HALIFAX WATER WORKS. JOHNSTON. 103 



coating process of Dr. Angus Smith, which was first introduced 

 in the United States in 1858. The weight of experience seems 

 to show that in unco'ated pipes the first ten; or twelve years of 

 their life results in more or less rapid corrosion. After they 

 have become thoroughly tuberculated very slight changes take 

 place. If this is removed by scraping or c-leani'ng it begins to 

 form again, and the life of the uncoated pipe becomes much 

 reduced. 



The interior of coated *pipes become tuberculated in the 

 same way, due to a large extent to defects in the coating, but 

 very much less quickly, a ( nd when removed by scraping the 

 iron is uninjured. The writer was present recently when a 

 piece of pipe was cut out of the 15-inch main, and when the 

 deposit was rubbed off the coating was as sound and good as 

 when first put on. The outside of the pirpe was also in good 

 condition. The pipe had been cleaned a year previous, and 

 the tubercules had not begun to form, but there was a slight 

 deposit over the face of the pipe. The following points should 

 be observed in coating cast-iron water pipes : 



That the ovens in which the pipes are heated before being 

 dipped in the coal tar bath shall be so arranged that all portions 

 of the pipes shall be heated to an even temperature. 



The pipes should be heated to a temperature of 300 F. 

 before being dipped. 



The varnish to be heated to a temperature of not more than 

 300 F., and kept at this while the castings are in the bath. 



The pipes should 'not be submerged for less than five min- 

 utes, and when taken from the bath should be evenly coated. 



Joints. 



There are three kinds of joints in use in the water system, 



lead, wood, a'nd turned and bored. These latter joints have 



been in use since 1890, but they do not seem to find favor with 



engineers in America and are very little used in Canada or the 



United States ; although in the Metropolitan Water Works of 



