x: 
80 
in its application to mere construction, whether it be of a mili- 
tary or civil work) was yet in its infancy in this country. 
Our resources in building materials were almost unknown, 
their qualities and adaptabilities to different purposes of 
construction undeveloped. ‘Thus far the matter had excited 
little attention ; the building material, whether brick or stone, 
lime or timber, nearest at hand was indiscriminately used, 
and its aggregation left much to the skill of the mechanic. In 
commencing constructions on so great a scale, it was of the 
first importance that the work should be both durable and 
economical; a result only to be attained by the most careful 
selection of materials, and the most skilful manipulation. 
Besides, our forts called for arrangements unknown in -_ 
branches of building, — arrangements for which the execution 
and the most suitable materials had to be studied out ab 
tnitio, since on many of these points there were neither 
experience nor extant rules to guide. 
In the years 1830 and 1831 a series of experiments wa® 
instituted by Colonel Totten at Fort Adams, on the e* 
pansion and contraction of. building stone by natural 
changes of temperature, and the effects of these variations 
on the cements employed to secure the joints of ston? 
copings. An account of them was prepared under his di- 
rection by Lieutenant (now Professor) W. H. C. Bartlett, 
a member of this Academy, and published in the America" 
Journal of Science for July, 1832. The methods employed 
were at once simple and ingenious, and the result was 
as to leave no doubt that in this climate the joints of coping 
formed of stone of four or five feet in length will always be 
insecure, no matter what description of cement may be ¢™ 
ployed to close them. 
ly to the experimental examination of the subject by Colonel 
a 
