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not wonder at our going wide from Formation of Nebula; the path of truth and nature ; but " Form I. In the first place, these will vanish like the Cartesian since we have supposed the stars to vortices, that soon gave way when be of various fizes, it will frequent. better theories were offered. Only happen that a ftar, being conthe other hand, if we add observati- fiderably larger than its neighbour. on to observation, without attempt- ing ones, will attract them more ing to draw not only certain con-' than they will be attracted by others clusions, but also conjectural views that are immediately around them; from them, we offend against the by which means they will be, in very end for which only observa. time, as it were condensed about a tions ought to be made. I will en- centre; or, in other words, form deavour to keep a proper medium; themselves into a clufier of stars of .but if I should deviatc from that, I almost a globular figure, more or could wiih not to fall into the latter less regularly fo, according to the error.
size and original diitance of the " That the milky way is a most furrounding stars. The perturbe. extensive stratum of stars of vari- tions of these mutual attractions ous sizes admits no longer of the must undoubtedly be very intrileast doubt ; and that our sun is cate, as we may easily coinprehead actually one of the heavenly bodies by confidering what lir Ifaac Nex. belonging to it is as evident. I ton Pays in the first book of his have now viewed and gaged this Principia, in the 28th and follow. Shining zone in almost every di- ing problems. But, in order to aprection, and find it composed of ply this great author's reasoning of tars whose number, by the account bodies moving in ellipses to fuch as of these gages, constantly increases are here, for a while, supposed to and decreases in proportion to its have no other motion than what apparent brightness to the naked their mutual gravity has imparted eye. But, in order to develop the to them, we must suppose the con ideas of the universe, that have jugate axes of these ellipses indefbeen suggested by my late observa- nitely diminished, whereby the et tions, it will be best to take the lipses will become twight lines. fubject froin a point of view at a Form II. The next cale, confiderable dillance both of space which will also happen almost as and of timc.
frequently as the former, is where
a few ttars, though not fuperior in Theoretical View.
fize to the rest, may chance to be * Let us then suppose number- rather nearer each other than the less bars, of various sizes, scatter- surrounding ones ; for here alio ed over an indefinite portion of will be formed a prevailing attraco space in such a manner as to be al. tion in the combined contre uf'gramost equally distributed throughout vity of them all, which will occk the whole. The laws of attraction, fion the neighbouring liars to draw which no doubt extend to the re- together; not indeed so as to form inotest regions of the fixed Itars, a regular or globular figure, but will operate in such a manner as however in such a manner as to be most probably to produce the fol. condensed towards the common cen. lowing remarkable effects.
tre of gravity of the whole irre
rated with water; and it would only mosphere is electrified, but much vield to us, what it could not retain stronger in frosty, than in warm in folution.
weather, and by no means less in • " 4. It is universally allowed, the night than in the day : it is likce that heat contributes very much tv- wife stronger in elevated than in wards converting waterinto vapour, low places. From these facts we which is again condensed by cold. may be enabled to account, why In whit manner will the doctrine of evaporation is carried on during folution account for the spontaneous very cold weather. All the heat evaporation of water, and its being contained in water, above what is suspended in air, in the coldest wea- sufficient to keep it in a fluid state, ther, cven when the thermometer is will convert it into vapour; which, below the freezing point? Though in a north or northeast wind, when I cannot allow of Tuch a solution as the clectric matter greatly abounds, above mentioned, I can, however, will be carried off with much rapi. readily admit of a strong attraction dity; and, by the power of electri. betwixt air and water : tor no air is city, will be rendered still lighter. found without water, and no water the higher it ascends ; each particle without air.
repelling each other, and prevento " Water, which is eight hundred ing the cold from condensing the times heavier than air, by a very vapour, in its afcent through the Imall degree of heat may be con- cold regions of the atmosphere. verted into vapour, which vapour is The higher it rises, the more space one thousand eight hundred times there is for expansion; and the more lighter than air, according to Mr. it is expanded, the clearer will the Watt. It confequently follows, that atmosphere appear, and, probably, vapour will rile up in the atmo- the higher the mercury will rise in fphere, to the height of its own the barometer. specific gravity ; but, long before i “ It likewise appears, that the it could reach to fo high a region, it electric matter is more sensible near would be condensed by cold, and the surface of the earth, in cold return to the earth in rain, were it northern countries, than in warm not for the latent heat it contains, fouthern places. M. Volta, with a and the electric matter in the air. very simple apparatus, on the up.
