STREETMAKING.

New Zealand Mail, Issue 934, 24 January 1890, Page 22

STREETMAKING.

It is a notable but not a pleasing feature of the Wellington streets that most of the carriage-

roads, if not all, present a series of slight but irritating irregularities. Their surface is diversified by little hillocks alternating with small hollows. Over the elevations the wheels of vehicles jolt distressingly. The de--1 pressions become a chain of young j ponds after every shower, whether it I fall from the clouds or from the Corj poration water-carts. On the broadest parts of Lambton-quay, our chief city J thoroughfare, these characteristics are i specially conspicuous. Many people must have wondered what peculiarity in the construction of tho streets has brought about this very disagreeable quality of perpetual irregularity. An inspection of the method employed m the formation of the newer streets on the reclaimed land suggests speculation whether tho older thoroughfares were formed in the same way, aud whether, if so, this may not account for the remarkable diversification of their surfaces with undesired hills and dales. The course adopted in the more recent oases appears to be to lay down best a substratum of large pieces of stones irregular in shape, but fitted together its compactly as is practicable, and ■ o place over ‘this a stratum of small j met*!, i he whole being then con- ! -oiui J. J b 7 the passage of tbs steam ! f< ,j. The theory, no doubt, is that s -j i. ; r, ’ way a solid substructure is

placed above the clay soil, and that the smaller metal above' when pressed down by the heavy roller will fill all interstices, the whole thus becoming compacted into a solid mass. This plan, however plausible in appearance, is nevertheless a reversion to the obsolete system of road - making which prevailed before the days of Macadam, and which that great Road Reformer improved off the face of tho earth so far as Great Britain is concerned. The system which John Loudon Macadam introduced in 1815, at Bristol in the first instance, and which gave a new verb—- ‘ to macadamize ” —- to lhe English language, is based on a diametrically opposite principle. Macadam, writing on this subject, explains that the substructure of large irregular stones, however plausible in theory, is vicious in practice, because it involves tho formation of a series of minute but solid peaks, around which the superincumbent small broken metal gradually works down, thus leaving a series of alternate elevations and depressions as we see them iu some of our streets. His plan (as officially described) “ coneists in forming the roads out of hard materials, such a 3 granite, whinsto ie, and basalt broken into pieces, none of which are too large to pass through an iron ring 2|ln in diameter, and then deposited evenly in a bed of from Gin to 12in in thickness. The bed thus laid becomes perfectly compact and smooth ; and in proportion as if is worn away or cut into ruts by traffic, can easily be restored by a new coating of materials.” Later the diameter of the gauge-ring was reduced in many instances to two iuebes, as it was found that stone broken to this smaller size gave a more compact and homogeneous road. Apparently our own road making is carried out on the lines which went out of practice in England 75 years ago, aud the modern system which came in with Macadam is ignored. It seems to be feared that if the smaller stories were deposited directly upon the clay they would sink in and be swallowed up. This, however, is declared by engineering authorities to bean error, the macadamized road, if properly made and rolled, being less apt to sink than a road made after the older fashion. Ic may be worth while for the City Council to look into this matter, and ascertain whether the very patent defects in our streets may not be due rather to an injudicious mode of construction than to faulty material, and whether these defects might not be mitigated by resorting to Macadam’s method, which has found such marked favour in the Mother Country during tbe past three quarters of a century.