82 TRANSACTIONS OF THE PLYMOUTH INSTITUTION. 
The way itself consists of two parallel lines of granite blocks, 
each line having a rebate worked along its outer half. The 
gauge, or distance between the rebates, is exactly four feet. The 
depth of the rebate varies in places from three to six inches, 
and the action is precisely similar to that of the Coalbrookdale 
cast-iron rail 8, and very like that of the check or guard rail 
now fitted to lines on sharp curves or at crossings. The horizontal 
portion of the rebate carried the weight, while the vertical portion 
bore against the inner circumference of the wheel, and kept it 
in its place. 
At one place at Bovey rails of iron almost precisely similar 
to the Coalbrookdale pattern have been used, where the line 
crosses a stream by means of a wooden bridge. At curves the 
stones do not seem to have been dressed to form, but short, straight 
stones were worked in, which by the constant friction of the 
wheels soon wore down to a sufficiently accurate shape. The stones 
vary much in all dimensions, but perhaps an average block would 
be four feet long and one foot six inches square ; many of them 
are as long as seven feet. Points and crossings were formed 
in large blocks by working grooves six inches wide and two 
or three inches deep. At no place was any serious cutting or 
embankment attempted, for the greater part both being only such 
as were necessary to carry the road along the inclined face of 
a hill. No attempt was anywhere made to bond together or 
connect the stones. 
The reason for the substitution of granite for iron in this 
tramway is of course evident. Where granite was to be had 
for the cost of production, it is not surprising that as a material 
it should have been adopted. And it does not follow that because 
the material was cheaper it was necessarily inferior. The cast- 
iron rails at that time in vogue were a constant source of annoy- 
ance and expense, invariably giving way at the wrong moment, 
and being very uncertain in their general behaviour when heavily 
laden. Now the Heytor granite is an exceptionally good material, 
and the granite-way as laid was far superior in many respects 
to the cast-iron rail. This tramway was thoroughly efficient, and 
quite up to its work ; for the two large blocks of granite having 
the city arms upon them, at either end of London Bridge, came 
from the Heytor quarries over this line to Stover, and were 
thence shipped to London. The Waithman monument, in Ludgate 
