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On the Expansion of different kinds of Stone from an increase of 
Temperature, with a Description of the Pyrometer used in 
making the Experiments. By Avexanprer J. Avr, Civil 
Engineer. 
(Read 20th April 1835.) 
For a long time I was anxious to know the rate of expan- 
sion of the common building-stone of this neighbourhood, as it 
is not given in any of the tables of the expansions of substances, 
because I have sometimes thought that the vertical cracks fre- 
quently seen intersecting rubble walls might arise from the con- 
traction caused by a diminution of temperature. During a long- 
continued and severe frost which occurred in 1826, I thought 
the rents in a considerable stretch of wall, which I passed at all 
seasons, appeared more open than usual. This, however, was 
merely conjectural, and I paid no more attention to the subject 
until 1830, when, as I mentioned in a notice on the commencement 
of my experiments read at the meeting of the British Association 
in September last, an interdict of the Dean of Guild Court of 
Edinburgh rendered the rate of expansion of stone a matter of 
more importance than merely a curious philosophical speculation. 
The interdict was issued against a gentleman who wished to alter 
his property, by supporting the front on cast-iron pillars, in the 
manner now commonly followed in this city in converting the 
ground-floor of dwelling-houses into shops. The front of the pre- 
mises alluded to was narrow, and of a great height; and the reasons 
given for interdicting the operations were, that the pillars had 
not sufficient strength to support the weight of the front, and 
that the difference of the expansion of cast-iron and stone was so 
great, that very prejudicial effects might arise from the use of 
such pillars in this situation. Mr Jarping, civil engineer, was 
