26$ Mortar . 
Lime ought to be brought from the kiln, in a cart co- 
vered with boards. 
It ought not to be brought in rainy weather. I have 
twice or thrice seen carts set on fire by this means. It 
ought to be kept in a dry place, with the precautions be- 
fore mentioned. The neat rule is, expose it to the air as 
little as possible. 
When the limestone is so good, and the burning is so 
complete, that twenty parts of limestone is fairly burnt 
into eleven parts of lime, which it can be and ought to be — 
then will such lime, used as recently as possible, require 
seven parts of sand to one of lime, to make the best mortar. 
It will require less sand in proportion as it is badly 
burnt, or by negligent exposure reconverted into limestone. 
Nothing is required, to make the best mortar for build- 
ing, but good lime and good sand. 
No sand is good that contains any clay. It should be 
washed out. 
No sand is good, that is rounded by attrition. 
The best sand is quartzose, having fiat sides and an- 
gles. 
The best mixture of such sand, is half somewhat coarse, 
half fine : not too fine, for ground or powdered quartz, 
or hint may do for stucco, but not for mortar : the flat 
sides and angles are destroyed by the pulverization. 
The theory of mortar appears to me to be this. Water 
is added, to enable the lime to crystallize, and to attract 
carbonic acid from the atmosphere. This is done gradu- 
ally. If left quietly and undisturbed, to regain this gas 
from the atmosphere, the mortar crystallizes into lime- 
stone, and unites by the attraction of crystallization to 
the sides of the quartzose sand, best calculated to afford 
the strongest union or adhesion. The attraction is three- 
fold, 1st. that of crystallization : 2d. that of chemical or 
elective attraction in the moist way ; and 3d® the com- 
