and remain there ready to take it back. The French Mathematicians placed their little repeating circle at a short distance off, in a shed which the administration of marine had directed to be constructed for them. There, owing to a continuation of good weather, so little time was left for relaxation, that all the observations were finished in fifteen days; and when completed, were found to agree in a surprising manner, if the different nature of the processes be considered; and what is still more fortunate, they were found also to accord perfectly with those which M. Delambre had formerly made in the same place, at the commencement of his operations; whence results the double assurance, that the arcs of France and England are thus perfectly connected with each other; while the observations made on the other points of the two arcs, by similar processes, afford all the precision which can be desired.

As it was expedient that the point of junction of the English and French operations might always be re-ascertained, MM. Arago and Biot resolved to erect some lasting monument. The city of Dunkirk freed them from this care. A little marble column, surmounted with a spire, is to be erected in this place, and a short inscription will record the object of the operation, with the names of the observers of the two countries. the Shetland Isles, the extremity of the great arc has been marked in like manner, in the garden of Mr Edmonstone, by a little monument which he has caused to be erected in the place where the observations were made. In Spain, in the isles called Balearic, the southern extremity of the arc is consecrated by a cross.

At

These operations refer to the first of the methods by which the figure of the earth may be determined. The

other method, which employs the measure of a pendulum, had, together with the preceding, been practised on all the points of the arc. An account had last year been given, of a tour made in England, Scotland, and the Shetland Isles, to carry the apparatus of the pendulum over the whole extent of the English arc. The English government, which had favoured this operation, naturally desired that it should be executed, in like manner, by an observer of their own nation. Captain Kater, member of the Royal Society London, an experimentalist singularly exact, and author of an excellent memoir on the length of the pendulum vibrating seconds in the latitude of London, was deputed for this purpose. With much precaution, he conveyed to Edinburgh and the Shetland Islands, a solid pendulum, of an invariable form, the diurnal rate of which he had previously determined at London; and the oscillations of which he had also observed in these different places. It is the same operation which Capt. Freycinet was to execute, in his voyage round the world, with pendulums constructed under the direction of M. Arago. Capt. Kater was received at the Shetland Islands by the same Mr Edmonstone who had received M. Biot with such obliging hospitality two years before. made his observations in the same place where M. Biot did, with the same assistance and with the same accommodations. The observations of Captain Kater have been found to accord in a remarkable degree with those of M. Biot, as was ascertained by mutual comparison. Having thus the lengths of the pendulum measured by an uniform process upon the same meridian from Formentera, the most southerly of the Balearic Islands, to Unst, the most northerly of the Shetland Islands, and not only in these two islands, and in a great

He

number of intermediate points, the flatness of the earth can, by these lengths, be determined with great exactness. The amount resulting is found to be exactly the same as that derived from the lunar inequalities, or from the comparison of terrestrial de grees measured at very distant latitudes; so that all these methods, so different in their progress, so distinct in their processes, definitively terminate in this one result—the flatness of the earth; namely, the excess of the equatorial above the polar radius; the excess of the former above the latter amounting to a quantity intermediate between and The difference of these extreme values, between which the truth lies, will hardly give a hundred toises, more or less, on the half of the axis which passes through the poles of the earth; and from the number and exactness of the diversified observations by which this truth has been established, there can no longer be room for discussion on the subject.

Alexander Count Humboldt submitted to the Institute a curious paper, on the laws observed in the distribution of vegetable forms over the globe. Botany, long confined to the description of the external forms of plants, and their artificial classification, now presents several branches of study, which place it more on a foot ing with the other sciences. Such are the distribution of vegetables, according to a natural method founded upon the whole part of their structure; their physiology, which displays their internal organization; their botanical

geography, which assigns to each tribe of plants their height, limits, and climate. The terms alpine plants, plants of hot countries, plants of the seashore, are to be found in all languages, even in those of the most savage nations on the banks of the Oronoko, and prove that the attention of men has been constantly fixed on the distribution of vegetables, and on their connexion with the temperature of the air, the elevation of the soil, and the nature of the ground which they inhabit. It does not require much sagacity to observe, that on the slope of the high mountains of Armenia, vegetables of a different latitude follow each in succession, like the climates, superimposed, as it were, upon each other.

The vegetables, says M. Humboldt, which cover the vast surface of the globe, present, when we study their natural classes or families, striking differences in the distribution of their forms. On limiting them to the countries in which the number of the species is exactly known, and by divid ing this number by that of the glu. maceæ, the leguminous plants, the labiated, and the compound, we find numerical relations which form very regular series. We see certain forms become more common, from the equator towards the pole, like the ferns, the glumaceæ, the ericeæ, and the rhododendra. Other forms, on the contrary, increase from the poles towards the equator, and may be considered in our hemisphere as southern forms: such are the rubiaceæ, the malvacea, the euphorbiaceæ, the leguminous, and the composite plants. Finally, others attain their

heat into the different seasons is entirely different, and powerfully influences the phenomena of vegetation.

