which, if not etiolated, were very deficient of greenness. This has several times occurred under a glass which cut off seventy-five per cent. of actinism, and admitted ninety-five per cent. of light. Again, behind a cobalt blue glass admitting eighty of actinism and not more than twenty per cent. of light, plants have been quite as much etiolated. It is clear, therefore, that the formation of chlorophyl is not directly dependent upon either light or actinism regarded as isolated principles.

In the greater number of my experiments with the prismatic spectrum, the greening of the plant has commenced over the space occupied by the green rays; and, under green glasses, which admitted all the rays above the orange ray, plants have invariably grown of a very green colour. The influence of the solar rays upon the green colouring matter of leaves removed by infusion and pressure, extends with tolerable uniformity over every ray of the spectrum, from the red to the violet (Sir John Herschel, 'On the Action of the Rays of the Solar Spectrum on Vegetable Colours,' Phil. Trans., vol. cxxxiii.). In this case the green colour is however destroyed, and a ruddy brown of the same character as the brown of the leaf in autumn, is produced. This change appears to be due to light rather than actinism, and presents a curious contrast to the results on inorganic compounds. Here we appear to have a deoxidation of the chlorophyl produced by light-a process analogous to the decomposition of carbonic acid by the living plant. It is difficult, however, to apply experiments made with dead vegetable matter to matter possessing the principle of life. I am led to infer from the facts, that plants will grow of a pale green colour under the influence of strong light (as admitted through yellow glass), and also under the radiations which permeate deep blue glass (actinic), whilst the heat radiations which pass glass coloured with oxide of gold, and very lightly smoked glass, have a constant tendency to produce a certain degree of ruddy brownness, even in healthy green plants; and that chlorophyl is not formed by the agency of either of those principles alone, but that it results from the combined influence of light and actinism. In every experiment made with media which cut off the heat rays, but which admit the luminous and actinic rays, the plants grow of a lively green; and the extracted green of their leaves is preserved without change much longer than under any other conditions. To produce chlorophyl, a recombination of the elements which light assists the plant to separate from the water and the air is necessary; and I have little doubt but long-continued and carefully conducted experiments will prove that chlorophyl results from the combined influences of light and actinism in exciting one of those mysterious functions of plants which excite the admiration, but elude the curiosity, of every vegetable physiologist.

I have previously stated that I have rarely succeeded in getting plants to flower under the influence of any of the media which cut off those rays usually termed the calorific rays. For instance, under intense yellow, deep blue, or very dark green glasses, however carefully the plants may have been attended to, there was seldom any evidence of the exertion of their reproductive functions. This evidently arises from the necessity of some check upon the chemical actions which depend on light and actinism, and which exhaust the elements in the formation of wood and vegetable juices which are necessary for the production of those principles which go to the preservation of the species. By removing plants when in a healthy condition from the influences of isolated light or actinism to a situation where they may be exposed to the effects of those heat radiations which are of the least refrangible class, flowers and seed are rapidly produced.

This is not an effect of heat (quoad heat), since the same temperature may

be maintained under all the circumstances, yet if the red rays are obstructed, flowers will not form. It is therefore evident that this very remarkable property must depend upon some function peculiar to this class of rays. The researches of Sir John Herschel, Dr. Draper, M. Claudet and myself on the action of the rays of the spectrum on photographic preparations, must materially assist us in explaining this phænomenon.

Sir John Herschel (Philosophical Transactions, vol. cxxxi. 1840) has shown that the red rays in some cases exalt the oxidation of a silver salt; that they exert a protective power, and even prevent the darkening of paper covered with chloride of silver under the influence of diffused light (Report of the British Association, 1839).

In the Philosophical Magazine, vol. xvi. N. S. p. 272-3, I have described several experiments, which prove not merely the protecting power of this red ray, but a power of producing the closer combination of the chemical elements of a compound exposed to its influence. More recently Dr. Draper (Philosophical Magazine, 1846), and M. Claudet, who communicated his experiments to the Meeting of the British Association at Oxford, an abstract of which appears in the present volume, have shown that this class of rays does not merely protect the chemical compound from any change, but that after the sun's rays have produced a change, they have the power of again restoring the compound to its original condition.

All these experiments have been repeated with many modifications, and particularly the influence of this class of rays on growing and dead vegetable matter has been particularly observed.

