May 6, 1909! 



NATURE 



293 



their weight and speed, and effect of wear and tear on 

 the roads ; nationalisation of the roads, and Exchequer 

 grants towards their maintenance ; the collection of 

 statistics and standardisation of these. 



There can be no doubt that a very considerable change 

 has come about in the requirements of roads since the 

 advent of the motor-car. After the. introduction of rail- 

 ways the main roads became very much neglected, and 

 little interest was taken in their condition, but now they 

 are more used than even in the old coaching days. Kor 

 the traction engine, the motor-car, or the steam trolley the 

 old methods of management are unsuitable, and the new 

 conditions require diHerent treatment. The greater part 

 of ihe roads in rural districts may be described as having 

 grown or developed, and have been built up by the use 

 of the metalling placed on the surface without any founda- 

 tion. This accounts for their unsuitableness for the rapid 

 and heavy traffic with which they have now to contend, and 

 for the excessive cost of maintenance. 



The old turnpike roads, which constitute the greater 

 part of the main roads now under the control of the 

 county or borough councils, have been, as a rule, well 

 made, and are under the management of qualified 

 engineers, and on these roads considerable attention has 

 been paid in the endeavour to adapt them to the altered 

 circumstances; but on the highways which are under the 

 management of rural district councils the case is different. 

 These rural councils, from a false idea of economy, make 

 use of perishable materials for repairing the roads, such as 

 limestone or gravel, because these can be procured in the 

 neighbourhood, and can be obtained at less price than 

 suitable road material brought from a distance. With the 

 same false idea of keeping down the cost, unqualified 

 men are employed as surveyors at small salaries. Some- 

 iimes the only qualification that the applicant for this ofifice 

 possesses is that he has been unsuccessful in his business 

 as a farmer. 



In a pamphlet on the repair and management of roads, 

 issued by the Roads Improvement Association for the use 

 of surveyors of highways, it is clearly shown that roads 

 well maintained and kept in good order cost less than bad 

 roads repaired with inferior material. .^n example is 

 given of a turnpike road which had been much neglected, 

 of which, owing to change of management and the use of 

 granite in place of local stone, the cost was not only con- 

 -siderably reduced, but from the improved surface of the 

 road one horse was able to draw as large a load as 

 ■formerly required double the number. In the same dis- 

 trict it was also shown that the parish roads, which cost 

 the most to maintain, were without exception those that 

 ^vere kept in the worst condition, and that when these 

 were placed under efficient supervision, while the roads 

 improved, the cost of their maintenance diminished. 



'ihe use of self-propelled vehicles, owing to the way in 

 which they affect the surface of the roads, more than ever 

 .emphasises the necessity for the use of skilled supervision. 

 There was a unanimous expression of opinion at the con- 

 ference that the cost of maintaining the roads had very 

 ^■onsiderably increased, and that in many cases, owing to 

 the want of proper foundations or inadequate metalling, 

 thf-y are quite unsuited for the class of trailic that they 

 have now. to bear. 



In one of the papers read at the congress it was shown 

 that to cover such roads with a coating of suitable material 

 of a thickness of 3 inches, in place of the flint or lime- 

 stone at present in use, would cost iioo!. per mile, or 

 five millions of pounds for the south-eastern division of 

 Kngland. where the motor traffic is the heaviest, and to 

 which the paper more particularly referred. 



The cost of maintaining the main roads has been very 

 largely increased owing to the wear- and tear of auto- 

 mobiles. During the last nine years the annual cost of 

 the main roads, which extend over- a length of 27,600 

 miles, has risen from 2,024,711/. to 2,766,003!., or at the 

 rate of 76-i(. to 100-2/. per mile. In one of the southern 

 rounties the cost has been doubled. . , 



.\ matter that received considerable attention at the con- 

 fereme was the nuisance due to the dust which prevails in 

 dry weather along the roads frequented by self-propelled 

 vehiili-s moving at great speed. Motor-cars not only rni>;e 

 and distribute dust in a m.Tnner previouslv unknown, but 



NO. 2062, VOL. 80] 



