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Show !GO APPENDIX. ture becomes condensed into water-as dew, fog, clouds, rain, mist, and (wh~n frozen) into frost, slee~, snow, and hail; t~1e temperature at which this condensation commences, ts called the d~w pomt. 'Vhencver the temperature of the air is the san~e , or a liu.lc below the dew point, the vapor turns to water, and forms what·~ cal.led mzst or c~oudif it be much below, (yet above 32°,) the condcnsatwn 18 more rapu.l, and 1'ain is form cd-ifbeJow 32°1 SHOW is formed. \¥hen the ascending column of air carries the rain into the region of perpetual congelation, that rain is frozen and descends in small pieces of ice, called hail. VVhen the temperature of the swface of the earth is a lillie below the temperature of the air, a condensation of the vapor in the air (at the ~urface) takes place and forms dew-should the temperature of the air, at that time, happen to be below 32° of Fahrenheit, the dew is frozen and forms frost. \Vhen the temperature of the ground is considerably below that of the air, a much more extensive condensation takes place, ami thus a fog is produced; should the temperature of the air at that time be much below 32°, the fog is frozen, and is then snow, and falls to the earth by its specific gravity. in proportion to the extent of cold surface which comes in contact with the air, so will be the quantity of fog produced ; this can never be so great in a level country, as in a narrow valley or a large town-London, for instance, where the paved streets, the walls, and the roof:; of the houses, form a much g reater extent of cold surface in a given space, than would occur in an open country. In proportion as the town is more closely built up, the greater will be the effect proJuced. Consequently, as we approach the suburbs, where the buildings are further apart ami the openings greater, the fog will proportionably decrease; and thus the centre of the town may be the centre of the fog. But the circums tances above described do not always produce a fogfor it may so happen, that at some place not far distant the air is s utficiently heated to ereatc an upward motion, ami there ascends in an upward co!umn to a great height; this causes a strong wind to rush towarJs that upward column, carrying the fog away with it, and thus keeps the atmosphere comparatively clear; J1ence we seldom see much fog on a windy day. If the retums of this dense fog are periodical, the reason is, that like causes produce like efi'ccts; and the same cireumstances which cause one fog, occurring again will cause anotAer. I am not aware that it returns at regular intervals. The location of London on an island, surrounded by the ocean, the humidity of its atmosphere, its northern latitude, its great extent of paved streets, its numerous and elevated buildings, all have a tendency to cause dense and frequent fogs. It is probable that the great fogs alluded to, are c21.used by a sudden rise in the temperature of the air, (ow ing to a storm passing to the northward of the island.) The paved streets, the walls, and the roofs of the houses, being much colder than the air, causes the great and sudden conJensation of the vapor into fog. SOUTIIII:UN EXUL'fA'flUN. 107 No. III. 'VE give below some s pecimens of Southern exultation over the burning of our Hall, afl"ording the s urest evidence that slavery cannot long ex ist where buildings are open for a free discussion of " its sublime merits." Some of the writers: according to their own confessions, took part in the mob.' One of our newspaper eJitors, in commenting on them, says : " Alas !-for the honor of the Keystone State, when she is thus subjected to the eulogy of unhung scoundrels, who exult in her infamy and commend her for her shame. But are P ennsylvania principles to be trampled under foot-the majesty of her laws insulted, and the property of her citiz~ns destroyed by ruflians from other states, and no atwmpt be made to brrng the self ackno.wledged criminals to jnstice? \Vhat have become of our rights,of the power of a state to proteet her own citizens,-if our laws may thus be practically nullified in the very teeth of their constituted guarJians, by proltiiTates from the South, who publicly boast of their succe:ssful v!llany, and ex~ It in their crimes, as if conscious that Pennsylvania is too weak or too wicl;:ed to vindicate her laws, or protect her citizens i11 the exercise of their constitutional rights?" The first is from the New Orleans True American, of May 26. The editor of that paper says : "The news from Philadelphia is of a highly important and interesting character. It will be seen by the subjoined letter from a private correspondtmt, that the Hall of the abolitionists in that city has been burnt to the ground; and yet, great as the destruction was, so tmiversal was the feeling that dictated it, and so well considered were all the measures taken to e fTect the purpose, that ne ither fights, drunkenness, or disorder, s tained the act, which the citizens undertook from a heart· felt conviction that their act, though contrary to the ~pirit of the !aw, was called for by a firm conviction that the eOOrts and purposes of the vile abolition faction tended to destroy the Union! to introduce murder, anarchy, and rapine, into the homes of their Southern brethren l and merely to serve the purposes of a few selfish bigots, that our frui!ful and happy country wouiJ be rendered a scene of carnage and miRery, of which the horrid tragedy of St. Domingo, would be an inconsiderable and faint semblance. VVe will not, however, spoil the interest which (lur correspondenl's letlcr-himself an eye wilness of the scene-must give our readers, from its vivid description and graphic accuracy." PmLADELPliiA, l\fay 18, 1838. To the E<lilor of the New Odcans Tl'llc American. Great E xcitement in Philculelphia-the /Jbolition !louse, called the Pennsylvania /fall, burnt to as!tes by a collection of people, four or five thousand in number-Pennsylvania, and Philadelphia in pm·ticulaJ", deliveJ ·ed and secure from the macldnations of the Fanatics. A building recently erected by the Abolitionists in this city, and called by them the u Pennsylvania Hall," and which cost forty-three thousand dollars, part contributed by English Fanatics, was formally opened last Monday, the 14th inst., by the abolitionists, preceded by a speech by David Paul Brown, Esq. On Tuesday the 15th, a meeting was held by the Female Anti-Slavery Convention in the said Hall, an account of which I have sent you by the slow mail. At night a lecture was delivered on slavery, before an audience promiscuously mixed up of blacks and whites, s itting |