106 NEW YORK STATE MUSEUM 



having the durability to support heavy traffic for a long time, can be 

 cheaply renewed if the source of supply is not far distant. This fact has 

 been recognized for a long time at points within easy reach of the lime- 

 stone quarries. In Onondaga county at many points a portable crusher 

 has been used to crush for road metal the blocks from the limestone 

 fences which are cheerfully donated by the residents for the improve- 

 ment of the roads. There are many other counties in which this might 

 be done as may be seen from the map which shows the distribution of 

 the limestone areas. In most of these areas limestone will be found in 

 the fences and may be crushed for road metal at small expense. 



The lists of quarrymen and the maps at the end of this bulletin explain 

 the distribution of materials available for road building. 



The distribution of road materials may also be studied in greater detail 

 on the Economic Map of New York by F. J. H. Merrill which shows 

 both the geology and the mineral deposits on a scale of 12 miles to 

 1 inch and on the Preliminary Geologic Map of New York by the State 

 Geologist which shows the geology on a scale of 5 miles to 1 inch.| 



In addition to the outcrops and ledges where quarries may be opened 

 the deposits of boulders and gravel whrch we call glacial drift often yield 

 good materials for road metal at a long distance fsom the original source. 

 These deposits cannot as yet be mapped but they are usually well known 

 in the regions where they occur. 



Tests of Road Material 



The most practical test of road metal is actual use, and this has been 

 the principal guide in the past ; but as the demand becomes greater for 

 new localities of road metal in order to reduce transportation charges, it 

 has become necessary to devise physical tests which may be used in the 

 examination of new materials offered for road building. 



The following description quoted from the report of the Massachusetts 

 Highway Commission for 1896, describes in detail the methods in use by 

 that organization.* t 



LABORATORY EXPERIMENTS ON ROADBUILDING STONES 



The following described results were obtained in the highway labora- 

 tory of the engineering department of the Lawrence Scientific School of 

 Harvard University. Those under the head 'Coefficient of abrasion' 

 were obtained by the Deval method, which has been employed for some 

 time by the French engineers for determining the relative value of the 



* Pp. 86-91. [. + In this quotation, metric weights and measures have been reduced to common 

 forms. 



t For Westchester Co. see A Geological [Map of a Part of Southeastern New York by F. J- H. 

 Merrill, in Bulletin 15, N. Y. State Museum; also in 48th Ann. Rept. N. Y. State Museum. 