also are responsible for its production. , This is especially 

 the case on the roads that are in the worst state, of. re- 

 pair. On a loose surface the fine particles, which act as 

 a binding material to the larger stones, are sucked up 

 by. the tyres of the wheels and distributed over the road, 

 causing inequalities and providing material for dust. A 

 great deal of damage is also done by the sucking out of 

 the water from the puddles when the road is wet. A 

 rubber-tyred wheel splashing into a puddle sends the 

 water flying out of it with a speed and force greater 

 than any other vehicle, and converts a small puddle into 

 a larger one. This effect is greatest where the surface 

 is repaired with soft material, or where the material used 

 for binding is unsuitable. On roads under the manage- 

 ment of unskilled surveyors any material is considered 

 sufficient for binding the larger stones used for covering 

 the surface of the road. The scrapings of the mud off 

 the road in winter are often made use of for this purpose, 

 and in one of the papers read at the conference it is stated 

 that in one district even material was dug from the sides 

 of the road, and the metalling bedded with this. Under 

 such practices the result, of course, cannot be otherwise 

 than a muddy surface in winter and dust in dry weather. 



Various processes have been tried as a means for pre- 

 venting the generation of dust, but the one most generally 

 adopted in this country is to make the surface of the 

 roads waterproof by the use of pitch or tar, either as a 

 matrix for binding the stones together or as a surface 

 dressing. Already 1500 miles have been treated in this 

 way. The best results are obtained where there is a good 

 foundation, and a surface covering of suflficient thickness 

 of the hardest and toughest material, well consolidated by 

 rolling, with just sufficient fine chippings of the same 

 stone to fill the void spaces, the surface being rendered 

 impervious to water or the action of frost by the use of 

 tar or some bituminous material. Tar macadam, which 

 consists either of the whole material used or only 

 of the binding material being mixed with tar 

 before being placed on the road, has been largely used. 

 Opinions varied as to the use of this process. In some 

 cases it has been a complete success, in others a failure. 

 This is probably owing to the manner in which the 

 material has been prepared and laid, and to the quality 

 of the tar or pitch used. To be successful it requires that 

 the material must be mixed with the tar when it is dry, 

 and dry weather is required when it is put on the road. 

 If improperly mixed it either breaks up in patches, which 

 are difficult to repair, or becomes so soft in hot weather 

 as to work into a very uneven surface. 



For surface dressing on roads already made and in good 

 condition, spraying with tar either by hand or by a 

 machine made for the purpose is effective, and as it adds 

 considerably to the life of the road it does not add much 

 to the cost of maintenance. 



No reference was made in any of the papers to the 

 practice in use in the United States, and which now 

 extends over many hundreds of miles in California and 

 other States, of using petroleum or bituminous oil for 

 spraying instead of tar, which is there found to be_ very 

 effective. The oil is spread from a specially designed 

 tank-car at a rate varying from one to two gallons to 

 the square yard. Roads so treated are fit for traffic 

 twenty-four hours after being sprayed : they are thus 

 rendered impervious to rain-water, and the surface remains 

 hard and firm in hot weather. 



MAG}iETlC SVRVEYS> 

 "yilE first volume referred to below may be regarded 

 -'- as the coping-stone of the work done for the Coast 

 and Geodetic Survey by Dr. Bauer during his tenure of 

 the oflfice of chief of 'division of terrestrial magnetism. 

 Dr. Bauer had actually transferred his services to the 

 Carnegie Institution of Washington before the ■ volume 



1 Department nf Commerce and Labour, Cnast and Geodetic Survey, 

 United Stales Magnetic Tables and Masnstir Charts for 1905. By L. A. 

 Bauer. Pp. 154. (Washington : Government Printing Office, 1908.) 



Magnetic Survey of the Dutch East-Indies. 1903-7. By Dr. W. van 

 Bemmelen. Pp.69; with charts. fBatavia: Government Printing Office, 



Survey of India, Extracts from Narrative Reports, 1906-7. (Calcutta: 

 Superinltndent Government Printing, 1909.) 



