PAVING COMPOSITIONS. 169 



— Canada, Sweden, and Eussia — that a low steel, with J to -| per cent, 

 phosphorus, was affected by cold much less than iron. According to Styffe, 

 there is no authentic case in which good steel contained more than 0.04 per 

 cent, of phosphorus ; though in one English iron rail there was 0.25 per 

 cent., and in Dudley iron 0.35. 



"We draw the following conclusions from all the data at hand : (a.) Iron 

 and steel, which are entirely or nearly free from all foreign materials, have 

 neither their resistance to dead load nptably increased by cold, nor their re- 

 sistance to shock diminished, (b.) Certain elements, not exactly determin- 

 ed, but phosphorus certainly, very much diminish resistance to shock and 

 sudden change of stress, (c.) The question cannot be definitely settled un- 

 til the chemical constitution is determined. {d.) Statistics of results in 

 warm and cold latitudes, in summer and winter, after long frost, on days of 

 sudden intensity of cold, are required. 



The above has reference to the immediate influence of temperature. In 

 regard to the effect of repeated changes of temperature, Wohler conjectures 

 that frequent vibrations of molecules caused by heat, have the game effect 

 in destroying cohesion as vibrations caused by external forces. Data from 

 observation have not been obtained. Spangenberg, after examination of 

 the fracture surface, did not adopt this hypothesis. Bauschinger, after test- 

 ing boiler-iron, thought it possible that the strength of the plate was weak- 

 ened by long action of the fire. But this decides nothing as to the effect of 

 repeated influences. If Wohler's hypothesis is correct, we should recognize 

 in change of temperature a cause of destruction, not only of metals, but also 

 of all other solid bodies. And safety co-efficients would be of no avail, for 

 if we should make one beam twice as large as another, each half of the first 

 would be as much affected as the whole of the second. In any case, bridges 

 and buildings, which are subjected to only slight variations in temperature, 

 will certainly be more likely to fail from other causes. 



PAVING COMPOSITIONS. 



L. W. Sinsabaugh, of the United States Patent Office, has compiled a 

 most excellent digest of all patents granted for paving and roofing composi- 

 tions up to January 1, 1876. 



Scarce a week passes that inquiry is not made of us concerning some 

 new method of forming asphalt paving composition. For information of 

 such, we will republish the English and American patents granted for such 

 compounds for 1874-5. 



Eichardson, James P.; March 30, 1875; No. 161,550. Application filed 

 August 1, 1874.— Five pounds eopal-gum, 20 pounds asphaltum, and 40 gal- 

 lons coal-tar are thoroughly mixed and commingled by the aid of heat, 

 and when properly combined, broken stone, ashes, or equivalent material 

 is added to form a plastic mass. This is applied to the road while still hot, 

 and rolled heavily until perfectly solid. 



