A correspondent of the London Mechanics' Magazine informs that journal that in the arsenal of Brest, and elsewhere in France, a process is extensively adopted, which consists in the employment of certain salts of zinc, together with the oxyd of the same metal, and a substance designated as a retarding agent, as a vehicle or medium for pigments. This retarding agent appears to be borax, or the carbonate of soda, one of which substances is added to the zinc salts in solution previously to its being mixed with the oxyd. The salts mentioned are the chloride and sulphate of zinc. The proportion of the " retarding agent" is not well ascertained, but the proportion of the salt to the oxyd is that of their chemical equivalents. Although at first sight these facts seem to be, chemically, absurd, yet it is confidently asserted that this compound affords a paint as permanent as oil paint, at a fraction of its cost. This is a valuable discovery ; and if we can procure, by the unison of chemical substances, colors that will stand the weather without the medium of oil or varnish, it will be a great contribution to our accumulation of facts.