LIG
107
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“ rin S f og or rain, the glare of the fire was visible byin the atmosphere, though the fire itself could not
j^.The North Foreland lighthouse, between Ramsgate anda rgate will be more familiar to many of our readers thany other, and will serve as an excellent example of the pro-„ .. ss °f illumination. This lighthouse was erected for indi-um ' ri g the proximity of the Goodwin Sands. The first inti-tv 8 ion we have of its existence is in 1636, in Charles theto . rei S n > when license was granted to Sir John Meldrumj lo lenew and continue this and the South Foreland light-er S6 ^° r t ^ e same purpose. At this time it was merely a? e glass lantern on the top of a timber-and-plaister house,Ce lc “ Was burnt in 1683. Towards the end of the sameoctao*^’ ^ le P resen i tower was partially erected ; a strongbur ^° Ua ^ str ucture, having the iron grate, or chauffer, forflaru' 11 ^ c °al s - From the difficulty of keeping up a propery ea 6 , i n win dy or rainy weather, it was covered about theI 32, with a sort of lantern, with large sash windows,wj - lle coal fire was kept alight by means of large bellows,(■ j tbe attendants blew throughout the night. This was"'as tl n0t to answer > an d the reflected glare above-mentionedand l° u pbt desirable. Accordingly, the lantern was removed,0tl 16 bre restored to its original condition. Matters wenti 7 0 Us till 1790, when the tower was raised to the height of
feet, and further improvements made in the lantern, by theproduction of lamps
described.
Afte
and other apparatus, hereafter to be
ntar' 6r some alterations of the Cordouan wood-fire, thedi st , lners complained that they could not see the light at aU S ce °f two leagues, as formerly. But Smeaton informsSouth' 1 ^ le ooa '‘b re of the Spurn Point lighthouse, at thep r ; ( . °f tbe Humber, which was constructed on a goodrpppie for burning, had been seen thirty miles off.ligj lt p ° n \y exceptions to the fires were the noble Eddystonecaotp’ w bich then exhibited a chandelier of twenty-four waxbou Se p’ ^ ve °f which weighed 21bs., and the Liverpool light-'pp 8 ’ w bich had oil lamps, with rude reflectors.oti e st . COal f'gbts are now quite abolished. The last was atNidi n atl011 belonging to Sweden , on the little island oft° 6 p’ 011 the east side of the Cattegat , near the entranceCoaj fi t* c sea. These were two light towers, showingfrom tif 3 ’ ^ut surrounded by sides of glass, to shelter themthe p . e w * n d, and open at the top. They were altered atX he . n ' n g of the year 1846.
a< f"anc Ultro< f uc tion of the Argand lamp was the first great•Sent in to 'y ar ds the perfection of lighthouses. This improve-'iuoti 0n p^f'cial light was the greatest, previous to the intro-°f (Jenp ° l ® as ‘ f t was discovered by M. Argand, a citizen>> and } a> a P ut 1780 or 1785. It has remained as he leftIts pe r f 1U . P rrt >ciple appears as perfect as can be looked for.youogjp 10 " as an experiment was almost accidental. TheCovb..- r °ther of Argand thus describes its accidental dis-
e ry « ^ er °f Argand thus describes its accidental dis-cing j • . % brother,” he says, “ had long been trying tolying o 8 | am P to bejr. A broken-off neck of a flask was! a bl 6) “e chimney-piece ; I happened to reach it over thelp^edia,. , to place it over the circular flame of the lamp ;b>s Seat . ®*y it rose with brilliancy. My brother started from^braced ecstas y> rushed upon me with a transport of joy, and.. On t j le ® e with rapture.” Thus originated the Argand lamp.!'°0, at)( j ‘utroduetion of a more efficient means of illumina-tl0| Jseg ag le consequent abandonment of the coal fires, light-a . a 'l th ev SUrne< l a more important position in maritime affairs,..bis ex 7 "'ere, accordingly, largely increased in number.5® tUeana S c° n ren( l ere d necessary another improvement—ot readily distinguishing one light from another.man y suggestions have been made for doing this
more effectually—some practicable, others not so, and someare in actual operation—this part of the science is far frombeing in a perfect state. Much remains to be done, beforethe mariner can be certain of determining, by its distinctivefeatures, each light when seen.
The variety of lights that have been proposed and experi-mented on for lighthouse purposes is very great, particularly,we may mention, the Drummond, the electric, voltaic, &c.,but few have stood the test of experience ; and the lampsnow in universal use are still but modifications of the originalArgand burner.
Amongst the means for increasing the intensity of light,the use of reflectors is most important. In the year 1786,reflectors and oil lamps were first proposed at a meeting ofthe Scottish lighthouse commissioners. The first metallicreflectors used in the northern lighthouses were constructedby Mr. Thomas Smith, of Edinburgh . The figure was given ito them by a plaster mould, and the cavity was afterwardsfilled in, by means of cement, with small facets of mirror-glass. This must have done its work very imperfectly,although the general figure was capable of considerableaccuracy. In 1803, the first polished metal reflectors usedin Scotland were placed in Inch-Keith lighthouse ; sincethen, various slight alterations and improvements have beenmade, but substantially, the system of illuminating light-houses remains the same.
We cannot conclude this article without acknowledgingour obligations in its preparation to the valuable paper onlighthouses, &c., by Mr. Findlay.
LIKE ARCS, in the projection of the sphere, the partsof lesser circles containing an equal number of degrees withthe corresponding arcs of greater circles.
LIKE FIGURES, in geometry, such as have their anglesequal, and the sides about the equal angles proportional.
LIKE SOLIDS, such as are contained under like !planes. j
LIMESTONE , a calcareous stone, which, being sufficiently !burned or calcined, falls into powder on the application of !water ; and being then mixed with water and sand in certainproportions, forms a strong cement. !
Limestone is either pure or mixed. The best for the use jof building is that which contains a certain portion of clayand iron. See Cement.
Lime-Kiln, a kiln for the purpose of burning lime. Kilnsfor this purpose are constructed in a variety of ways, to saveexpense, or to answer to the particular nature of the fuel.
Lime, quick, a term applied to lime in its most powerfulor caustic state, before it has been rendered mild by theabsorption of carbonic acid gas, or fixed air. See Cement-Kiln.
LINE, (from the Latin , linea,) a quantity extended inlength only. A line may be conceived to be formed by the imotion of a point. Lines have no real existence except at |
the termination or terminations of the surface of a body: |
thus, a line is the junction of two surfaces, and therefore can jhave no thickness. \ '
Lines are of two kinds, viz., straight or curved. Straight j \lines are all of the same species ; the species of curves, ; iwhich are infinite, are divided into geometrical and me-chanical. \
Line, also denotes a French measure, containing the 12tli jpart of an inch, or the 144th part of a foot. j
Line, Equinoctial, the common intersection of the equi-noctial and the dial planes. _ :
Line, Geometrical, in perspective, any straight line in the igeometrical or primary line. !