636 GILDING 



Phenomena of Nature," about five years ago, and I resolved to put your theory to a 

 practical test. I accordingly had a case made, the sides of which were formed of 

 glass coloured blue or indigo, which case I attached to a small gns stove for en- 

 gendering heat ; in the case, shelves were fixed in the inside, on which were placed 

 small pots wherein the seeds to be tested were sown. 



' The results were all that could bo looked for ; the seeds freely germinating in from 

 two to five days only, instead of from eight to fourteen days as before. 



' I have not carried our experiments beyond the germination of seeds, so that I 

 cannot afford practical information as to the effect of other rays on the after- culture 

 of plants. 



'I have, however, made some trials with the yellow ray in preventing the germi- 

 nation of seeds, which have been successful ; and I have always found the violet r;iy 

 prejudicial to the growth of the plant after germination. 



' I remain, my dear Sir, very faithfully yours, 

 1 To Robert Hunt, Esq.' CHARLES LAWSON.' 



Another application of the principles involved in the discovery that the luminous 

 rays checked germination and promoted the growth of ligneous fibre has been mado 

 by the cultivators of early potatoes in the West of Cornwall. The seed potatoes are 

 carefully placed on shelves in houses maintained at such a temperature that germi- 

 nation is set up. When they begin to shoot, an abundance of light is admitted to 

 check the germinating process, and render the shoot woody and strong. In March 

 after the frosts these potatoes are carefully placed in the soil, and so rapid is their 

 growth and development that they are ready for the market in July. Upwards of 

 11,000 tons of potatoes, grown under these conditions, were sent from West Cornwall 

 in July 1874. 



GEROPIGA, or Jerupiga. A. factitious liquor, imported, from Portugal, and used 

 in this country for the adulteration of wines. It appears to be a compound of unfer- 

 mented grape-juice, brandy, sugar, and colouring matter. 



GERSDORFFITE. A sulpho-arsenide of nickel, containing, in typical 

 varieties arsenic, 45'5 ; sulphur, 19*4; nickel, 35'1. Found at Loos in Sweden, 

 near Hartzgerode in the Hartz, and Craigmuir Mine, Scotland. 



GEYSERITE. Siliceous sinter deposited from geysers or hot springs. 



GHU-NAI.A-PAAT. Corchorus olitorius or Hibiscus Manihot. An Indian 

 fibre much used by the natives. See FIBRES. 



GIBBSITE. A stalactitic hydrate of alumina, named after Colonel G. Gibbs, 

 whose collection of minerals is now in Yale College. 



GIBRALTAR STONE. Stalagmitic carbonate of lime resembling the 

 Algerian onyx-marble, found in limestone-caverns at Gibraltar. 



GIG MACHINES, are rotatory drums, mounted with thistles or wire teeth for 

 teazling cloth. See WOOLLEN MANUFACTURE. 



GIIiBERTITE. A micaceous mineral apparently related to kaolin, occurring 

 with the china-stone of St. Austell in Cornwall. 



GIIiDIXTG (Dorure, Fr. ; Vergoldung^QV.). This art consists in covering bodies 

 with a thin coat of gold, which may be done either by mechanical or chemical means. 

 The mechanical mode is the application of gold-leaf or gold-powder to various sur- 

 faces, and their fixation by different means. Thus gold may be appiled to wood, 

 plaster, pasteboard, leather; and to metals, such as silver, copper, iron, tin, and 

 bronze ; so that gilding, generally speaking, includes several arts, exercised by very 

 different classes of tradesmen. 



I. MECHANICAL GILDING. Oil-gilding is the first method under this head, as oil 

 is the fluid most generally used in the operation of this mechanical art. The follow- 

 ing process has been much extolled at Paris : 



1. A coat of impression is to be given first of all, namely, a coat of white lead paint, 

 made with drying linseed oil, containing very little oil of turpentine. 



2. Calcined ceruse is to bo ground very well with unboiled linseed oil, and tempered 

 with essence of turpentine, in proportion as it is laid on. Three or four coats of this 

 hard tint are to be applied evenly on the ornaments, and the parts which are to bo 

 most carefully gilded. 



3. The Gold colour is then to be smoothly applied. This is merely the dregs of the 

 colours, ground and tempered with oil, which remain in the little dish in which painters 

 clean their brushes. This substance is extremely rich and gluey ; after being ground 

 up, and passed through fine linen cloth, it. forms the ground for gold-leaf. 



4. When the gold colour is dry enough to catch hold of the leaf i^>M, this is 



on the cushion, cut into pieces and carefully applied with the pallet knife, pressed down 

 with cotton, and on the small ornaments with a fine brush. 



5. If the gildings be for outside exposure, as balconies, gratings, statues, &c., they 