" Whatever I mention concern- per gallery of St. Paul's, produced ing electricity is from facts, and not an electric fpark, which, he told from any theory written about it, me, in Italy, could not be done, which is above my comprehension. but on a very high mountain, or in But as the terms now in use, viz. a fituation greatly elevated. This positive and negative, or plus and seems a wise provision in nature, minus, are generally best under- that the electric matter Nould apo stood, I shall express myself by pear near the surface of the earth them. The able Nollet has proved, in cold climates, to raise up and that water electrified, will evaporate suspend the vapour in the air, which faster, than water which is not elec. otherways would be condensed by trified. Does is not follow, that the cold; whereas, in warm coun. the more electric matter is in the tries, the heat of the earth will be air, the quicker the evaporation of sufficient to raise vapours to a great water will be? And Mr. Cavallo height, which are afterwards car. has proved, that at all times the at. ried. still higher, by the electric mat.
ter in the upper regions. This, the same, and generally, heavy rain perhaps, is the cause, why the air immediately, or soon after, follows : is so clear and transparent in warm this is well known to the inhabitants climates.
of, and travellers among, moun. “ By making some obfervations tains, on the falling of rain, we shall have “ From this we can casily ac. other proofs, that the electric mate count, why thunder-showers are ofter is the great cause by which vaten partial, falling near, or among pour is supported in the atmosphere. mountains, and the rain in such Here I must observe a fact, well quantities, as co occasion rivers to known to all present, that bodies be overflowed; whilit, at the dielectrified, by the same electric stance of a few miles, the ground power (no matter whether positive continues parched up with drought, or negative) repel each other; and, and the roads covered with duit. when electrified by the different “ It often happens, that one clap powers, that is, the one plus and of thunder is not sufficient to pro. the other minus, attraet each other : duce rain from a cloud, nor even a on coming into contact, an equili- second : in short, the claps must be brium is restored, and neither of repeated, till an equilibrium is rethem will shew any signs of electri- stored, and then the rain mult, of city.
consequence, fall. Sometimes we 6 From this it follows : if two may have violent thunder and light. clouds are electrified by the fame ning without rain, and the black power, they will repet each other, appearance of the heavens may be and the vapour be suspended in changed to a clear transparent lky, both; but, when one is positive and especially in warm weather. To the other ncgative, they will attract account for this, it must be reinem. each other, and restore an equili. bered, us I lately said, that one or brium. The electric power, by more claps of thunder are not alwhich the vapour was suspended, ways fufficient to produce rain from being now destroyed by the mutual the clouds : fo, if an equilibrium action of the clouds on each other, be not restored, little or no rain will the particles of water will have an fall, and in a short time the electric opportunity of running together matter, passing from the earth to into each other, and, as they aug- the clouds, or the superabundant ment in fize, will gain a greater quantity in the air, will electrify degree of gravity, descending in those black clouds, by which means small rain, or a heavy Mhower, ac- the particles of vapour will be ex. cording to circumstances.
panded, raised higher, and the air " A cloud, highly electrified, become clear. Clouds may be meltpaffing over a high building or ed away, even when we are looking mountain, may be attracted by, and at them, by another causc, that is, be deprived of its electricity, with by the heat of the fun. We know, pur or with a violent explosion of that transparent bodies are not beatthunder. If the cloud is electrified ed by the fun, but opaque ones are; plus, the fire will defcend from the the clouds being opaque bodies, are cloud to the mountain ; but, if it be warmed by the rays of the sun shinelectrified minus, the fire will as- ing on them, and any additional çend from the mountain to the quantity of heat will rarify the vacloud. In both cases, the effect is pour, and occation its expanding in
the air, which will soon become point to fair. For this reason, the transparent. When vapour is made itones of halls, and smooth fub. to expand more than it would o. flances, are often bedewed with wet, therwise do, a certain quantity of in dry warm weather (that is, the absolute heat is neceflary to keep it air is in a state to part with its moiin the form of vapour; therefore, ture), and, vice versa, they will when the receiver of an air-pump dry in the time of rain. . is exhausting, it appears muddy, « Left this paper should exceed and a number of drops are found the common limits of time in readwithin it; the moisture contained ing, I shall pass over those observa. in the air, in the form of vapour, tions, which might be made on fogs being made to occupy a greater or mists; a few excepted, which I space than what is natural to it, and shall here subjoin. receiving no addition of heat, a 66 Fogs are produced by two part of it is condensed. .
