. Science of railways . eratethat the valve rises when it opensto a greater height than is usualin valves of this character. For tension of the spring andthe adjustment of the parts,means are conveniently ar-ranged and provided. A leveris furnished when desired. Insize and utility it is believed toafford all the advantages whichare demanded, and to meet allthe requirements of an exactingrailroad service. Directions.—It should neverbe nieddled with unless it be-comes necessary to reset it. In such case, firstloosen or remove the acorn check nut {K) above thespring bolt {F); then holding with a
. Science of railways . eratethat the valve rises when it opensto a greater height than is usualin valves of this character. For tension of the spring andthe adjustment of the parts,means are conveniently ar-ranged and provided. A leveris furnished when desired. Insize and utility it is believed toafford all the advantages whichare demanded, and to meet allthe requirements of an exactingrailroad service. Directions.—It should neverbe nieddled with unless it be-comes necessary to reset it. In such case, firstloosen or remove the acorn check nut {K) above thespring bolt {F); then holding with a wrench the hex-agonal top [B) of the valve, with another wrench turnthe nut (J) downward to increase, and upward toreduce the pressure, until the valve opens at thedesired point as indicated by the steam gauge. Tomodify the loss of pressure in blowing, slightly with-draw the screw bolt (M) in the base of the valve untilit ceases to engage with the ring (L) encircling thevalve seat (C), then with any pointed instrument. Fig. 6. Meady Muffled Locomotive Pop Safety Valve. LOCOMOTIVE APPLIANCES. 231 inserted into the small opening (TV) near the screwbolt, turn the ring (L) downward for diminishing, andupward for increasing the loss. CROSBY LOCOMOTIVE POP VALVES. Fig. 7 shows in section a Crosby plain popsafety valve. The valve proper {B B) rests upontwo flat annular seats (T^^ V) and (W W) on the sameplane, and is held down against the pressure of steamby the steel spiral spring {S). The tension of thisspring is increased by screwing down the threaded bolt(L) at the top of the cyhnder [K). The area containedbetween the seats (W) and (V) is what the steam pres-sure acts upon ordinarily to overcome the resistanceof the spring. The area contained within the smallerseat (IV TT ) is not acted upon until the valve larger seat {V V) is formedon the upper edge of the shell or body{A) of the valve. The smaller seat(W W) is formed on the upperedge of a cylindrical chamber orwell
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