badd 
81 
Totten, the walls of our most expensive works of masonry 
were protected by copings cemented at their joints; and 
while the failure of the cement was constantly noticed, the 
cause of the failure was not understood. The experiments 
showed that the changes of longitudinal dimensions of granite 
coping-stones, five feet only in length, under the extreme 
temperatures to which they were exposed at Newport, would 
be sufficient to pulverize the hardest cement between them, 
or to leave cracks in it thicker than common pasteboard. 
With marble as a material, these destructive effects are con- 
siderably increased, and with sandstone, nearly doubled. 
About the same time, Colonel Totten caused some experi- 
ments to be made to ascertain the relative stiffness and 
strength of the following kinds of timber, viz. White Pine, 
(Pinus strobus), Spruce (Abies nigra), and Southern Pine 
(Pinus australis), also called Long-leaved Pine. 
These experiments, made by his assistant, Lieutenant Re, 
S. Brown,’of the Corps of Engineers, were published in the 
American Journal of Science and Art, and afterwards, hav- 
ing been revised by the author, in the Journal of the Frank- 
lin Institute, a note being added, the calculations extended, 
and practical inferences drawn therefrom. This memoir and 
additions are found in Vol. VIL., new series, Journal of the 
Franklin Institute, 1831. Lieutenant Brown’s account con- 
cludes with the following remarks : — 
“In Tredgold’s carpentry, and other similar works, may 
be found the constant numbers (a) and (c) for nearly all the 
kinds of wood useful in the arts; but besides that the num- 
bers are in many instances calculated from insufficient ex-~ 
periments, most of the specimens used in the trials were 
of European growth, and of course the results obtained are 
inapplicable to American timber, though bearing the same 
Rame. Itis much to be desired that numerous and accurate 
i 
