970 Transactions of the American Institute. 



three-fourths of an inch in diameter ; and even with that allowance 

 for error, the use of " that steel drift pin " is very frequently required. 



To the improvement which will he effected in the strength and 

 durability of boilers by adopting the modes of working described in 

 the foregoing extract, the writer's experience enables him to bear 

 unqualified testimony ; and the importance of their introduction into 

 American boiler shops cannot be too strongly urged, especially if the 

 practice of working engines on board passenger boats with steam of 

 twenty to fifty pounds' pressure per square inch is to be continued. 



That boilers, made in the manner described above, would be more 

 costly than such as m ay be made from plates picked up at random 

 in the market, their quality subjected to no reliable test, and the 

 workmanship bestowed upon their construction rude and imperfect, 

 is unquestionably true ; it is also true that they would not only be much 

 safer while in use, but would probably be so much more durable as to 

 be found, in the end, the cheapest. 



The writer has only to remark, in conclusion, that age and its 

 attendant infirmities compelled him, years ago, to retire from busi- 

 ness ; and that he has no interest, direct or indirect, in any work where 

 steam engines or boilers are manufactured. He presents this paper 

 for the single purpose of adding his mite to the general fund of infor- 

 mation, which ought to be made sufficient to enable all interested in 

 steam boilers, on shore or afloat, to form tolerably correct opinions 

 respecting their fitness for the work to which they are applied. 



Aniline Colors. 

 By Prof. C. F. Chandler. 



Illustrated by specimens of the colors, and of articles dyed with them. 



It is well understood that coal is an element of our national wealth, 

 and that we derive from it our power. The combustion of 300 

 pounds of coal under a steam-boiler will produce a power equal to 

 the mechanical force exerted by a man for a year. Another impor- 

 tant application of bituminous coal is to the manufacture of 

 illuminating gas. In this manufacture there are certain residual pro- 

 ducts, which were at first thrown away; and it is of these that I 

 propose to speak to-night. 



Coal tar is produced at the rate of about ten gallons to the ton of 

 coal. Thousands upon thousands of barrels of coal tar were at first 

 thrown away ; but when the chemist turned his attention to this sub- 

 stance, he discovered so many products useful in the arts which could 

 be made from it, that coal tar now finds a ready market at $1.50 per 