causes as different as their effects are " If, therefore, the air is sud- opposite." A fog may be produced denly rarified, a few drops of rain by a precipitation of rain, in very will defcend, as may often be ob- small particles, like a cloud floating served in the summer season. on the surface of the earth. In
“ I have repeatedly observed, es- this case the air is moist and damp, pecially during the summer, when and never fails to wet a traveller's the wind is at north-east, that the cloaths; the stones of the street, weather is, in general, cold and painted doors, and hard, cool, dry, with a clear atmosphere. smooth bodies, are generally coverShould the wind suddenly change ed with moisture, which often runs to south-west, in a few hours, black in large drops : this, I dare say, clouds begin to gather, vegetables has been observed by every person. look fickly, and droop their leaves ; Secondly, a fog may be produced and, soon after, comes on a violent by the absorption of moisture, when storm of thunder, with heavy rain. the air is too dry, and differs from
" This change, I imagine, is not the other just described; for it will so much owing to the south-west not impart any of its moisture even wind bringing rain, as to the atmo- to dry bodies; no damp is to be met sphere's being changed from an with on stones, polised marble, electric ftate, capable of suspending &c. This fact is well known to the vapour, to a state of parting with inhabitants on the sea-coast of Fifeits moisture. As soon as the storm shire, who, during their summer is going off, vegetables revive from months, have frequent opportuni. their languid state, and the air re- ties of observing a fog in the after. covers its usual aspect. From this noon, driving up the Firth of Forth, we may conclude, that no instru- with a drying east wind, which of. ment can be made to ascertain the ten blasts the trees and young vegetquantity of moisture in the air : all ables, and, therefore, in a small that is, or ought to be expected degree, resembles the Harmattan in from a hygrometer, is to shew, whe- drying up the ground, and robbing ther the air be in a state to retain or vegetables of their moisture. part with its moisture. In appa- « I shall now conclude with a rent dry weather it may pomt to fhort summary of the whole. rain; and when it rains, it may "1, Thạt heat is the great cause, story which I have been able to long dead, or more probably de consult, incline me to believe it to ftroyed by the motion of the rocks be a non-defcript. As the pecu- in the storm : fome few of the liarities of its structure may add to brain-stones, however, that had been the knowledge of the natural hi- thrown beyond the reef, and lods. itory of other animals of this ge- ed in the shoal water, receiving less nus, at present fo little understood, injury, the animals were preserved I have drawn out a more particular unhurt. account of it ; which, if you think " The animal, with the shell, is it deserves attention, you may pre- almost intirely inclosed in the brainsent to the Royal Society.
ftone, fo that at the depth in which « This animal was found on the they generally lie, they are hardly fouth-east coast of Barbadoes, close discernible through the water from to Charles Fort, about a mile from the common surface of the brainBridge Town, in fome thoal wa- stone; but when in search of food, ter, separated from the sea by the they throw up two cones, with ftones and fand thrown up by the membranes twiited round them in a dreadful hurricane, which happen- spiral manner, which have a loose ed in the year 1780, and did so fringed edge, looking at the botmuch mischief to the island. tom of the sea like two flowers;
"The wind, in the beginning and in this state they were discoof the storm, which was in the af- vered. ternoon, blew very furioully from “ The species of Actinia, called the north-west, making a prodigi. in Barbadoes the animal power, ous swell in the sea ; and in the and common to many parts of that middle of the night changing sud- itland, although rarely before scen denly to the south-east, it blew from on this part of the coast, was now that quarter upon the sea, already found in considerable numbers in agitated, forcing it upon the shore this thoal water. with so much violence, that it threw " The animal was first observed down the rampart of Fort Charles, by captain Hendie, the officer comwhich was opposed to it, although manding Fort Charles, in looking thirty feet broad, by the bursting for sells which were thrown up of one sea. It forced up, at the in great pumbers from the bottom same time, immenfe quantities of of the harbour. He found a piece large coral rocks from the bottom of brain-stone containing three of of the bay, making a reef along them in different parts of it. Some this part of the coast for the extent little time after, I was lucky enough of several miles, at only a few yards to find another brain-stone with distance from the shore.
two in it; one of them is the spe66 The foundings of the harbour cimen in your pofleifion ; the other were found afterwards to be intire. was destined for examination, of ly changed, by the quantity of ma- which the following is the account. terials removed from the bottom in " The animal, when taken out different places. In the reef of co- of the thell, including the two cones ral was found an infinite number of and their membranes, is five inchei large pieces of brain stone, con- in length; of which the body is taining the mell of this animal; three inches and three-quarters, but the animals had either been and the apparatus for catching its