Eepoet on the Mines and Mining Exhibit. 339 



road metal. This material was exhibited because it was identical with 

 the trap of Kockland county. 



Farther up the Hudson river the limestone (juarries of Tompkins 

 Cove have been in operation for a number of years and supply large 

 quantities of rock for Macadam. It is one of the best materials used. 

 This magnesian limestone is hard and paclvs easily and makes a good 

 surface, but the cost of maintenance is considerable. The following is 

 an analysis : 



Lime 60 . 20 



Alumina 11 . 22 



SiHca 6 . 13 



Magnesia 10 . 45 



Carbonic acid 8 . 00 



Water 4.00 



100.00 



At lona Island a granite is quarried and broken in a Blake crusher 

 to five or six different sizes for road metal and concrete. The tine 

 residue, or dust, is sold, for polishing. Mr. Daniel E. Donovan, of 

 Kingston, N. Y., is the owner. 



The Hudson River Stone Supply Co. has an extensive plant for 

 quarrying and crushing granite at Breakneck Mountain, north of Cold 

 Spring. The same company operates a second plant for supplying 

 crushed limestone at Stoneco, north of ISTew Hamburg. 



One of the largest quarries in the State is that of P. Callanan at 

 South Bethlehem, Albany county. The lower Helderberg limestone 

 is the rock used and it makes a good road. At Howe's Cave the same 

 limestone is crushed for roadmaking. The Cauda-galli grit of Albany 

 county is used in small quantities locally and makes an excellent road, 

 though not very durable. 



At Port Chester, Westchester county, a coarse grained granite is 

 quarried and is considerably used locally, but the best Macadam roads 

 of that district are of limestone from Tompkins Cove. 



The gray gneiss has been considerably used as a road material in 

 Westchester county. 



On Staten Island the yellow gravel is much used for roadmaking. 



The materials used for making roads in the State vary with the 

 locality. If the traffic on the road is moderate it is generally safe to 

 use the local material, whatever its nature, unless it be shale, but if 

 there is a heavy traffic it will pay in most instances to get a stone of 

 superior quality from elsewhere. The requisite qualities of a road 

 metal are hardness and toughness. Where both these qualities are not 

 obtainable in the same stone, the latter is perhaps preferable. 



Igneous and siliceous rocks, though often hard, do not consolidate so 

 well or so quickly as limestone, owing to the sandy, detritus formed by 

 the first two having no cohesion. The detritus of magnesian limestone 

 acts like a mortar. 



The most efficient and economic road metals are diabase and syenite. 

 Granite and gneiss, specially if very micaceous, are apt to disintegrate 



