« VorigeDoorgaan »
Recent Account of the African Desert | to west, necessarily lay bare the eastern Sahara.
portion. Hence arises that great quan
tity of rolled pebbles, of naked rocks, The extent, nature, formation, and en- and of denuded oases, which are found croachments of this mighty desert have in the Sahara, or eastern district; while lately been more accurately defined than the moving sands of the western one, heretofore by Ritter, in his Géographie (the Sahel) advance gradually towards Comparée. It is bounded on the north the ocean, and are formed on its shores by the Biled ulgerid (the Country of into sandy downs by the effect of the Dates); to the east it reaches the At- great rotatory movement of the Atlantic lantic; towards the south it stretches, Ocean. very uniformly, to the Senegal and the
Excellent springs, wells, marshes Niger, with which rivers it extends and lakes, are met with in the Sahara, between the 169 and 18° of north lati- on the sides of the ranges of rocks, espetude, into the unknown regions of east- cially in Winter: but all these advanern Soudan. In magnitude, the Sahara | tages disappear in the Sahel, where may be compared to the half of Europe, nature presents no variety. Rivers, or still more definitely to about double springs, oases, wells, and saline lakes, the Mediterranean; the area of the desert are there nearly unknown. Nothing is being 72,000 geographical square miles, seen but indurated rock-salt, and moving including the Oases, and to 50,000 sand: water is only to be met with by square miles without them: its length digging to an enormous depth, even is 450, and its width 300 geographical where the process is at all practicable; miles.
while the few wells which are dispersed The essential characteristic of this over the interior, are so deep that the desert consists in its uniformity both of caravans can derive no advantage from surface and substance; the dead level them. To prevent their being choked of the former is only varied by compara- with sand, the wells which have been tively slight elevations and depressions, successfully established are walled round
a feature which precludes the accu- with bones of camels for want of stones, mulation of large bodies of water, and covered over with skins: the skili while the latter, generally speaking, is with which the conductors of caravans a mass of pebbles, or salt, equally dis- trace their way in these monotonous solitributed. The limestone, which rises tudes to these wells when once known, into the elevations in the neighbourhood is admirable. of Fezzan, and in the Haroush, is, ac- The prevailing winds in the Libyan cording to Humboldt, of a formation desert are from the north and northanalogous to that of the Jura: in Dar- east; the consequence is that hills of four it occasionally encloses granite, talc, sand are continually advancing from and basalt. The rocks are covered over those quarters, at the usual rate of ten with pebbles, shingle, and with moving or twelve feet, as has been estimated by sand, which the wind raises in clouds like the gradual disappearance of springs to a fine fog. The sand of the Libyan and wells: these winds only raise into desert is composed of transparent frag- the air the fine sand;—the pebbles and ments of quartz, about the third of a shingle remain bare. The moving desert line in diameter; with this the surface consequently covers with its sands those of the subjacent rock is equally covered spaces which it has gained, while the over in a manner analogous to that with wind from the district of moving sands which snow would be deposited. converts it into a plain of gravel, pebbles,
The eastern portion of this vast desert and shingle. The portion designated is much freer from sand than the west- as Sahel, thus forming the advance ern; it is intersected by low rocky guard of the Sahara, in time becomes shelves, denuded of sand, and quite converted into the latter; but this phebarren, and it contains a great num- nomenon is not general in Libya. The ber of oases. The western part, on the progressive advance of the sand does contrary, is nearly destitute of the lat- not then leave behind it, as might be ter; and the few that are met with expected, vast naked plains, because the are very limited in extent. The terrific Mediterranean is ceaselessly throwing hurricanes, which about the period of up considerable masses of sand on its the equinoxes, annually sweep over this shores, these the winds seize hold of, sandy ocean, being directed from east and carry towards the interior of the con
tinent: this process may be detected by Huttonian Theory of Rain Conthe gradual disappearance of the palm
troverted. trees under the sand along the coast. The sea has even, in many places, The most plausible Theory of Rain enabled the Libyan desert to extend its ever given to the world, is that of Dr. domain at the expense of the valley of Hutton. He supposes two currents of the Nile. This encroachment is espe- air of different temperatures, both nearly cially remarkable near to the village of saturated with vapour, to be mingled Warden, at the northern extremity of together, and that a precipitation of the plain of Gizeh. A belief in this course takes place, in accordance with encroachment of the sands is general the known fact, that at their mean temamong the Arabs, who possess accurate perature all their vapour cannot be reknowledge of all the phenomena of the tained, and therefore the surplus will be desert. The well-known colossal sphinx precipitated. This theory is defective which is now half buried by the sand, in two respects : First, it does not show appears to them a talisman, incessantly how two currents of air could be mingled conjuring the storm of sand not to to any considerable extent; and second, advance further. Caviglia, who under- it does not show by calculation, that took to excavate the hillocks of sand rain to any considerable amount would accumulated at its base, discovered be produced, even if large masses of air, many remarkable objects which the at very different temperatures, should desert had ingulfed.
