12.--Citric acid. 40 grains.
Carbonate of magnesia. 25 "
Citrate of ammonia. 166 "

13.--Citric acid. 120 grains.
Carbonate of magnesia. 72 "
Carbonate of ammonia. 72 "
Chloride of sodium. 8 "

_Blue Black._
14.--Citric acid. 120 grains.
Carbonate of ammonia. 70 "
Carbonate of magnesia. 15 "

15.--Citric acid. 120 grains.
Carbonate of magnesia. 38 "
Carbonate of ammonia. 44 "

16.--Citric acid. 90 grains.
Carbonate of magnesia. 57 "
Citrate of potash. 54 "
Oxlate of potash. 18 "

17.--Citric acid. 72 grains.
Carbonate of magnesia. 45 "
Citrate of potash. 54 "
Oxalate of potash. 18 "

18.--Citric acid. 60 grains.
Carbonate of magnesia. 38 "
Citrate of potash. 68 "
Oxalate of potash. 22 "

_A more Intense Blue Black._
19.--Citric acid. 30 grains.
Carbonate of magnesia. 18 "
Citrate of potash. 100 "
Oxalate of potash. 33 "

_A Clearer Blue._
20.--Citrate of potash. 136 grains.
Oxalate of potash. 44 "

In the photographic exhibition at Florence, the firm of Corvan[1]
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._

[Footnote 1: Does this mean Mr. A. Cowan?--_Translator._]

* * * * *

NOTE ON THE CONSTRUCTION OF A DISTILLERY CHIMNEY.

At a recent meeting of the Industrial Society of Amiens, Mr. Schmidt,
engineer of the Steam Users' Association, read a paper in which he
described the process employed in the construction of a large chimney
of peculiar character for the Rocourt distillery, at St. Quentin.

[Illustration: FIG. 1--ELEVATION.]

This chimney, which is cylindrical in form, is 140 feet in height, and
has an internal diameter of 81/2 feet from base to sum