Tar Macadam 
43 
known in Germany as kleinpflaster and in Liverpool as random setts, is, in our 
opinion well worthy of careful consideration ' by road authorities. It was 
alluded to more than once in the course of the evidence by the principal road 
experts we had before us, who had themselves examined it, and it was always 
characterised as a most effective form of strengthening existing roads up to 
the standard of real efficiency for the carrying of heavy traffic. The method 
of laying it in Germany and the cost of labour and material are given in detail 
in Captain Bigham’s Eeport on Roads. 
“To meet the cases of towns and villages traversed by dusty main roads, 
some adaptation of the French tarring process has been suggested, and details 
of the method used and the cost are given in Captain Bigham’s Report. 
Although such a system would be too expensive for application on all main 
roads, involving, as we are told it would, an annual cost of from 40 1. to 50 l. 
a mile for an 18-ft. road, yet if applied in such localities only as we have 
mentioned the price might not be thought too great for such an effective 
remedy. Road authorities in several parts of England have experimented 
on short lengths with tar, tar-mac (a road material composed of iron slag 
broken small and boiled in tar), Westrumite, and other dust preventives ; but 
these experiments have not been on a sufficiently large scale or carried on long 
enough to afford any satisfactory information as to their success or cost.” 
Tarring, Tar Macadam, &c. 
Tar macadam has been used from time to time in the 
British Islands for many years, and the use of tar applied to 
the surface of paths and roads, which the Commission calls 
the French tarring process, was practised by some English 
surveyors long ago. The Report of Captain Bigham referred 
to is an admirable one, and in it the cost of kleinpflaster is 
given at 4s. 9 d. a square yard when laid on an old macadam 
road, and 7s. when laid on what is usually known as a Telford 
foundation seven inches deep, first overlaid by three inches 
of small broken stone. The total cost for a mile of new road 
eighteen feet wide would therefore be 3,663Z., and for armouring 
an old road 2,529 1. This cost per mile appears to be quite 
within the resources of urban authorities, and it would not be 
extravagant to use armoured macadam on some rural main 
roads, as the reduced cost for maintenance and cleansing would 
meet, to a great extent if not entirely, the interest and sinking 
fund on the cost of the improvement. 
The only other material for the cheap construction of road 
crusts, suitable to the needs of the present time on main roads, 
is tar macadam, of which tar-mac may be considered as a 
special variety, with some advantages due to the porosity of 
the slag, but somewhat likely to wear irregularly on account 
of want of uniformity in strength. Tar macadam can in some 
localities be laid four inches thick for about 2s. per square 
yard, but the cost per square yard for laying it, in 1905, six 
inches thick on the Victoria Embankment, where the results 
were not altogether satisfactory, is stated at from 4s. 6(7. to 5s. 3 d. 
per square yard by the Engineer to the London County Council. 
There are two serious difficulties in connection with tar 
