_ The grounds thus prepared do 
mot crack; they may be painted 
upon a very shoct time after being 
laid, and from their absorbent qua- 
lity, allow the business to be pro- 
‘ceeded upon with greater facility 
and better elfect, than, with those 
prepared in the usual mode. 
— 
Method of purifying Oil for Painting. 
Make some of the bone-ashes 
into a paste with a little water, so 
as to form a massor ball; put this 
‘ball into the fire, and make it red- 
hot; then immerse it for an hour, 
in a quantity of raw linseed oil, 
-suffeient to cover it: when cold, 
pour the oil into bottles, add toit a 
little bone-ash, let it stand to settle, 
and in a day it will be clear and fit 
for use. 
IVhite Colour 
Is made by calcining the bone of 
sheep’s trotters in a clear open fire, 
till they become a perfect white, 
which will never change. 
Brown Colour 
Js made from bones in a similar 
manner, only calcining them in a 
crucible instead of an open fire. 
Yellow Colour ; or, Masticot. 
Take a piece of soft brick, of 
a yellowish colour, and burn it in 
the fire; then take forevery pound 
of brick, a quarter of a pound of 
flake-white, grind them together, 
and calcine them; afterwards wash 
the mixture, to separate the sand, 
and let the finer parts gradually dry 
for use. 
Red Colour, equal to Indian Red. 
Take some of the pyrites, usually 
found in coal- pits, calcine them, and 
they will produce a beautiful red. 
USEFUL PROJECTS. 
979 
Grey Colour 
Is made by calcining together 
blue-slate and bone-ashes powdered, 
grinding them #ogether, afterwards 
washing them, and drying the mix~ 
ture gradually. 
Blue Black 
Is made by burning vine-stalks in 
a close crucible in a slow fire, till a 
perfect charcoal is made of them, 
which must’ be well ground for use. 
Crayons 
Are made of bone-ash powder 
mixed with spermaceti, adding 
thereto the colouring matters. The 
proper proportion is, three ounces 
of spermaceti to one pound of the 
powder. ‘The spermaceti to be first 
dissolved in a pint of boiling water,_ 
then the white bone-ash added, and 
the whole to be well ground toge- 
ther, with as much of the colouring- 
matter as may be necessary for the 
shade of colour wanted. They.are 
then to be rolled up in the pro- 
per form, and gradually dried upon 
a board, 
White Chalk, 
If required to work soft, is made 
by adding a quarter of a pound of 
whitening to one pound of the bone- 
ash powder; otherwise the bone- 
ash powder will answer alone. The 
coloured chalks are made by grind- 
ing the colouring-matter with bone~ 
ashes. 
On Means of assisting Persons in 
Danger of Drowning. By Mr, 
H. Lawson, —( Phil, Mag.) 
Vhe absolute necessity that assise 
tance to persons in danger of drown. 
ing should be speedy to be effectual, 
induced Mr, Lawson’ to consider 
what articles were most readily and 
3R2 universally 
