7. The anomalies characteristic of the western or oceanic climate increase rapidly towards its furthest limit. There is a wide difference, in respect of climate, between the Isle of Thanet and Limerick or Clare; between Norfolk and Sligo. This is clearly expressed by the changed aspect of indigenous vegetation as we go westwards towards the Atlantic. The exact registration of those differences would be the means of developing and revealing the natural laws to which the labours of the husbandman are unquestionably subject.

8. Where the constants of climate are fully ascertained, the vigorous growth of every kind of plant will be found to be restricted within limits which depend on obvious and assignable conditions, and the region suited to the cultivation of any plant may be accurately defined. Or we may reverse the process and tell the capabilities of any region.

9. But in the absence of this kind of knowledge, agriculture is necessarily founded to a great degree on imitation, without any reference to natural limits. Examples, recommended by success, are followed in situations where similar success is unattainable. Owing to the vague, indeterminate, uncollected and unarranged condition in which the data whereon the agriculturist ought to found his calculations at present lie, he must either practice empirically or imitate servilely; and he is constantly misled by examples, from want of the means of divesting them of fallacy, by estimating accurately the local element of their character. Throughout the British Isles the climate varies far more than the system of agriculture; yet the farmer may reasonably expect to find his labours more profitable the more closely his system harmonizes with nature.

10. The steady progress of scientific agriculture must be preceded by the determination of the constants of climate. The discoveries of the chemist may then be turned to account by the farmer, when we shall be able to state in a definite and authentic manner, the natural conditions of every spot of land in the kingdom.

11. The time is now come when every country must, with a view to profit, strenuously endeavour to confine itself to that kind of cultivation for which nature has especially adapted it; otherwise it must be a loser in the general and free competition. The loss of protection is the loss of an artificial and forced, and therefore, abstractedly speaking, a bad system. If this truth be understood and acted on by the farmer, the result will be an increase of production more than counterbalancing the supposed loss.

12. At the same time there has taken place an increase, in an almost miraculous degree, of the facilities of internal communication, extremely favourable to that more active system of interchange which must be expected to arise whenever agriculturists, quitting the trammels of a uniform routine, learn to take advantage of every natural capability throughout the United Kingdom. It is now no longer necessary or expedient that the farmer should be guided by the demands of the market in his own locality. The east and west can now exchange produce without delay or difficulty, and will, no doubt, frequently find their profit in so doing.

13. In setting forth the demarcations of climate within the British Islands, it would be desirable to enumerate at the same time all the useful plants and objects of culture, in different parts of the world, which seem capable of flourishing within the limits described. This kind of knowledge has a tendency to correct the spirit of routine and obstinately contracted views which render farmers at times so indocile. 14. The constants of climate, with all other physico-geographical data, and the necessary collateral information carefully and clearly arranged, so as to be easily and universally applicable, ought to be published in the cheapest possible form, and given to the people.

On the Georama. By M. GUERIN.

The author, acknowledging the invention of a Georama to be due to M. Langlard, in 1825, stated the objects he had in view in attempting to execute this great representation of the globe, and the success which he had met with.

M. Guerin had established in Paris this method of teaching geography, by portraying on a large scale the actual features of the land and sea, and offered reasons in favour of an effort to introduce the georama, and the system of instruction connected with it, in London.

ZOOLOGY AND BOTANY.

General Observations on the Geographical Distribution of the Flora of India, with Remarks on the Vegetation of its Lakes. By Prof. ROYLE, M.D. THE author stated, that though the plains of India were generally considered to support only tropical vegetation, yet this differed very much both in the different parts of the country and at different seasons of the year. The plains, moreover, might be distinguished into moist and dry; in the former, embankments were required to prevent inundation; and in the latter, canals for irrigation. In the rainy season, however, most parts supported a tropical vegetation, and rice could be successfully cultivated. So in particular localities, covered with primæval forests, some tropical plants extended even to some of the hot valleys in the neighbourhood of Cashmere. In the cold weather, however, that is in the winter season, some European plants make their appearance in the plains, especially of North-west India; and wheat and barley are as successfully cultivated as in Europe. So in ascending its mountains, especially the Himalayas, every variety of vegetation is met with, almost as much as in proceeding from the equator to the poles, being perfectly tropical at the base, European on the ascent, and polar at the summits of its lofty peaks. The mountains however are also under the influence of the rainy season, and are, indeed, for a great part of the season covered with a canopy of clouds in consequence of the air heated and loaded with moisture in the valleys rising to an elevation where the temperature is below the point of deposition or dew-point. Considerable uniformity of temperature and moisture is produced, in consequence of there being little cooling at night and but little heating during the day, from the sun being unable to penetrate the cloudy canopy, and we therefore see some of the Balsams, Scitamineæ and Orchidea flourishing at elevations where they could not exist for a day during the dry heat of summer or the piercing cold of winter.

