PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 417 



American Institute, Polytechnic Association, 7 



Sept. 26, 1861. S 



This being the day appointed by the President for a National 

 Fast, the Association adjourned to Wednesday next at half past 

 seven o'clock. 



American Institute, Polytechnic Association, 



Oct. 2, 1861. 

 Prof. C^a'us Mason in the chair. 



COAL TAR. ORIGIN OF COAL. 



Prof. Seely. — Coal tar is a most offensive substance to smell or 

 to tight, but it is very valuable notwithstanding. We are, 

 indeed, only beginning to learn some of its wonderful virtues. 

 For instance, some of the most gorgeous colors worn by fashion- 

 able ladies are produced from coal tar. I have twenty-five or 

 thirty samples of velvets colored by these dyes. The colors are 

 all brilliant. We have from it the simple colors of the spectrum, 

 reds, blues and yellows, and by their combination we may pro- 

 duce all other tints that are known, A few years ago coal tar 

 was little used except for preserving wood and it is still very exten- 

 sively employed in Europe for that purpose. They scarcely think 

 of laying a railroad sleeper which has not been cured in what is 

 called " dead oil," a product derived from coal tar. There are 

 about fifty different and peculiar substances which can be sepa- 

 rated from coal tar, some of which are very valuable. These 

 substances do not exist in the coal itself. That seems to be a 

 homogeneous compound, all the elements united into one sub- 

 stance, as sugar or as salt is one substance. But by heat the 

 coal is broken up into these compounds. Coal tar is only a sec- 

 ondary product; that is, we heat the coal,*not to obtain coal tar 

 but to obtain gas; and the coal tar which is produced has been 

 considered one of the greatest nuisances attending the carrying on 

 of the gas manufacturing business. It was considered so great a 

 nuisance in Philadelphia, that a remonstrance was extensively 

 signed, representing that it would breed pestilence in the air, and 

 poison the water and the fishes ; even the present director of the 

 Philadelphia gas works was one of the signers of that remon- 

 strance. It was then emptied into the river to get rid of it. 



The different products of which I have spoken, are generated 

 in the coal tar by the action of heat. Some of the nitrogen of 

 [Am. Inst.] AA 