be mingled together, which it would be The same effects from the sand are easy to show never can happen, espeperceivable in Nubia, whereof the nu- cially in the torrid zone. It may fairly merous sphinxes, forming the avenue be presumed that no advocate of the leading to the propylæum of the temple Huttorian theory would suppose that of Sibhoi, six alone are now visible: all more than five hundred feet of a stratum the others, together with the greater of cold air could be mingled with a part of this superb temple, being over- stratum of warm air, five hundred feet whelmed by sand.
of perpendicular height. Now it will An account of a recent personal visit be found by calculation, that if one of to the Sahara is about to issue from the these strata is at 60°, and the other at French press at Algiers. M. Baudoin, 40°, and both saturated previous to their a native of Provence, being at Algiers mixture, the whole amount of precipitasoon after the taking of the city by the tion, provided they took the mean temFrench, was surprised, as he was walk- perature of 50°, would be less than a ing in the environs, by a party of Arabs grain and one half on each square inch of the Issers tribe, and carried off by of surface. But as the latent caloric them into their own territory; there evolved in the condensation of the they circumcised and sold him to a vapour, would not suffer the mean temMahometan priest. A long series of perature of the two strata, when mixed, travels and singular adventures followed to be acquired, but some temperature this event, and with his master he above 50°, therefore a less quantity than reached the Sahara. During his journey, that mentioned would be precipitated. he describes having seen some wealthy Such a quantity, in most cases, would cities and interesting ruins; among the be entirely evaporated in passing down latter he saw inscriptions, whose cha- through the air below, and never reach racters resembled neither the Greek, the earth. nor Latin, nor Arabic alphabets. Having It was mentioned before, that 5:1 obtained his liberty by the death of his inches of rain fell in Wilmington, on master, who fell a victim to the cholera, the 29th of July, 1834, in two and a which raged to the very centre of Africa half hours ; let us see whether such a in 1835, he immediately prepared to rain could be produced at all, on the rejoin his compatriots, and succeeded Huttonian principles, making the most by avoiding the direct routes. The extravagant allowance for the quantity narrative, by a competent person, of of air mingled, and also for the differa journey made under such circum- ence of temperature of the two strata. stances, would be extremely valuable, Let us suppose, then, that one-half as the part of Africa said to have been of the atmosphere at 80° Fahr., should visited" is scarcely known to Euro- be mingled with the other half at zero peans.
over the region round Wilmington,
that 5'1 inches of rain is 'the result. This refutes the hypothesis of rapid What will be the temperature of the permeation of air by vapour, and, inmingled mass after the rain ? The deed, proves that vapour, like heat, mean temperature is 40°, which would when it passes up to the upper regions, be the temperature after the mixture, if must be carried by the air, and not no latent caloric is given out in the con- thrust up by its own elasticity. But to densation of vapour.
But from the return from this digression; if the principles explained before, it will be Huttonian theory is unable to produce found, that as five inches of rain is such a rain as that at Wilmington, aốo of the whole atmosphere in weight, what will it do with the one which the latent caloric given out in the con- occurred at Geneva, on the 25th of densation of the vapour forming this October, 1822, when it rained thirty rain, will be sufficient to heat the whole inches in twenty-four hours; or the one compound 59-7°, which being added to at Joyeuse, on the 9th of October, 1827, the mean temperature 40°, will make when it rained thirty-one inches in the temperature of the air after the twenty-two hours *? rain 99.7°, almost 20° hotter than the Or how will it account for a storm of hottest half of the atmosphere before hailt which fell in Orkney on the 24th the mixture.
of July, 1818, in the afternoon, nine Having found that the Huttonian inches deep in less than nine minutes ? theory would not bear the test of calcu- -Espy, ° Franklin Journal, August, lation, I imagined there was but one 1836. other possible mode of condensing vapour, and that was that the vapour by its Recent Meeting of German Natuown elasticity in the lower parts of the
ralists, fc. atmosphere, thrust itself up into a cold The annual meeting of the naturalists stratum above, whenever such a one and medical men of Germany, comoverlapped the one below, and was thus menced at Jena, in the Duchy of Saxecondensed into rain.
