ASPHALTUM FOR A MODERN STREET. 



237 



of these constituents are not always present and vary widely in amount 

 when present, so that, from a chemical standpoint, the different asphal- 

 tums and the bitumens of the different asphaltes are very unlike sub- 

 stances. In the practical uses to which these substances are applied, the 

 selection for any given purpose does not appear to depend upon differ- 

 ence of composition. The purest varieties are used for making fine 

 varnishes and lacquers. Others are used for coarser varnishes that are 

 baked on to iron and other surfaces. Others are applied, softened with 

 solvents that evaporate. These substances find wide uses for insulating 

 purposes, alone and in mixture with other materials. 



The widest use to which they are applied is in street-paving sur- 

 faces, for which purpose vast quantities are used every year. It has been 



Fig. 9. Shaft on Asphaltum Vein near Asphalto, from which mass was taken 



weighing 6,500 Pounds. 



found in practice that good streets and poor streets have been made 

 from nearly all the different varieties of asphaltums and asphaltes that 

 can be obtained in such quantity and at such a price as to render their 

 use possible. The different results obtained appear to be due to causes 

 external to the asphaltum or asphalte employed, such as the kind and 

 quality of the materials with which they are mixed and the method, or 

 lack of method, by which they are mixed. These conclusions appear 

 to be warranted by a large number of experiments extending over many 

 years, some of which have been very expensive for the municipalities 

 making them. 



