186 Experiments on the Composition of 
low stone-paper, in which M. Servin observed some 
traces of martial vitriol (sulphat of iron). 
Though I made a number of experiments in order to 
discover the composition of this slate, I shall here 
mention those only which were attended with the best 
success. But, to avoid repetition, I shall first describe 
that previous manipulation which appeared most conve- 
nient. 
The red or white bole, carpenters* ochre and chalk, 
which I employed for this use, were reduced to a fine 
powder. A pulpy mass of the coarsest kind, procured 
from a paper manufactory, after being macerated in wa- 
ter, was strongly pressed and weighed out for use. The 
weight was increased about two thirds by the moisture. 
In giving an account of the following experiments, I shall 
mention the weight of this substance as alluding to it when 
dry. 
The glue was dissolved in a moderate quantity of wa- 
ter. I added martial vitriol undissolved, and employed 
unboiled linseed oil. 
For want of a sufficient quantity of raw pulp, I pro- 
cured, for some experiments, fragments of coarse old pa- 
per and bookbinders* shavings, which, after being boiled 
for about three hours, were much tenderer than that 
brought from the paper manufactory. A pound of this 
when wet, after it had been pressed, exceeded that which 
was dry by about two thirds. 
The pulp procured from a paper manufactory being 
mixed in a mortar with the dissolved gluten, and being 
afterwards formed into a paste by the addition of the 
above earths and sulphat of iron, was well beat up in the 
mortar, and linseed oil then poured over it. The mass, 
being prepared in this manner, was spread out with a 
spatula above a sheet of coarse paper placed on a board 
furnished with a rim or border; another sheet of the same 
