Diffuse 2 pounds of ground madder in 4 quarts of water, and after a maceration of 10 minutes, strain and squeeze the grounds in a press. Repeat this maceration, &c. twice upon the same portion of madder. It will now have a fine rose colour. It must then be mixed with 5 or 6 pounds of water and half a pound of bruised alum, and heated upon a water bath for 3 or 4 hours, with the addition of water, as it evaporates, after which the whole must be thrown upon a filter cloth. The liquor which passes is to be filtered through paper, and then precipitated by carbonate of potash. If the potash be added in three successive doses, three different lakes will be obtained, of successively diminishing beauty. The precipitates must be washed till the water comes off colourless.

Blue lakes are hardly ever prepared, as indigo, prussian blue, cobalt blue, and ultramarine, answer every purpose of blue pigments.

Green lakes are made by a mixture of yellow lakes with blue pigments; but chrome yellows mixed with blues produce almost all the requisite shades of green.

LAMINABLE is said of a metal which may be extended by passing between steel or hardened (chilled) cast-iron rollers.

For a description of metal rolling presses, see [Iron] and [Mint]; and

For a table of the relative laminability of metals, see [Ductility].

LAMIUM ALBUM, or the dead nettle, is said by Leuchs to afford in its leaves a greenish-yellow dye. The L. purpureum dyes a reddish-grey with salt of tin, and a greenish tint with iron liquor.

LAMPS differ so much in principle, form, and construction, as to render their description impossible, as a general subject of manufacture. In fact, the operations of the lampist, like those of the blacksmith, cabinet-maker, cooper, coppersmith, tinman, turner, &c., belong to a treatise upon handicraft trades. I shall here, however, introduce a tabular view of the relative light and economy of the lamps most generally known.

Kind of Lamps.Intensity of light duringMean
of 7
hours.		Consump-
tion per
hour in
grammes.		Light
from
100
parts
of oil.
1
hour		2
hours		3
hours		4
hours		5
hours		6
hours
1. Mechanical lamp
of Carcel		 - 100 42 238
2. Fountain lamp,
and a chimney with
flat wick		 -1009898979696125 11 113
3. Dome argand103907261423431 26·714116
4. Sinumbra lamp102958381786656 37·145150
5. Do. with fountain
above		 -100907052413285 43 197
6. Do. with another
beak		 -100979592898641 18 227
7. Girard’s hydrostatic
lamp		 -101968481767063·6634·714182
8. Thilorier’s or
Parker’s do. lamp		 -106103100949290107·6651·143215