262 TOWERS AND TANKS FOR WATER- WORKS. 



While the preponderence of evidence is in favor of the use 

 of red lead in oil for protective coatings for iron and steel, 

 numerous failures are recorded, but as a comparison of evi- 

 dence might be continued ad infiiiitnin, such a task will not 

 be attempted here, further than to mention the results of a 

 series of tests, extending over two years, and made by Prof. 

 Sabin upon steel plates coated with a wide variety of paint 

 covering, the samples being afterwards immersed continuously 

 and subject for two years to the action of both salt and fresh 

 waters. Prof. Sabin's conclusions, represented in a paper 

 read before the Engineers' Club of Philadelphia, May, 

 1900, were that " the character of the pigment in a majority 

 of cases made very little difference : that oil-paints did not 

 withstand the action of the water as well as varnish-paints," 

 but that " red lead stood better than any of the oil-paints. 

 There is no question about it. It did not stand as well as 

 many varnish paints. It did not stand as well as some var- 

 nishes without any pigment in them." 



Structures are not as a rule subject to such action of the 

 water as took place in Prof. Sabin's experiments, and while 

 these were very carefully made and recorded, certain results 

 where metal plates were submerged would not necessarily 

 have a distinct bearing where a structure is subject only to 

 atmospheric influence; but in view of the fact that such struc- 

 tures as tanks, intermittently or continuously filled with water, 

 are the prime subject of consideration here, his experiments 

 are of considerable value. 



Asphaltic Varnish. Varnish differs from paint only in 

 the base the medium, linseed-oil, remaining the same. In 

 varnish, the pigment gives place to various resins, dissolved in 

 the spirits of turpentine, a volatile oil. These resins are of 

 vegetable origin, and are classed as "recent resins," the resin- 

 ous gum of a recent period, and " fossil resins," the volatili/< d 

 gums of trees long buried in the earth. Varnish resins are 



