Waterbury evening Democrat., 1895-05-13
RoADeyILDINe MATERIALS.
Not So Much Depends on the Rock Usc
 as the Manner of Its Use.

Not So Much Depends on the Rock Used
 as the Manner of Its Use.
 What kind of rock makes the best road metal? Road engineers generally seek the hardest rock they can find, and the principle is generally, but not al ways, a correct onc. The object to be sought is hard, smooth surface that will not grind or cut readily under wheels, so as to make dust or mud. It is sometimes said that afl rocks harden when exposed to weather. This is far from being true of all rocks, though it is true of some of them. Syenite, for example, decomposes when exposed, as do many other rocks which contain solu- ble constituents. It should, moreover, never be forgotten by those who under take 10 make good roads that the ar engagement of the materials is of as much importance as the materials them selves. Clemens Herschel, an authority on this subject. covers the case exactly when he says:
 A commong ravel sieve often con- stitutes the principal instrument whose judicious use will make good road out of q miserable string of ruts and cobbly elevations, It would be only necessary to sift out and separate the soil under the road to a sufficient depth into cob bleS, coarse gravel. fine gravel and sand; then replace them in the order named and with the proper thickness of layers each. Wet down and roll, and the re- suit will be good road. y
 Frldspar. When feldspar decays, or when it is finely powdered, it forms clay or kaolin. Now, every one knows that clay should not be used for top dressing for roads, for when dry it forms n fine dust, and when wet it forms mud, both of which are objectionable, both on their own accounts and because they mark the beginning of the destruction of the roadway.
 Shades For roadbuilding purposes the shades may be divided into two classes, clay shales and sandy Shales. The clay shades are entirely unfit fol such purposes; the sandy shaleA are the only ones that should be used for toI dressing. The reason for this is that sooner or later the rocks are crushed anC ground up, and that which is made o clay only forms a fine dust when dry and pasty, sticky mud when wet. Int areuaceous or sandy shales. on the othel hand. contain so much grit that they usually pack hard and make q firn l roadbed.
 LimestOnes. was former ly regarded RE one of the best rocks fo top dressing, and it has been exclusive ly used for such purposes. It has, how ever, proved very unsatisfactory in thu long run. and ill many parts of tn, | country the limestone macadamizeC roads ara being taken up and recon structed of moro satisfactory materials l The rock wears easily into an impalpa ble powder when dry and forms a stick! paste when wet. Hard limestone make an excellent roadbed, but should not b used for surface dressing.
 Sandstones As rule. sandstone not good roadmaking rock. but if road builders will observe the behavior 0 Sandstones of different varieties the will find that some of them make fairl good roadheds, while others will not This difference is due to the absence 0 presence of . binding material, and Il more specific directions can be suggest ed than that clean sandstone containin no binding materials, as lime, clay c iron, should not be used for surface met als-John C. Branner.