Leaves inspire carbonic acid and give out oxygen. It has been shown by Priestley, Scheele, and Ingenhousz, that flowers consume much more oxygen than any other part of the growing plant. Saussure has shown that flowers will not be developed without oxygen; that, so far from giving out oxygen when exposed to sunshine in larger quantities, as leaves do, they consume even more oxygen than before. Here we find the process which has brought the plant to this stage of growth is reversed, and in place of the decomposition which is effected by light and actinism, we have a process of reoxidation or of a close assimilation of elements, precisely analogous to that which we detect upon the Daguerreotype plate and on photographic papers under the influence of the red rays.

The results to which my experiments have led me, are—

1st. Light prevents the germination of seeds.

2nd. Actinism quickens germination.

3rd. Light acts to effect the decomposition of carbonic acid by the growing plant.

4th. Actinism and light are essential to the formation of the colouring matter of leaves.

5th. Light and actinism, independent of the calorific rays, prevent the development of the reproductive organs of plants.

6th. The heat radiations corresponding with the extreme red rays of the spectrum facilitate the flowering of plants and the perfecting of their reproductive principles.

I have been led to detect some very remarkable differences in the composition of the solar rays by frequently examining the condition of the solar radiations, according to the plan described at the commencement of this Report, for the purpose of ascertaining as nearly as possible the exact conditions in which the luminous, actinic, and calorific principles exist. During the year 1846 and the commencement of 1847, being engaged in selecting a glass for the glazing of the great Palm House in the Royal Botanic Gardens

at Kew, of which some account appears in this Volume, this examination has been more exact and continuous.

In the spring I find the actinic principle the most active, and, as compared with light and heat, in very considerable excess.

As the summer advances, the quantity of light and heat increases relatively to the actinic principle, in a very great degree.

In the autumn, light and actinism both diminish, and the calorific radiations are, relatively to them, by far the most extensive.

It should be again explained, that by light I mean to express all those rays of the spectrum which are visible to a perfectly-formed human eye; by actinic principle, the principle to which the phænomenon of chemical change under solar influence belongs; and by calorific radiations, not merely those effects which are traceable by any thermometric instruments, but also those which we can detect by the protection from change, produced by a class of rays existing near the point of maximum heat in the spectrum.

These discoveries bear most strikingly upon all my experiments; and, at the same time as they appear to confirm in a most satisfactory manner the conclusions to which my results have led me, they point to an order in the natural arrangement which is singularly interesting.

In the spring, when seeds germinate and young vegetation awakes from the repose of winter, we find an excess of that principle which imparts the required stimulus; in the summer, this exciting agent is counterbalanced by another possessing different powers, upon the exercise of which the structural formation of the plant depends; and in the autumnal season these are checked by a mysterious agency, which we can scarcely recognise as heat, although connected with thermic manifestations, upon which appears to depend the development of the flower and the perfection of the seed.

On the Facts of Earthquake Phænomena.

By ROBERT MALLET, C.E., Pres. Geol. Society of Dublin. In this Report some progress has been made; a number of authors and records of various sorts have been collated, and extracts made. Tabular forms and maps have been contrived for the more convenient classification and arrangement of the facts recorded, having regard to their import and the degree of scientific credence and value that may be attached to the statements of the various authorities.

It has been found indispensable to arrange these facts with reference to theoretic views, for the sake of perspicuity. The author trusts he will be enabled to present his Report complete to the next meeting of the British Association. Meanwhile he cannot avoid again expressing his earnest desire that the experiments upon the modulus of elasticity of rocks, &c., recommended by the Committee of Section C. at the Southampton Meeting to be made, should be proceeded with; such experiments constituting the most important of all data demanded for the further prosecution of earthquake dynamics, and the means without which the latest researches upon this subject are incapable of being tested.

Oxford, 25th June 1847.