In so extensive a territory and diversified a climate there is necessarily a numerous and a varied flora. The known species of the Indian flora are about 10,000 in number, the majority of course characteristic species, but on the Himalaya of an European type. The vegetation of the different parts of the Indian empire bears a resemblance to that of different countries where there is a similarity of climate, and about 250 species which are found in the plains and mountains of India, also occur in other, some of them very distant parts of the world. The vegetation of different tropical countries is very similar, and they are subjected to the influence of the same physical states. The affinity is very perceptible between the botany of the southern parts of India and that of the Indian Archipelago; the same thing occurs with the flora of southern China; this therefore resembles that of southern India. Mr. Brown long since remarked that about 200 species of the Australian flora are also found in the islands of the southern Pacific as well as in India. Dr. Jack observed at Singapore many remarkable points of coincidence between its productions and those of continental and western India on one hand, and the islands of the Eastern Archipelago on the other; while the prevalence of some Epacrides connected it with that of New Holland. The botany of a great part of the drier parts of India has a great resemblance to that of the west coast of Africa, as originally remarked by Mr. Brown, who ascertained that there were about 40 species common to those distant regions. Dr. Royle in the same way remarks a correspondence between the flora of Egypt and that of the drier parts of northern India, and also that some of the characteristic forms of the Mediterranean flora approach its north-western frontier.

The Himalaya mountains have a tropical vegetation at their base and in their valleys. At elevations of 6000 and 7000 feet, the climate is temperate, and the flora corresponds with that of European regions and of the Caucasus, both in its arboreous and herbaceous vegetation, and in the prevalence of many of the same species which are found here in our fields. Among them also are several genera, which, until the last few years, were thought to be peculiar to China, and others to North America.

*This communication was made to the Association at Cambridge in 1845, and was accidentally omitted in the Report for that year.

Several, indeed, of the species are identical with those found in these distant countries, separated on one hand by the cold and arid deserts of Tartary, and on the other by the hot and equally arid plains of India and of Africa, as well as the sea. Some of the peaks however, having the characteristics of polar climates, have also that of the vegetation; and it is curious to see all the families and many of the same genera on these isolated peaks and the remote Melville Island. The northern face of the Himalayas, or the Tibetan region, has the closest resemblance in its genera, and even many of its species, to that of the Atlas mountains and of Siberia, with a sprinkling of the Mediterranean flora. The author, having taken this general view, remarked on the correspondence between the vegetation of even distant countries wherever there was a correspondence in climate, and called attention to the curious resemblance in the belts of vegetation at different elevations on the Himalayas with that of different latitudes, as detailed in the author's Illustrations of Himalayan Botany.' Dr. Royle inquired with reference to some of the geological explanations of successive elevations of mountain ranges-at what period the vegetation of the peaks, for instance, came to resemble that of polar regions?

Among the various subjects, Dr. Royle stated, to which he might draw the notice of the Section, there was one, he thought, particularly worthy of the attention of those favourably situated for making observations; and that was the thick vegetation which clothes the surface of many of the lakes of India. Dr. Royle stated that he himself having been chiefly in the north of India, had not seen this vegetation to the extent in which it existed in the more southern parts of India; but even there it was sufficiently substantial to support numbers of the smaller Grallæ, and among them the Chinese Jacana. But having on one occasion been detained on the banks of some of these lakes on the north-west of Bengal, he had been much struck with the thick and varied vegetation of the floating masses with which their surfaces were covered. These consist of numerous stems, leaf and flower-stalks of a variety of plants closely interlaced and matted together, the younger parts requiring both light and air for the performance of their functions, finding their way to the surface; while the older are pushed downwards, when the more herbaceous parts rot and decay. Among these plants are most of the genera and some of the species even, which are found in similar situations in Europe; but with them such plants as Eschynomene aspera with its thick cellular stem, Convolvulus edulis, Herpestes Monniera, and Utricularia stellaris, Marsilea quadrifolia, Trapa bispinosa and bicornis, with species of Polygonum and Dysophylla verticillata. The last is particularly interesting from its long jointed and striated stem with its whorls of leaves. Of most of them it may be observed that they have little or no root; the floating stems are long and slender, very cellular, with the vascular bundles arranged round the circumference, with little or rather with nothing like bark. By Dr. Buchanan Hamilton these lakes have been seen of much greater extent, and covered with a much more dense vegetation, so much so, indeed, that he describes the floating masses to be sufficiently substantial for cattle to graze upon the grasses with which they became covered, but that occasionally some fall through and are lost. He describes, moreover, some bushes and trees as growing in the midst of the water, and among them a Rose, a Barringtonia, and a Cephalanthus.

