Inks which are recommended as permanent, because water will not remove them, while it does immediately obliterate others, may not be permanent as against time. These inks may be the best for monetary purposes, but, owing to an excess of acid in them, may be dangerous in time to the paper. It is interesting, since coal tar has acquired so important a position in the arts, to trace how its various products successively rose in value. The prices in Paris, as given by M. Parisal in 1861, are as follows: Coal,.................................. 1/4 c. per lb. Coal tar,.............................. 3/4 " " Heavy coal oil,.............. 2 1/2 a 3 3/4 " " Light coal oil,............. 6 3/4 a 10 1 /4 " " Benzole,........................ 10 1/2 a 13 " " Crude nitro-benzole,................ 57 a 61 " " Rectified nitro-benzole,............ 82 a 96 " " Ordinary aniline,............. $3.27 a $4.90 " " Liquid aniline violet,.............. 28 a 41 " " Carmine aniline violet,....... 32 c. a $1.92 " Pure aniline violet, in powder,.... $245 a $326.88 " The last is equal to the price of gold. And so, says M. Parisal, from coal, carried to its tenth power, we have gold; the diamond is to come. Modern chemistry offers many formulas and methods of rendering visible secret or sympathetic inks. Writing made with any of the following solutions, and permitted to dry, is invisible. Treatment by the means cited will render them visible. Solution. After treatment. Color produced. Acetate of lead. Sulphuret of potassiurin. Brown. Gold in nitrohydroChloric acid. Tin in same acid. Purple. Nut-galls. Sulphate of iron. Black. Dilute sulphuric acid. Heat. Black. Cobalt in dilute Heat. Green. nitrohydrochloric acid. Lemon juice. Heat. Brown. Oxide of copper in Heat. Blue. acetic acid and salt Nitrate of bismuth. Infusions of Nutgalls. Brown. Common starch. Iodine in alcohol. Purple. Colorless iodine. Chloride of lime. Brown. Phenolphtalin. Alkaline solution. Red. Vanadium. Pyrogallic acid. Purple. The Patent Office at Washington, D. C., for more than forty years employed a violet copying ink made of logwood. From 1853 until 1878 it was furnished by the Antoines of Paris, of the brand termed "Imperial;" in later years it was supplied by the Fabers. Since 1896 they have been using "combined" writing fluids. The following facts elicited by the unrollment of a mummy at Bristol, England, in 1853, were communicated to the Philosophical Magazine, by Dr. Herapath. He says: