3 1 8 
REVUE DES QUESTIONS SCIENTIFIQUES. 
I shall say little ; for. with ail their evils, lhey add to our expe- 
rimental knowledge, and convey a lesson, though a costly one. 
But a class of structures fraugkt with rnuch grealer evils exists 
in yreat abundcince throughout the country : uaniely, tliose 
in which the faults of an unseientific design hâve been so far 
counteracted by massive strength, good materials. and careful 
workmanship, that a temporary stability lias been produced, but 
which contain within themselves sources of weakness, obvious 
to a scientific examination only, that must inevitably cause their 
destruction, within a liniited uumber of years (p. 6). „ 
