Description of the Great Chimney at St Rollox. 217 
Total height from foundations, : 447 feet 6 in. 
Depth of foundations, 2 : : Gi cote teas 
Total height above the surface, 432 feet 6 in. 
Diameter at base, . 45 feet. 
surface, 40 ... 
top, . 18 feet 6 in. 
There are used in its construction 1,250,000 bricks of 
first quality, weighing 121 lb. per cubic foot, resisting 63 
tons’ pressure per superficial foot before cracking, and re- 
quiring 110 tons to crush them. The brick-work is 34 bricks 
at bottom, and1}attop. The internal flue is 260 feet high, 
and is perfectly vertical. 
It took six months, in two different seasons, autumn 1841, 
and spring 1842, to build it, which was accomplished without 
the slightest accident. It was finished in June 1842. 
In May 1844, a rent was discovered in one side, about 
36 feet long, extending, from a point about 100 feet from the 
top, downwards. This rent was affirmed by some to have 
been caused by lightning. The rent gradually increased 
during June and July, and then a similar rent was discovered 
on the opposite side, beginning somewhat lower down than 
that first observed, but extending only 45 feet. This created 
some apprehension; and, in August, it was determined to 
examine the chimney where the rents appeared, and, accord- 
ing to the result of this examination, to proceed to measures 
of security or of protection. Scaffolding appeared at first 
the only means of effecting the desired examination, without 
stopping the works. Balloons were afterwards proposed, 
but were considered not so likely a means of accomplishing 
the end in view, although the celebrated Mr Green, on being 
applied to, offered the use of a balloon, and his own personal 
superintendence of the ascent. During the erection of the 
chimney, in 1841,—while Mr Colthurst, civil-engineer, was 
superintending the laying of the foundations, and erection of 
the first 80 feet of the great chimney,—an accident occurred 
to a chimney of a cotton-factory in the neighbourhood of St 
- Rollox, which rendered it highly desirable that some one 
should go to the top of the chimney. Scaffolding would have 
cost L.20. Mr Colthurst suggested that, by driving staples 
into the joints of the brick-work, a man might be able to 
