15 



appearance. The whitening and cleaning up of the picture by this 

 process, is far more beautiful than by the ordinary method of fixa- 

 tion by a deposit of gold. A small portrait fixed in this way, more 

 than a year since, remains unchanged, and continues to be the 

 admiration of persons interested in this art. One remarkable 

 effect produced by this mode of fixing, is the great hardening of 

 the surface, so that the impression is effaced with great difficulty. 

 I have kept a small portrait, thus treated, unsealed and uncovered 

 for over a year, and have frequently exposed it in various ways, and 

 rubbed it smartly with a tuft of cotton, without apparently injuring 

 it ; in fact, the oxidised surface is as little liable to change as the 

 surface of gold, and is much harder. 



To succeed well in this process, the impression should be 

 carried as far as possible without solarization, the solution of the 

 hyposulphite of soda should be pure, and free from the traces f t' 

 sulphur, the plate should be carefully washed with distilled water, 

 both before and after it receives the deposit of copper, in fact, the 

 whole experiment should be neatly performed, to prevent what the 

 French significantly call taches upon the plate, when the copper 

 comes to be oxidized. 



The formula for the Daguerreotype process, which has now 

 been given, will, we trust, enable the amateur to pursue his 

 experiments with confidence and success. He will probably ex- 

 perience some disappointments, however carefully he may attend 

 to the rules which have been laid down, for there are few among 

 even the ablest experimenters who do not occasionally fail ; yet his 

 perseverance will often be rewarded by an excellent picture, when 

 perhaps, he least expects it. 



To obviate as much as possible these annoying failures, he should 

 bear in mind the following Cautions, by which he may ofttimes 

 discover the causes which prevent his success : 



CAUTIONS. 



1st. Never use the same accelerating liquid more than once or 

 twice, and only at short intervals. It is better to throw it away 

 after preparing such plates as can be prepared at the same time. 



2nd. Be sure to replace the plate on the accelerating liquid tor 

 a moment or two after having observed the colour, and before 

 putting it in the camera. 



3rd. Wipe the lens, and remove all dust and dampness from the 

 camera before using. 



4th. Keep the camera and mercury box perfectly free from the 

 vapour of iodine, bromine, etc. 



