PROCEEDINGS OF SECTION H. 653 



Up to nearly the end of the eighteenth century the Roman system 

 of broken-stone pavements was adopted for the best work ; but subse- 

 quently several modifications were introduced, culminating in the 

 universal adoption more or less in its entirety of the method instituted 

 by Macadam. 



In concluding this historical introduction it will, therefore, be 

 proper to advert to the times of Tresaguet, the great French road 

 engineer, and Macadam and Telford, the illustrious English engineers, to 

 whose genius the early conceptions and inauguration of our present 

 system is due. Macadam pavements, on account of their low first cost, 

 are everywhere the most general form of road-construction now in vogue. 



The systems practised by the Romans may have produced an 

 equally good road surface, at any rate for their purposes, yet they 

 were extremely costly ; and it remained for John Loudon Macadam 

 to devise a systematic and rational method of constructing broken 

 stone pavements in a thoroughly scientific manner, so as to entail a 

 minimum of expenditure. 



In 1775 M. Tresaguet adopted a system of road- making very similar 

 to that devised by Telford 25 years later. Prior to 1775 the broken 

 stone pavements of France had been made after the Roman fashion, 

 according to which the ground was excavated level to a depth of about 

 2ft., then largish stones were laid on flat in three layers to form a 

 foundation ; on these small stones were laid and beaten down, and on 

 top of these a course of smaller stones was laid and beaten down 

 firmly. Tresaguet altered this by excavating the ground to a depth 

 of about 1ft., with the bottom curved the same as the finished surface, 

 then stone pitchers were laid edgewise by hand and beaten to an even 

 surface and finished off as before. 



In 1784 Macadam was appointed a road trustee and manager of a 

 district in Ayrshire, where he practised the method of road-making 

 which still retains his name. His system consisted of spreading 2in. 

 stones wherever possible on — not below, as in the case of Tresaguet and 

 all others — the properly levelled and drained road surface to a depth 

 of lOin., and the convexity given was only sufficient to properly shed 

 the rainwater readily to the side drains. In 1815 he was appointed 

 surveyor of roads in Bristol, where he metamorphosed some 178 miles 

 of roadway. By his system local finances, previously embarrassed, were 

 placed on a sound basis. So marvellous were the results obtained that 

 other authorities consulted him with equal success. The road trustees of 

 the Carse of Gowrie turnpike road in Perthshire became almost insolvent 

 owing to the cost of maintenance. They secured the advice of Macadam 

 and remade their roads accordingly, and their funds were soon restored 

 to a financial position. In 1850 Macadam's system was adopted through- 

 out France, perhaps the greatest compliment he could have had. 



In 1802 Thomas Telford undertook his first great piece of work 

 in the Highlands of Scotland, involving the expenditure of £450,000 

 and embracing 920 miles of road. According to his system the forma- 

 tion was levelled as in the case of Macadam, or excavated as in the case 

 of Tresaguet, but still with flat bottom, then pitchers were hand-packed 

 across the surface with base down and standing 7in. high in the centre 



