STATIONARY ENGINES.
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description, any portion of the top of the boiler can be uncoveredwith a shovel, andexamined at once.
For the purpose ofexperiment, steamblows at two placesin the boilers at Tet-tenhall were sufferedto remain unrepairedfor a couple of years,in order to test thevalue of this covering,and the result wasan entire absence ofcorrosive action onthe plates. In theopinion of Mr.Martenloam sand is muchpreferable for thispurpose to any othermaterial, providedthat it is protected bya roof or covering. Itis much cheaper thanfeit, brick, or sheetiron casing with airspace; and muchsuperior to furnaceashes, cinders, orriddlings, which areoften placed overboilers, as these sub-stances frequentlycontain acids andother chemical im-purities, which on be-ing brought in con-tact with waste steamact very injuriouslyon wrought iron.