Weimar, on the 20th ult., and termiThis hypothesis, I thought, was alto- nated on the 26th, Dr. Kieser, President. gether reasonable, from the great dis- The number of members was large. covery of Dalton and Gay Lussac, that From countries foreign to Germany, vapour in the atmosphere rests only on there were more from Great Britain vapour, and thus forms an independent than any other. France did not appear atmosphere, and is not supported in the to have had one. Among the British least degree by the air. I imagined, visiters, were Professors Daubeny (Oxthen, that vapour could rush with great ford,) (distinguished so recently for the velocity from air where the dew-point effective discharge of his duties as one was high, to air where the dew point of the secretaries of the British Assowas low. But when I discovered that ciation at Bristol,)-Graham (Glasgow,) some rains were so great as to be beyond and-Kane (Dublin.) The Grand Duke the power of this theory, too, I began to of Saxe-Weimar and his court were suspect the hypothesis itself, which in- present, and paid the most marked duced me to put it to the following trial. respect to the objects and members of
I united two glass retorts together by the Association. The Duke of Saxetheir necks, then having covered one Altenburg founded a premium in Nawith snow, I put ten drops of water into tural Philosophy, for the students of the
I the other, and placed it in a vessel of University of Jena, as a token of the water at the temperature of 130°, letting interest he felt in the Association. The it remain in that situation seven hours, meeting for 1837 is to be held at the temperature of the room during the Prague. It was stated that the number experiment being about 70°; not one
of members at Bonn, in 1835, was drop was distilled over in all that time.
about five hundred. I then took the retorts apart, leaving open the neck of the one having the Freiburg Suspension Bridge. water in it; it has continued in the room, When the details of the construction open now for thirty days, with a tempe of this extraordinary attempt, to sur'rature of 70° night and day, and the dew-point in the room never as high as * Edinburgh Transactions, 1823. 40°, the ten drops of water being now + POUILLET Elemens de Physique, II. only slightly diminished.
pass, in span*, every other bridge which certain legislative enactments, providhad preceded it, were examined in Eng. ing that Coal in London should be sold, land, considerable doubts were enter- and the duty upon it be rated, by tained, as to the soundness of the prin- measure, and not by weight. The ciples which had directed some parts smaller coal is broken, the greater the of the arrangements, particularly in that space it fills; it became, therefore, the where the engineer had made an angle interest of every dealer in Coal, to buy in the direction of the land-chains, and it of as large a size, and to sell it of as thus deposited a part of the pull upon the small a size as he was able. This comrock, &c., where the angle takes place, pelled the proprietors of the Coal-mines instead of carrying the whole pull along to send the large Coal only to market, one continued line, to the point of and to consign the small Coal to deattachment at the extremities of the struction. chains, as in Menai-Strait Bridge. In the year 1830, the attention of
From this, or from other, cause have parliament was called to these evils; arisen, we regret to say, some appear- and pursuant to the Report of a Comances of insecurity, and early in this mittee, the duty on Coal was repealed, year the authorities of Freiburg tem- and Coal directed to be sold by weight porarily prohibited the transport of instead of measure. The effect of this heavy loads it. We shall rejoice change has been, that a considerable to hear that this injunction is removed. quantity of Coal is now shipped for the
London market, in the state in which it Wanton Destruction annually of a
comes from the pit; that after landing Million Chaldrons of Coal.
the cargo, the small coal is separated by
screening from the rest, and answers as As there is no reproduction of Coal in well as much of the Coal which was
fuel for various ordinary purposes, as this country, since no natural causes are sold in London before the alteration of now in operation to form other beds of
the law. it; whilst, owing to the regular increase
The destruction of Coals on the fiery of our population, and the new purposes heaps near Newcastle, although dito which the steam-engine is continu
mi ed, still goes on, however, to a ally applied, its consumption is advancing at a rapidly accelerating rate ; it is frightful extent, that ought not to be
permitted ; since the inevitable conseof most portentous interest to a nation, that has so large a portion of its inhabit quence of this practice, if allowed to
continue, must be, in no long space of ants dependent for existence on ma- time, to consume all the beds nearest to chinery, kept in action only by the use the surface, and readiest of access to the of coal, to economize this precious fuel. coast; and thus enhance the price of I cannot, therefore, conclude this inte-Coal 'in those parts of England which resting subject without making some remarks upon a practice which can only castle for their supply; and finally, to
depend upon the Coal-field of Newbe viewed in the light of a national exhaust this Coal-field, at a period, calamity, demanding the attention of
nearer by at least one-third, than that to the legislature.
