere to the internal organisation of the crust of our earth."

Heat, light, and moisture are the great supporters of vegetable life. From the relative position of the earth and the sun the heat would, but for various medifying causes, be greatest at the equator, and gradually lessen towards the poles. What are these modifying causes? You know that there is more water than land on the surface of the earth, and as solid substances absorb and radiate heat much better than liquids, it follows that those countries which are distant from the sea are subject to greater extremes of temperature than those bordering the sea, because the sea moderates the winter's cold, and also tempers the summer's heat. Again, we find that there are particular currents of air, or "trade winds," and associated with them currents of water, in the great oceans of both the northern and southern hemispheres; in the former these blow from the north-east, and in the latter from the south-east, towards the equator. The current of air that rises in the north-east has not a very definite course till it reaches the 30th parallel of latitude, when it becomes known as one of the trade winds; in its onward progress it carries along with it a strong oceanic current; this meeting at the equator the opposing currents resulting from the southern trade winds, takes a westerly direction, till it strikes the coast of South America, along which it proceeds northwards, passing through the Gulf of Mexico, whence it derives its name of "the gulf stream." It then takes a north-east course, striking on the shores of Great Britain and Norway, and moderating the temperature even as far north as Spitzbergen, a considerable way within the arctic circle. The mild climate and verdure of this country are mainly due to the influence of the gulf stream. From a similar cause, the north-eastern shore of the American continent enjoys a much milder climate than the north-western.

Heat alone will not support vegetable life; there must be moisture. The vast deserts of Africa possess the extreme of heat, but, lacking moisture, they are almost devoid of vegetation; so are parts of Arabia and Persia, and the vast table lands of La Plata, Mexico, and Thibet. On the other hand, the Brazils, with equal heat, enjoy, from their rain-attracting mountains, profuse verdure. Humboldt endeavoured to ascertain the laws of geographical temperature, and originated a system of lines of heat and cold for all places having reliable data; the lines marking places of equal mean summer temperature, he called "isotherms;" and the lines denoting a similar mean depression of winter temperature, he called "isochimenals."

Vegetation is very much affected by the chemical nature of the soil. Certain plants will flourish only in peculiar soils, and a botanist can determine the geological character of a locality with tolerable accuracy, from studying its flora. This difference of vegetation is perhaps nowhere more distinctly marked than in our own bogs; they extend over vast tracts of country, with no variation, unless such as may be induced by the presence or absence of water, or by the different stages of decomposition the soil has attained. In those localities where the chalk formation approaches the surface, we have another very marked instance of this, which may be illustrated by a day's botanical ramble among the hills in this neighbourhood, where you will find wild flowers in abundance, such as you will not gather elsewhere in the whole district of Holderness. The sea side has its peculiar plants also. Few of our littoral plants occur at any great distance from the shore, unless it be on the salt steppes of both the Old and New World, where the very fact of their occurrence tends to confirm the conclusion, that these steppes, at an earlier period of our earth's history, formed extensive inland seas. Added to this, the mechanical texture of the soil must not be overlooked, as on it

depends to a considerable extent the natural drainage, and the consequent variation of terrestrial temperature,points of material importance.

With an increase of latitude there is a proportionate decrease in the number of species of plants, as well as in the number of individuals of each species, and at the same time the proportion of the lower to higher forms of the vegetable kingdom increases as you recede from the equator. The same is equally true of altitude. Take, for instance, a mountain within the equatorial region, and we find that its flora is a perfect miniature of the general surface of our earth.

There have been several systems advanced, with a view to the phytogeographical division of our globe. The systems proposed by Professors Schow and De Candolle, and that by Humboldt, are the most important. The system advocated by the first named botanists rests altogether on statistical data, the earth's surface being divided into certain districts or kingdoms, according to a numerical analaysis of the flora of a locality. In some few instances these kingdoms are well defined; but the reverse is much more frequently the case, especially in our northern latitudes, where the natural groups are so intermingled. A more serious objection to this system consists in the fact that, before such a division can take place, we must possess a perfect acquaintance with the flora of the whole world. Humboldt, knowing that such a statistical division was impossible with our present limited knowledge, and, even if it were, that its value could only be appreciated by the few who had made the science of botany a study, based his system on the outward appearance of nature, and divided the earth into regions by lines running more or less parallel to the equator, so that all the countries lying within those lines present a general similarity in floral appearance. If it be objected that this system is not sufficiently definite for scientific purposes, it has the great advantage of being easily