LIG 



LIG 



we find, that as its wick lengthens, the 

 light indeed becomes less, and the cup be- 

 comes filled with melted wax. The wick, 

 however, being thin and flexible, does 

 not long occupy its place in the centre of 

 the flame ; neither does it, when there, 

 enlarge the diameter of the flame, so as 

 to prevent the access of air to its internal 

 part. When its length is too great for 

 the vertical position, it bends on one side ; 

 and its extremity, coming into contact 

 with the air, is burned to ashes, except- 

 ing such a portion as is defended by the 

 continual afflux of melted wax, which is 

 volatilized and completely burned by the 

 surrounding flame. We see, therefore, 

 that the difficult fusibility of wax renders 

 it practicable to burn a large quantity of 

 fluid by means of a small wick ; and that 

 this small wick, by turning on one side 

 in consequence of its flexibility, performs 

 the operation of snuffing upon itself, in 

 a much more accurate manner than it 

 can ever be performed mechanically. 



Mr. Henry made some experiments on 

 the light afforded by the combustion of 

 different gases, and found, that it was ap- 

 parently in the ratio of the oxygen that 

 entered into combination with the hydro- 

 gen they contained. Thus, 100 parts of 

 pure hydrogen gas required from 50 to 

 54 of oxygen ; 100 of gas from oak, 42 ; 

 from moist charcoal and from dried peat, 

 each 50 ; from lamp oil 136 ; from coal 

 140; from wax 166; pure olifiant gas 

 210. Tallow is nearly on a par with oil. 

 The production of light from the first 

 four was so trifling, that they did not 

 seem applicable to (economical purposes. 



LIGHT from plants. In Sweden a very 

 curious phenomena has been observed on 

 certain flowers by M. Haggern, lecturer 

 in natural history. One evening lie per- 

 ceived a faint flash of light repeatedly 

 dart from a marigold. Surprised at such 

 an uncommon appearance, he resolved to 

 examine it with attention ; and, to be 

 assured it was no deception of the eye, 

 he placed a man near him, with orders to 

 make a signal at. the moment when he 

 observed the light. They both saw it 

 constantly at the same moment. The 

 light was most brilliant on marigolds of 

 an orange or flame colour; but scarcely 

 visible on pale ones. The flash was fre- 

 quently seen on the same flower two or 

 three times in quick succession, but more 

 commonly at intervals of several minutes: 

 and when several flowers in the same 

 place emitted their light together, it 

 could be observed at a considerable dis- 

 tance. This phenomenon was remarked 



in the months of July and August at sun- 

 set, and for half an hour when the at- 

 mosphere was clear ; but after a rainy 

 day, or when the air was loaded with va- 

 pours, nothing of it was seen. The follow- 

 ing flowers emitted flashes, more or less 

 vivid, in this order : 1. The marigold, ca- 

 lendula officinalis. 2. Monk's-hood, tro- 

 pseolum majus. 3. The orange lily, lilium 

 bulbiferum. 4. The Indian pink, tagetes 

 patula et erecta. 



To discover whether some little insects 

 or phosphoric worms might not be the 

 cause of it, the flowers were carefully ex- 

 amined, even with a microscope, without 

 any such thing being found. From the 

 rapidity of the flash, and other circum- 

 stances, it may be conjectured that there 

 is something of electricity in this pheno- 

 menon. It is well known, that when the 

 pistil of a flower is impregnated, the pol- 

 len bursts away by its elasticity, with 

 which electricity may be combined. But 

 M. Haggern, after having observed the 

 flash from the orange lily, the antherx of 

 which are a considerable space distant 

 from the petals, found that the light pro- 

 ceeded from the petals only ; whence he 

 concludes, that this electric light is caused 

 by the pollen, which, in flying off, is 

 scattered oil the petals. Whatever be 

 the cause, the effect is singular and highly 

 curious. 



LIGHT house, a building erected upon a 

 cape or promontory on the sea coast, or 

 upon some rock in the sea, and having on 

 its top in the night time a great fire, or 

 light formed by candles, which is con- 

 stantly attended by some careful person, 

 so as to be seen at a great distance from 

 the hind. It is used to direct the shipping 

 on the coast, that might otherwise run 

 ashore, or steer an improper course, 

 when the darkness of the night and the 

 uncertainty of currents, &c. might render 

 their situation with regard to the shore 

 extremely doubtful. Lamp-lights are, on 

 many accounts, preferable to coal fires or 

 candles ; and the effect of these may be 

 increased by placing them either behind 

 glass hemispheres, or before properly dis- 

 posed glass or metal reflectors, which last 

 method is now very generally adopted. 

 See BEACONS. 



LIGHTFOOTIA, in botany, so named 

 in honour of John Lightfoot, a genus of 

 the Polygamia Dioecia class and order. 

 Essential character: calyx four-leaved; 

 corolla none : female and hermaphrodite, 

 stigma sessile ; berry umbilicated, one- 

 celled, with from three to six seeds. 

 There are three species, all shrubs. 

 LIGHTNING. It is now universally 



