PAPER-CCTTINa MACHINE. S8l 



The mimmiim nitrat, concentrated in a retort, grows Minim, nitrat 

 thick, gives out a little nitrous gas, enters into fusion, j^" ^^^ *"^ 

 and aflords a yellow sublimate that lines the sides of the 

 retort. The maximum nitrat aft'ords nothing similar to 

 this. If the melted mass be dissoWed, we see a yellowish 

 precipitate, mixed with a little powder of silver, fall to 

 the bottom ; which indicates, that a part of the minimum 

 nitrat remains unaltered, and that another portion has 

 assumed the maximum state, by means of the oxigen at- 

 tracted from part of the oxide. 



Several years ago I remarked this transmission of axi- 

 gen from one portion of an oxide to another, in those 

 solutions of silver in which I had carried the ebullition on 

 metal pretty far. A kind of brilliant aventurine dis- 

 turbed its transparency at the expiration of a few days, 

 .and afterwards subsided to the bottom of the vessels. 

 This was the first fact that led me to suspect, that silver, 

 ,.like so many other metals, was susceptible of two deter- 

 minate states of oxidation. 



Nitrat of lead treated with leaves of this metal exhibits Nitrat of lead 

 results of the same class. I will endeavour soon to lay ^^j^^J^ ""^^ *^' 

 them before the public. 



VI. 



Description of a Machine for cutting Paper and the Edges 

 of Books, Bi/ Mr. John J. Hawkins *. 



JL HE object of this improvement is, to cut the edges of Machine for 

 books on three sides at one fixing in the press : to do this, cutting the 

 it is necessary that the book be placed at one end, and a ^|^ ® ^® ** 

 support given to the plough beyond the part cut ; there 

 is therefore at each corner a block moveable on a centre, 

 so as to elongate alternately the side or end of the press. 



The press is as wide as the intended length of the 

 book. 



. * Communicated to the Society of Arts, who voted the Silver 

 Medal to the inventor. 



Vol. XV.— Supplement. FfC At 