On the Primitive Inhabitants of Scandinavia. By Professor NILSSON of Lund. Translated from the Swedish by Dr. NORTON SHAW. IN speaking of the first or aboriginal inhabitants of a country, the geological phænomena existing at the same time in that country should be taken into consideration. The question therefore, "whence the first inhabitants of Sweden came," could scarcely be correctly answered without forming beforehand a clear conception of the condition of the country at the time of its first being peopled. In a paper which a few days ago I had the honour of reading before the Geological Section "on the Rise and Sinking of Sweden," I have endeavoured to explain that the southern part of the country has from a very remote period been undergoing a gradual depression of the surface, while the northern has undergone a corresponding rise of the same; and from zoological data I have sought to prove that the southern parts of Sweden were formerly connected with Denmark and Germany. The northern parts of the Scandinavian peninsula were, on the contrary, at the same time in a great measure covered by the sea. This was probably the appearance of the country subsequent to the disturbances of nature that scattered the diluvial strata over its surface. It may be readily perceived that at a time when southern Sweden or Scania was connected with northern Germany, and the northern parts of the country were still under water, that the former, or Scania, must have received its first postdiluvian flora from the south, or from Germany. With the gradual increase of the vegetable kingdom different graminivorous animals emigrated from the south. The north being under water, these could not have come from that quarter. In the great bogs of Scania are found the skeletons of several species of these animals, which had wandered from the Germanic continent, among whom are four species of the ox-just as many of the stag-some of the wild boar, horse, and others. Carnivorous animals in search of food soon followed in the footsteps of their graminivorous predecessors; and last of all came man, to be fed by their flesh and clothed by their skins. These events seem to have occurred at a time when the Bos primigenius and Ursus spelaus existed in the country; and in proof thereof we possess in Lund a skeleton of the former pierced by an ancient arrow; and of the latter a skeleton found in a peat-bog in Scania, under a gravel or stone deposit, with implements for the chase used by the aboriginal inhabitants of the country. That the primitive inhabitants of the country stood upon the same low state of civilization as those in our days denominated savages, may be concluded from a comparison of the different implements used by them. They correspond in every respect, seem intended principally for fishing and hunting, and were formed of stone or bone. These primitive instruments are found not only in our bogs, but likewise in the ancient tumuli of the aboriginal inhabitants of the north. These tumuli are built of large, rough stones, and have always attached to them on the south or sea side, a narrow, long entrance.

We find also the skeletons of this primitive race in these barrows, and from the peculiar shape of their crania, the race may be easily distinguished from the subsequent inhabitants of Scandinavia. The skeletons of the dogs used by these beings to assist them in the chase, are likewise found. The skulls of the aboriginal inhabitants found in these ancient barrows are short (brachy-cephalic of Retzius), with prominent parietal tubers, and broad and flattened occiput. It is worthy of remark, that the same form of cranium exists among several very ancient people, such as the Iberians or Basques of the Pyrenees, the Lapps and Samoyedes, and the Pelasgi, traces of whom are still found in Greece.

Next in succession to this aboriginal race, subsisting by fishing and hunting, comes another with a cranium of a more lengthened oval form and prominent and narrow occiput. I think this second race to have been of Gothic extraction, to have first commenced the division of the land for agricultural purposes, and consequently to have had bloody strife with the former inhabitants, who, as already mentioned, lived as fishermen and hunters. This is a natural conclusion, and has been the case wherever an agricultural people has met with another living by fishing and hunting. It is the case in America, and has been so in ancient times in Europe. A strong and decided proof of the bloody struggle which had taken place between these different people is furnished by an investigation of the skull I here have the honour of showing. This skull is perforated by a lance, the point of which is formed by one of the points of the elk horn. This weapon of bone has no doubt belonged to a people very uncivilized, and probably the first inhabitants of the country, but the skull pierced by the lance is one different in form from that of the first race that peopled Scandinavia; it is on the contrary of a lengthened oval form, called by Retzius the Dolico-cephalic. This cranium was with the other bones of the skeleton found in South Scania, together with thirty to forty skeletons of the same race; and among them were found stone weapons by which they probably had been killed. Around the arms of one were seen spiral rings of bronze, which seems to prove that they had already been in contact with other people more advanced in civilization than themselves, and from them received articles of bronze. Different implements of bone or stone for digging in the ground were likewise found, and are here placed before the Section for investigation.

The third race which has inhabited Scandinavia came possibly from the north and east, and introduced bronze into the country; the form of the skull is very different from that of the two former races. It is longer than the first and broader than the second, and withal prominent at the sides. I consider this race to have been of Celtic origin. In my hand I have a skull of very similar form from the rich museum of Dr. Buckland, found in a tinmine in Cornwall, at a depth of 500 feet. Another cranium of exactly the same form, found in a hillock in Rohuslehn at a height of more than 50 feet above the surface of the sea, lies before me. In the same place was found a cranium of the preceding, or as I consider, the second race. I have another skull of like form from a so-called Phoenician catacomb in the island of Malta. (For further details upon the subject I must refer to my geological paper.) The fourth race that has inhabited Scandinavia (the true Swea race) is the colony described by Sturleson as having settled in the Malardall, and thence spreading itself in different directions, formed in Russia the dynasty of the Vareger, and in Norway that of the Norræna family, from which, during the time of Harald Haarfager, a branch extended itself to Iceland. This race it is quite certain brought with it into Sweden weapons and instruments of iron, although such may possibly have been known in the country beforehand. From the fourth race are descended the majority of the present inhabitants of the country, and with this race commences, strictly speaking, our history. The period of the first settlement of this race in Scandinavia is not so far distant as has generally been supposed, and I think may be placed some time in the sixth century.