408 
POPULAR SCIENCE REVIEW. 
had occasion to test a powder called green cinnabar, found that it was com- 
posed of prussian blue and chrome yellow, and reports that, although 
from the nature of the prussian blue it is not applicable for the painting 
of walls containing lime, or fit for colouring sweetmeats and other edible 
compounds, it is well adapted to supply the place of the dangerous 
arsenical green pigments used in paper staining, and may be produced 
in every shade, from the lightest to the darkest. The following is the 
method given for producing the pigment : — Mix together, in the first place, 
solutions of yellow chromate and yellow prussiate of potash ; next take 
solutions of the acetate of lead and iron ; mix these also together and then 
with the former compound, and a green precipitate will be produced, the 
tint of which will depend on the proportions of the various ingredients ; 
the greater the quantity of the prussiate of potash and acetate of lead 
employed, the lighter, of course, will be the colour. The precipitate must 
be carefully washed and dried with a gentle heat. Dr. Eisner recommends 
the production of the acetate of iron by the precipitation of a solution of 
acetate of lead by means of sulphate of iron, and the filtering the residuary 
liquor. 
The Effect of Syrups on Linen. — A French chemist has made some 
interesting experiments on the effect of syrup on textile fabrics. A piece 
of cambric was brought to him which seemed to have been burned by 
an acid, but which in fact had only had some drops of syrup of tolu 
dropped upon it. The chemist, M. P. Dore, tested the remainder of the 
liquid, and found it perfectly pure, consisting only of balsam of tolu, 
sugar, and water. He then dropped some of the same syrup on a piece 
of linen and dried it, and found to his surprise that it had rendered 
the fabric perfectly rotten. He sought for the cause of this apparent 
phenomenon, and came to the conclusion that it resulted simply from the 
rigidity given to the fibres by the absorption of the sugar. It is •well 
known that frozen linen, or that which has been much starched, is brittle 
from a like cause. M. Dore says, that certain French weavers strengthen 
the threads of their warps by means of paste, but that as the effect would 
be lost by dryness, the unfortunate men are compelled to work in damp 
rooms and even in cellars. 
Mechanical Perforation of Rocks. — A young engineer named 
Leschot, has invented a curious method of piercing rocks for mining 
purposes. Many attempts have been made in this direction, but with 
little success, and M. Leschot has hit upon the happy expedient of cutting 
out a solid cylindrical piece, instead of making his machine act upon the 
whole surface of the matter to be removed, thereby avoiding an immense 
amount of labour, and saving a vast deal of time. The new cutter is 
tubular, and its effect is to isolate a small column of the material, which 
can easily be removed by the action of a wedge. It consists of an iron 
tube whose outer diameter is equal to that of the required hole, and 
furnished with a steel ring carrying what may be called a crown of 
diamonds. The tubular piercer is made to revolve by machinery, and is at 
the same time pressed forward, making a circular incision in the rock, and 
the dust is prevented from accumulating by a current of water which is 
forced down the tube, and which at the same time prevents the heating of 
