Aug. 1, 1865.] THE TECHNOLOGIST. 
ANIMAL SUBSTANCES USED FOR WRITING ON. 13 
While it is desirable that a more extensive knowledge should he 
obtained of the various gums yielded by the forest trees and plants of 
our colonies, attention should be strongly directed to the importance of 
extending and improving the preparation of caoutchouc in Demerara 
and Africa, as being likely to be attended with benefit in a commercial 
point of view. The numerous samples brought from the Upper 
Essequibo and Western Africa, although of fair value, indicate that the 
process of preparation admits of great improvement. 
ANIMAL SUBSTANCES USED FOR WRITING ON. 
Various forms of parchment and vellum, prepared from the skins of 
the sheep, goat, calf, and other animals, were not only much used in the 
times of the Romans, but continue to be used for legal and other docu- 
ments desired to be preserved in our own day. Parchment and vellum 
seem to have superseded papyrus about the seventh centiuy. A large 
proportion of our legal documents affecting heritable property is still 
written on vellum or parchment ; and strange to say, these are not made 
so well now as during the middle ages. 
Vellum and parchment were also used by the Jews for their sacred 
and legal writings, and the legal documents employed in their 
synagogues are still composed of them. But the material was expensive, 
and hence arose the practice of erasing the writings and reselling the 
vellum. Doubly used pieces of parchment were called " palimpsets ;" 
and about the fourteenth or fifteenth century, the restoration of old 
parchments had sprung into a regular trade. 
Sheets of gelatine are much used now for ornamental printing, for 
fancy labels, and silk is very often employed to print play-bills and 
newspapers on for special presentation. A strong kind of paper has 
come largely into use of late for various purposes, under the name of 
vegetable parchment. It is made by dipping for a few seconds ordi- 
nary-made paper into sulphuric acid, to which one part of water to six 
of acid has been added. The parchment is then taken out and 
thoroughly washed to remove all traces of the acid. Parchment thus 
made of paper is nearly as good as the old animal tissue, which it 
closely resembles in appearance, and much cheaper. 
A few other animal substances may be alluded to. We have long 
been accustomed to make notes on ivory pocket tablets. But now it is 
sought to utilise the shreds and clippings of ivory, which form a con- 
siderable waste in certain processes of turning, &c. These clippings 
contain some fibre, and it has been attempted to work them up into 
paper. An American Journal (these curious statements generally 
