352 Memoir upon the Causes of the long Duration 
or black-lead pencil, it fixes them firmly; and they may then be 
“washed over with any water colours, previously mixed with a 
portion of it, without in the least degree disturbing the chalks or 
black-lead. 
For miniature painting, being washed over the surface of the 
ivory, it completely removes its'greasiness; and being mixed with 
the colours, it causes them to float freely thereon, and tints may 
be laid over tints, the colours being struck into the ivory. 
For transparencies, oiled pdper, being first washed over with 
the refined ox gall, and permitted to dry, water colours, mixed 
with some of it, will lie freely, and perfectly smooth upon it, and | 
be so fixed, as not to wash up by the repetition of different 
glazings of colours, over each other; thus producing depth of 
colour. 
In short, the valuable properties this refined ox gall possesses, 
make it equally applicable to historical, landscape, botanical, 
and natural history painting, as well as to colouring prints in 
general ; and, by its readily combining with all the vehicles used 
in the preparation of water colours, and having no colour in it- 
self, it enables the artist to paint with ease on surtaces otherwise 
unfavourable, at the same time rendering the colours more bright 
and durable. 
Many other valuable properties will, no doubt, on trial, be 
found in this preparation ; and the result cannot fail to facilitate 
and improve the art of painting in water colours; and, as the 
discovery of it is entirely new, it will in all probability be found 
applicable to many other useful purposes. 
May 20, 1812. P. W. Tomkins. 
LXXV. Memoir upen the Causes of the long Duration of the 
Chinese Empire. Read to the Philotechnic Society, 2d of 
May 1813. By M. Pacaner, Member of several learned 
Societies *. 
Ix order to confine my subject within the bounds which cir- 
cumstances require, I shali rapidly run over the traits which 
characterize all the nations of antiquity, and which distinguish 
them from those of Europe. Passing afterwards from these 
general considerations to the particular character of the Chinese, 
it will be acknowledged that this ancient nation is not less di- 
stinct from those who occupy the opposite extremity of Asia, 
than the latter are from the Hungarians and Germais. 
Institutions in general derive their chief force from local con- 
veniences; that is to say, irom the concordance between those 
* Magazin Encyclopédique, 1813, tome iy. p, 88. 
institutions 
