n to the low- or if this plan prove costly, a second layer of gravel alone is sold separately ; but in making macadamized roads it is de- est practicable limit, at the least cost for construction and may be used. sirable to use the screening device. The machine is con- maintenance, They should be… … a brief consideration ble stones firm and in of their relative modes tact, andin preventing ficulty. The proper speed for these machines is about 200 the stones working up and destroying the surface. A remedy of construction, we may refer to a standard machine for the revolutions of the crank per…
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