Y. N. S., West Newton, Mass., writes:

"A peculiar case of obstruction of a 4-inch vent pipe was brought to my notice to day. It was novel to me and may be of interest to others of your readers. According to the rules of the Board of Health, a soil pipe in the City Hall was extended full size (4 inches) through the roof several years ago. In order to get around roof timbers the stack was carried horizontally for a few feet under the roof, then by a quarter-turn was passed through the roof by a hub into which the flashing was turned, and a 3-foot length of pipe calked in the arrangement being shown by the accompanying sketch. Recently this piece A rusted off and fell over into the snow guard. When the plumbers went up to replace it, they found the section of pipe B passing through the roof cracked, and in removing it found the quarter-bend C at the bottom entirely closed with rust. The horizontal section D laid over some ceiling joists, and from appearances may have had a slight fall towards the rusted elbow, but certainly not sufficient to hold much water. It would seem as if the small amount of rain that from time to time fell in the open end caused the rust to start, and as there was never any flow to carry it off or scour the pipe, it gradually accumulated till it closed the pipe. This winter snow accumulated, melted, and finally the water thus formed froze and cracked the pipe.

" This shows the great objection to any horizontal runs, especially above fixtures on a soil pipe where there will be no flushing, and that especially near the roof outlet where direct run is not practicable, one-eighth bend should be used."

[Such stoppage from accumulations of scale rust are frequent in badly planned work in both vent pipes and extensions of soil and waste lines above the highest fixture connections. But it can be entirely prevented by following the New York regulations on this point that all such pipes where offsets are required must be run at an angle not greater than 45 degrees with the vertical, or in other words, one-eighth bends must be used instead of one-quarter bends. At this angle the scale rust will slide down and be washed away. It seems difficult to make some workmen comprehend that a vent pipe through which no water runs ought to have a much greater pitch than is necessary for waste pipes. There is no excuse for this defect in modern work, and such arrangements of piping have not been permitted in New York for some years. The work described was certainly not " according to Board of Health rules," as we know them.]