which it would last, if wisely econoWe have, during many years, wit- mized. (See Report of the Select Comnessed the disgraceful and almost incre- mittee of the House of Commons, on the dible fact, that more than a million state of the Coal Trade, 1830, page 242, chaldrons per annum, being nearly one and Bakewell's Introduction to Geology, third part of the best coals produced by 1833, pages 183 and 543. the mines near Newcastle, have been condemned to wanton waste, on a fiery needless legislative interference; but a
We are fully aware of the impolicy of heap perpetually blazing near the mouth broad line has ben drawn by nature beof almost every coal-pit in that dis- tween commodities annually or perioditrict. This destruction originated mainly in face, and that subterranean treasure,
cally reproduced by the soil on its sur* The interval between the suspending and sustaining foundation of Industry, piers of the Freiburg Bridge is about 870 which is laid by Nature in strata of English feet, and its clear span about 806 mineral Coal, whose amount is limited, feet. The Menai-Strait Bridge (same as and which, when once exhausted, is its span) is 522 feet.
As the Law most justly
gone for ever.
interferes to prevent thc wanton de- sources of posterity should permit us to struction of life and property, it should allow any extensive exportation of Coal seem also to be its duty to prevent all from a densely-peopled manufacturing needless waste of mineral fuel ; since country like our own; a large proporthe exhaustion of this fuel would irre- tion of whose present wealth is founded coverably paralyze the industry of mil- on machinery, which can be kept in lions. The tenant of the soil may neg- action only by the produce of our native lect, or cultivate his lands, and dispose Coal-mines, and whose prosperity can of his produce, as caprice or interest never survive the period of their exmay dictate ; the surface of his fields is haustion. —BUCKLAND's Bridgewater not consumed, but remains susceptible Treatise. of tillage by his successor; had he the physical power to annihilate the Land, Clerical Error in the American and thereby intlict an irremediable in
Patents-Law. jury, upon posterity, the legislature would justly interfere to prevent such In all the copies of the American Padestruction of the future resources of tents-Law passed in July last, which the nation.
have reached this country, there is a This highly-favoured country has been discrepancy as to the cost of the patent. enriched with mineral treasures in her Sect. 9 states that thirty dollars must strata of Coal, incomparably more pre
be paid on an application for a patent; cious than mines of silver or of gold. sect. 18 states that forty dollars must be From these sustaining sources of in- paid on an application for an extension dustry and wealth let us help ourselves of the term of a patent, “as in the abundantly, and liberally enjoy these case of an original application for a precious gifts of the Creator ; but let us patent." We find it the same in the not abuse them, or by wilful neglect and copy of the law printed in the Franklin wanton waste, destroy the foundations Journal, published at Philadelphia in of the industry of future generations.
September. This has led to an error Might not an easy remedy for this in Art. 2 (a) and 5 of the Tariff of Fees evil be found in a legislative enactment, published p. 252 of this Volume. Upon that all Coals from the ports of North- | inquiry, we are assured that to be corumberland and Durham, should be rect they should stand thus:shipped in the state in which they come from the pit, and forbidding by high
2. Application for Patent,
(a) If by a Citizen, or by an penalties the screening of any sea-borne Coals before they leave the port at which having made oath of an in. they are embarked. A law of this kind 5. Extension of Patent-Term ... 30...
tention to become Citizen .. 30... 6 15 0 would at once terminate that ruinous competition among the coal-ownerswhich
Patent-Law Grievance. No. VIII. has urged them to vie with each other in the wasteful destruction of small | The penalties inflicted on the inventive Coal, in order to increase the profits of genius of Britain during the present the coal-merchants, and gratify the pre- year, up to the 25th ult., in the shape of ference for large Coals on the part of government stamps and fees on patents, rich consumers; and would also afford amount to more than £36,000! the public a supply of Coals of every N.B. This sum has been paid in price and quality, which the use of the ready money, on taking the first steps, screen would enable him to accommo- and as many of the inventors are poor date to the demands of the various men, (operatives,) and a great many classes of the community.
others of them persons to whom it would A further consideration of national be very inconvenient to pay at least policy should prompt us to consider how £100 down, they have been obliged to go far the duty of supporting commercial into debt, or mortgage or dispose of their interests, and of husbanding the re- ) inventions, either wholly or in part, &c.
Alien-resident of a year,
6 15 0