4. What colors for paint are best suited to different conditions.

5. Elasticity of paint coats.

6. Covering and spreading powers of paints.

7. Cement paints.

8. Linseed oil alone for the shop coat.

9. Climatic influences on paints.

10. Application of paint by spraying.

11. How best to prepare new metalwork to receive the shop coat.

12. Pickling.

13. How best to paint newly-erected metal.

14. Concrete encasement.

15. Gunite.

16. Proper treatment of steel that is to be encased in concrete or gunite.

17. Water-proofing.

18. Protection of metal against brine drippings.

19. Protection of metal against locomotive gases.

20. Causes of paint deterioration.

21. How to care for incipient failure of paint.

22. How to determine when repainting is necessary.

23. How to clean the metalwork preparatory to applying a new coat

of paint.

24. Application of paint after field cleaning.

25. Factors that affect results in painting.

26. Economic observations concerning painting in general.

The topics in the above list will be taken one at a time and discussed from the economic view-point.

Best Kinds of Paint for Shop and Field

Concerning the best kinds of paint for bridges there has been waged a lively war of competitors during half a century or longer, each one claiming that his product is the best. Independent engineers, too, have varied in their views thereon, for each one has been rather prone to be influenced by his own personal experience; but of late years a general consensus of opinions has been reached, the decision being that the priming or shop coat should be red-lead paint, the first field coat a mixture of red-lead and some so-called inert material, and the third coat a carbon or graphite paint. The term "inert" as applied to paint constituents was originated some thirty years ago by the late Dr. Dudley. It reflects his idea that lead and zinc pigments are chemically active towards linseed oil, while barytes,  silica,  etc.,  are  not.  As  a  matter of  fact,  the  most  important,  if  not  the  only,  relations  between  the  pigment  and  the  vehicle  are physical,  and  in  that  sense  there  are  no  inert  pigments.  Nothing  can  be  less  chem-