Mr. Walker exposed the undermentioned descriptions of granite and whinstone to very heavy waggon traffic for seventeen months, and found their vertical wear to be as follows :-


Guernsey granite


Herm ,,


Baltic whinstone


Peterhead blue granite .



Heytor granite


Aberdeen red granite .


Dartmoor granite


Aberdeen blue granite .


Mr. Newton's experiments on the flags used in Liverpool showed Kilrush flags to be most durable, Caithness flags next. The flags found to be least durable were those from Llangollen and Yorkshire.1

1 D. Kinnear Clarke On Roads and Streets.