Annual report of the Boston Transit Commission, for the year ending .. . -sized stone passes into aGates stone-crusher, and is thence carried back into thegravel hopper by means of a belt carrying pockets. Anenlarged section of the screen is so arranged as to revolvein a tank of water, thus affording a means of thoroughlywashing the gravel. When the sand and gravel hoppers are full, the surplussand and gravel is carried on travelling belts to the cars atthe side of the trench, for removal as required. In this second machine is another hopper which can befilled with cement from the top. It is s
Annual report of the Boston Transit Commission, for the year ending .. . -sized stone passes into aGates stone-crusher, and is thence carried back into thegravel hopper by means of a belt carrying pockets. Anenlarged section of the screen is so arranged as to revolvein a tank of water, thus affording a means of thoroughlywashing the gravel. When the sand and gravel hoppers are full, the surplussand and gravel is carried on travelling belts to the cars atthe side of the trench, for removal as required. In this second machine is another hopper which can befilled with cement from the top. It is so arranged as tomeet the sand and gravel hoppers at the bottom of themachine, where all three are fitted with regulating can be so adjusted as to ensure a rate of deliveryfrom their respective hoppers equivalent to the proportionsof each material specified for the concrete masonry ; namely,1 part cement, 2^ parts sand, and 4 parts gravel. In thisway the proper amounts of material are emptied into arevolvino; concrete mixer underneath. Here the ingredients. wo H HI oz 2 »^ CO o CO HO z o o o t]0 o z o o HCO H?0
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Keywords: ., bookauthorbostonma, bookcentury1800, bookdecade1890, bookyear1895
