4 
masonry, which is (as I have said) different in kind ; nearly 
all the larger cracks do however extend quite through the 
walls, producing loose work inside, and bursting out the 
surfaces of dressed stone on the exterior. 
By inserting long bond stones across these fractures, as 
high up as they can be traced; by bonding the walls to 
each other at all the interior angles ; and by the iron plates 
proposed to be used as bonds, the walls will I believe be 
far better calculated to resist pressure than when they were 
erected. 
A third great cause of evil, has been the decay of the 
sand stone, with which the plain faces of the exterior of the 
Tower were built. This stone is evidently quarried not 
far from the town, probably at Norton or Bradford, and 
forms one variety of the “new red sand stone group.” It 
seems generally to have been well selected, and is very 
hard and compact where not decayed. It is at the angles 
and buttresses, that the decomposition has become so se- 
rious, and wherever the stone has been exposed on more 
than one side to the action of the weather. All these ex- 
posed parts must be re-built with the more durable stone 
from the Hamden Hill quarries. This latter material is 
that with which all the ornamental features of the Tower 
are constructed, including the parapet and pinnacles, the 
windows, string courses, arches, &c. It belongs to the 
class of “inferior oolites,” and ranks high as material for 
building. The quarries were worked by the Romans, at a 
very early period. There is a great difference in the 
quality of the beds. The best: stone being whiter and 
more expensive to work from its hardness and closer tex- 
ture. This has led to the use of the inferior stone in great 
quantity, until an opinion has prevailed that the better beds 
were exhausted. It is certain however, that excellent stone 
can yet be obtained by paying a rather higher price for it. 
In St. Mary’s Tower, there is alarge amount of good stone 
little injured by the wear of 350 years. Unless laid in its 
bed, that is, wıth the grain or strata of the stone horizon- 
tally as dug from the quarry, it however will not endure 
either weather or vertical pressure long, and the decay ofthe 
Ham Hill stone work throughout the Tower, is limited by 
the extentto which it has been used with a vertical bed. Un- 
fortunately nearly all the prominent features have suffered 
from this cause. "The jambs of the windows are generally 