It has been long known, and it is one of the most interesting results derived from the geography of animals, that no quadruped, no terrestrial bird, and, as appears from the researches of M. Latreille, almost no insect, is common to the equatorial regions of the two worlds. M. Cuvier is convinced, by precise inquiries, that this rule applies even to reptiles. He has ascertained, that the true boa constrictor is peculiar to America; and that the boas of the Old Continent were pytons. Among the plants, we must distinguish between the agama and the cotyledoneae; and by considering the latter, between the monocotyledons and the dicotyledons. There is no doubt that many of the mosses and lichens are to be found at once in equinoctial America and in Europe. But the case is not the same with the vascular agama as with the agamæ of a cellular texture.

The

ferns and the lycopodiaceæ do not follow the same laws with the mosses and the lichens. The former, in particular, exhibit very few species universally to be found; and the examples cited are frequently doubtful. It is absolutely false, although it has been often affirmed, that the ridges of the Cordilleras of Peru, the climate of which has some analogy with the climate of France or Sweden, produce similar plants. The oaks, the pines, the yews, the ranunculi, the rose-trees, the alchemilla, the valerians, the stellaria, the draba of the Peruvian and Mexican Andes, have nearly the same physiognomy with the species of the same genera of North America, Siberia, or Europe. But all these alpine plants of the Cordilleras, with out excepting one among three or four thousand which we have exa

mined, differ specifically from the analogous species of the temperate zone of the Old Continent.

I.-Report on the State of Hydraulic Architecture in Great Britain; from the Work of M. Dupin, by Messrs GERARD, ARAGO, & PRONY.

Military Ports.-The arsenal at Deptford is the least considerable of all the military establishments. That at Woolwich is much more worthy of notice, as it is more spacious, and, by its position, more adapted for the construction of large vessels of war.

From 1789 to 1799, three millions and a half of francs were expended on the construction of basins, depôts, and workshops, for masts of ships only.

At Woolwich, M. Dupin observed a shed sheltered by a roof, the ironwork of which was covered with sheets of the same metal. He also describes a new forge, constructed on the plan of Mr Rennie, and on a very large scale, the bellows and hammers of which are put in motion by three steam-engines. Anchors are manufactured there, and all large pieces of iron cast and hammered which are necessary for the works of ports.

The arsenal of Sheerness offers works much more worthy of notice than those at Woolwich. Built on a swampy island formed by the conflux of the Thames and Medway, it was necessary, in the first instance, to close up a factitious ground with the carcases of old vessels sunk in the mud, side by side.

A short time since government bought the half of the town, and have taken down the houses to enlarge the arsenal. They have also built along the Medway a

magnificent quay of Cornwall granite, upon piles sunk forty-eight feet below the surface of the water.

At these works, they were busily employed when M. Dupin saw them. He describes very minutely the difficulties they had to overcome, in draining the water, driving the piles, and building under water, by means of the diving-bell. The working of this bell is effected by geometrical movements, parallel with three co ordinate rectangular axle trees, by means of iron notched roads, and wheeled notched carriages. It can be conveyed to any part under water without its being necessary to see it. Behind the new quay at Sheerness they have built depôts for masts and docks, well worthy of notice. According to the custom of the English, the masts are preserved under water. They are ranged in piles, on floors formed by beams horizontal and parallel with each other, in contiguous harbours. Double sluice gates before these harbours permit them to be full at low as well as at high water, and to be emptied at will; so that masts may be taken away or carried there. In fine, after the disposal of these masts, by separate parallel plans, you can draw away or place any piece you wish, without being forced to derange the others. The water is drained from these docks by chainpumps, put in action by a steam-engine of fifty-horse power.

Vessels may enter at high tide; but except in pressing cases, they wait until the tide is low, to drain off the water. They begin by opening the flood-gates, which allow it to escape from the docks, and then there is but very little water to pump off.

These magnificent works, executed in granite of Cornwall to be more durable, will be completed in ten years, and cost ten millions of francs. The arsenal of Chatham also pre

sents some new important hydraulic constructions. The old docks, which were in wood, are rebuilding on a very large scale in Portland stone. The old wooden docks did not close with gates on turning their hinges, but with three great wooden pannels, set at low water, and kept in their places by solid stancheons. They propose to enlarge the arsenal at Chatham very much in fact they wish to double it, by taking advantage of a spacious island formed before the old part by the conflux of the Medway. The new part they intend solely for the building of new ships, and the other for re-fitting the old ones. Thus, in spite of the colossal grandeur of the English navy, government aspire still higher; and, in the calm of peace, display more and more the essential elements of naval war.

The arsenal of Chatham contains a fine workshop of sawing, recently established by Mr Brunel. It is built on an eminence. The woods for sawing arrive by a subterraneous canal, at the bottom of a well, which empties itself near the workshop. The pieces of wood are raised by a counterpoise formed by the water proceeding from the cooler of the steam-engine, which puts the saws in motion. This water, generally lost, is at times useful. A frame, of very curious construction, carrying a double crane, put in motion by the steam-engine, the universal agent of the sawingmachine, ascends and descends upon a curved surface of 300 metres long, and takes away from, and brings back, the pieces of wood from their respective piles to the workshop for sawing. The arsenal at Chatham offers, more. over, several methods by which a great body of water is immediately conducted to any given point, to burst upon a fire.

The arsenal at Portsmouth is the