150 SECTIONAL ADDRESSES. 



problem of road surfaces is in a large measure one not only of the suitability 

 of materials to resist impacts but also of the prevention of impacts. An 

 old philosopher, Desagulier, as long ago as 1714, argued with a direct 

 simplicity worthy of a scientific man of eminence that a piece of glass 

 could be struck many small blows without fracture, but one large enough 

 would splinter it in pieces, and that a four-wheel waggon passing over a 

 horseshoe might strike such a small blow that little damage would be 

 done, whereas a two-wheeled waggon carrying the same load might 

 destroy the road surface quickly. The problem might be slightly 

 differently stated to-day, but in principle the difficulty is that suggested 

 rather quaintly by Desagulier. Many experiments of actual road surfaces 

 are being carried out in all parts of the civilised world, but considering 

 its economic importance, the cost of upkeep of roads and the inconvenience 

 of repeated repairs, it would appear that it would be well worth while, 

 even though there may be doubt as to whether any definite and final 

 conclusions can be reached in the laboratory, to let carefully but boldly 

 conceived laboratory experiments direct the large-scale experiments 

 much more than at present. If the history of other engineering develop- 

 ments is to repeat itself, only by such a procedure is the solution likely 

 to be found. In many branches of engineering, materials and precision 

 of finish have brought about remarkable developments and if, by close 

 control of processes, plane road surfaces that will reduce blows to a 

 minimum can be constructed of materials having a reasohable coefficient 

 of friction, a sufficient degree of resilience and abrasive resistance, real 

 advances may be expected. Steel, rubber and many other materials 

 have been suggested ; it may be that the chemist has by no means said 

 the last word on the possibility of synthetic substances that will fill the 

 bill, but, however that may be, whether in the direction of new materials 

 or in the better use of materials that are available, it seems clear that road- 

 making has become of such economic importance to the world that it 

 should be removed from the category of ' trial and error ' which for 

 centuries has been the method of advance, and all the aids that science can 

 give should be enlisted to achieve the desired end. It is not intended 

 to suggest that science is not at present assisting. The chemist is con- 

 trolling the manufacture of cements, so that products of great reliability 

 are available from the various firms manufacturing cements ; tars and 

 bitumen and other materials of a mastic character are determined in con- 

 sistency and properties by the control of physicists and chemists ; india- 

 rubber vulcanised under definite chemical control is being tested in road 

 surfaces ; certain substances like silicate of soda have been introduced as 

 dressings to concrete ; laboratory tests have been made in connection with 

 concrete and other materials, but in the field concrete is not by any means 

 made under that rigidity of control necessary for a product of known 

 properties to meet particular conditions ; it seems clear that many miles 

 of main roads have been made of concrete, suitable perhaps for some 

 purposes, but not of the mixture necessary to meet conditions of heavy 

 road traffic. But in the direction of research for new materials, as well 

 as in the control of the manufacture and of the properties of known 

 materials and in the actual carrying out of the work in the field, science 

 and the scientific method seem to be the necessary aids for future progress. 



