The following formulae are for use with gelatino-chloride paper or plates. The quantities are in each case calculated for one ounce, three parts of each of the following solutions being employed and added to one part of solution of protosulphate of iron. Strength, 140 grains to the ounce.

Slaty Blue.
1. - One part of the above solution to three parts of a solution of citrate of ammonia.
Greenish Brown.
2. - Citric acid.180grains
Carbonate of ammonia.50"
3. - Citrate of ammonia.250grains.
Chloride of sodium.2"
4. - Citrate of ammonia.250grains.
Chloride of sodium.4"
Sepia Brown.
5. - Citrate of ammonia.250grains.
Chloride of sodium.8"
Clear Red Brown.
6. - Citric acid.120grains.
Carbonate of magnesia.76"
Warm Gray Brown.
7. - Citric acid.120grains.
Carbonate of soda.205"
Deep Red Brown.
8. - Citric acid.120grains.
Carbonate of potash.117"
Green Blue.
9. - Citric acid.90grains.
Carbonate of soda.154"
Citrate of potash.24"
Oxalate of potash.6"
Sepia Red.
10. - Citric acid.80grains.
Carbonate of soda.135"
Citrate of potash.12"
Oxalate of potash.3"
11. - Citric acid.108grains.
Carbonate of magnesia.68"
Carbonate of potash.12"
Oxalate of potash.3"
Sepia Yellow.
12. - Citric acid.40grains.
Carbonate of magnesia.25"
Citrate of ammonia.166"
13. - Citric acid.120grains.
Carbonate of magnesia.72"
Carbonate of ammonia.72"
Chloride of sodium.8"
Blue Black.
14. - Citric acid.120grains.
Carbonate of ammonia.70"
Carbonate of magnesia.15"
15. - Citric acid.120grains.
Carbonate of magnesia.38"
Carbonate of ammonia.44"
16. - Citric acid.90grains.
Carbonate of magnesia.57"
Citrate of potash.54"
Oxlate of potash.18"
17. - Citric acid.72grains.
Carbonate of magnesia.45"
Citrate of potash.54"
Oxalate of potash.18"
18. - Citric acid.60grains.
Carbonate of magnesia.38"
Citrate of potash.68"
Oxalate of potash.22"
A more Intense Blue Black.
19. - Citric acid.30grains.
Carbonate of magnesia.18"
Citrate of potash.100"
Oxalate of potash.33"
A Clearer Blue.
20. - Citrate of potash.136grains.
Oxalate of potash.44"

In the photographic exhibition at Florence, the firm of Corvan1 places on view a frame containing twenty proofs produced by the foregoing twenty formulae, in such a way that the observer can compare the value of each tone and select that which pleases him best. - Le Moniteur de la Photographie, translated by British Jour. of Photo.

[1]

Does this mean Mr. A. Cowan? - Translator.