It is hardly possible to witness such vegetation, without calling to mind some of the explanations given of the formation of coal in the ancient periods of the world, and of the indications often presented to us in coal fields of a tropical vegetation, in situations where no tropical plants could now grow. But without proceeding further, it is interesting to compare the vegetation of these lakes with that of the Indian coal-fields of Burdwan, which are in their immediate vicinity. The first thing that will strike an observer is, that there is no remarkable difference between what was the former flora of these localities, and what might take place at the present day. One great difference is certainly observable in the Indian coal-fields, and that is the immense mass of ferns of which they seem to be composed, while no ferns are at present found in their neighbourhood. This however is owing to the country and the plains of India generally being open, and therefore extremely hot and dry for some months in the year. One fern, Asplenium radiatum, is found near Delhi, in the sides of weils, in the peninsula of India, and also in Arabia. Cheilanthes dealbata and Lygodium microphyllum occur in the neighbouring Rajmuhl hills. But in the same latitude, and not very distant, where the country is covered with forests, producing

shade and moisture, numerous ferns, and even tree ferns are found, as in Silhet. The strata of the Burdwan coal-basins of Ranigunge and Chinakooree yielded the author abundant remains of the Ranigunge reed, Vertebraria indica, the marsileaceous genus, Trizygia speciosa, and species of Pecopteris, Glossopteris, &c. G. Browniana is interesting as having been found in these coal-fields, and according to Brongniart, in New Holland, in the coal of the Hawkesbury river, near Port Jackson. Zamia Buchanani has also been found, and a palm which has been called Zeugophyllites calamoites. With a little more moisture, or even the umbrageous covering of a forest, these, and other similar plants, would grow with luxuriance in these localities. Seeing therefore that heat, with moisture, is capable at the present day of supporting a vegetation similar to that of coal-fields, it would in ancient times only have required the presence of heat and moisture for the vegetation of coal-fields to have flourished. If the mass of the earth was in ancient times of a higher temperature, as is inferred from many geological and zoological phænomena, it is evident that, water being present, copious evaporation would necessarily take place as it now does in tropical countries. If the internal heat were uniform at different points of the globe's surface, then would the evaporation be uniform, and there would be an absence of those upper and lower currents of the atmosphere which now carry the heated and moisture-loaded air of the tropics to polar regions, and send the cold air of the latter towards the equator. As the air, loaded with moisture, ascended into the atmosphere, it would at length reach an elevation where the reduction of temperature would proceed beyond the point of deposition of moisture, and the whole of what had been raised by the aid of heat and air would be constantly depositing in the form of clouds and rain. Moisture would thus everywhere be preserved, and the cloudiness from the steady action of the heat below and of the cold above would necessarily also be constant. This would produce uniformity of temperature; for radiation from the surface would be obviated, and the solar rays would not penetrate the cloudy canopy more than they do in rainy weather at the present time. In such a climate, tropical plants would be able to grow equally well in any latitude, and there might be intermixed with them many others to which dryness was not essential. In conclusion, the author remarked, such a cloudy canopy may be observed to a partial extent, even in the present day. Humboldt has described it as occurring on the Andes; the author had himself observed it for days together on the Himalayas, and partially so during the whole of the rains; Dr. M'Clelland and others have described it as occurring for months together in the valley of Assam. If it existed in northern regions in early times, and the sources of heat were, as Dr. Royle assumed, internal, then could tropical vegetation not only exist in polar regions during the summer season, but it would not be destroyed in winter. Growth would only be stopped, as in the present day, during the darkness of night. As the internal heat diminished and receded from the surface, the cloudy canopy would by degrees be at a lower and a lower elevation, until, like the snow-line of the present, it would be at the surface of the earth in high latitudes. These regions would become as they are now, and immediately under the influence of external cold, and thus a glacial might succeed a tropical vegetation. In situations where a lofty peak raised itself above the canopy of clouds, it would become exposed to the cooling effects of radiation, and would, as in the present day, attract to itself and condense much of the floating moisture of the atmosphere, and give origin to mighty and rapid rivers, which would plough the mountain side and overspread the level plain.

A Synopsis of the Classification of the Genera of British Birds.
By JOHN HOGG, M.A., F.R.S., F.L.S., &c.

The author, having completed his classification of birds, which has been carried out on the same principles as that portion published in the Report of the Fourteenth Meeting of the British Association, although in some respects modified from it, gave in this communication his arrangement of the genera of the birds hitherto met with in the British Islands.

It will be seen that he has been compelled to increase the families, and that he has not inserted the subfamilies, esteeming them unnecessary, and as too much lengthening the classification. The author has been very careful in the choice of the

genera, and he trusts it will be found that he has only retained those which are really distinct; and whilst he has, after due consideration, thought it requisite to add to the number of those which British ornithologists usually employ, he has at the same time reduced those too numerous genera of certain authors, and especially of the Prince of Canino. Likewise, with regard to subgenera, the use of which the author must always maintain to be extremely disadvantageous to science, he has wholly omitted all notice of them.

*The author's Order II. Prehensores entirely consists of foreign birds, which belong to the Genus Psittacus of Linnæus. His proposed divisions of this order are given in Jameson's Edinburgh Phil. Journal for July, 1846.