450 NEW YORK STATE MUSEUM 



The most efficient and economical road metals are diabase or 

 trap and syenite. 



Granite and gneiss, especially if very micaceous, are apt to dis- 

 integrate rapidly and produce dust and mud. 



Shale is to be avoided, as it breaks up rapidly, forming a sticky 

 mud. 



Gravel, while making a serviceable road, will not pack well? 

 and is not durable. If it has to be used, some of the difficulty 

 may be overcome by cracking half of the pebbles. 



