^3 
wpm Copper in Alto Relievo. 
be done with It, if proper materials can be found out to work 
with. It possesses every advantage which common engraving 
does, and at the same time all the advantages of engraving on 
wood ; and, above all, it enables us to procure as many impres- 
sions as can be taken from types The greatest difficulty to 
be surmounted, is to obtain a substitute for the varnish, which 
will flow from a pen or pencil like Indian ink ; for as the var- 
nish has a tendency to dry, and get tough in the pencil, the 
operation is by this circumstance very considerably impeded. 
Other substances than copper may be used ; and experience 
may prove them to be better adapted to the purpose. I have 
tried wood covered with white lead and strong glue, with con- 
siderable success, but not with so much as copper ; and it may 
be as well, for the sake of those who may think it worth their 
while to make other trials, to mention, that I have used lead, 
pewter, type-metal, zinc, and brass, all with various success, but 
have still found copper superior to them all. Mr Sivright of 
Meggetland, a gentleman well known in this city for his scien- 
tific acquirements, and to whom, during these experiments, I 
was much indebted, used with very great success the same kind 
of limestone which is employed in lithography. 
I have also tried various kinds of varnishes, viz. mastic var- 
nish, japan, liquid etching-ground, copal varnish, and spirit var- 
nish, but have found the best to be common turpentine varnish, 
or resin dissolved in turpentine. 
Edinburgh, October 1819. 
Art. VI .— the Application of a new mode of Analysis to 
the theory and summation of certain extensive classes (f 
Series. By J. F.- W. Herschel, Esq. F. R. S., &c. Com- 
municated by the Author. 
-i- HE first idea of separating the symbols used in analysis, to 
denote the operations by which one function is derived from 
* I have not been able to find out the number of impressions which types 
will take, but I have been informed that an edition of 20,000 was printed from a 
-Gaelic Testament at the University Press here, and stereotype plates afterwards 
cast from the same types without any apparent diminution of their sharpness. 
