Mortar . 
269 
mon attraction of aggregation or cohesion. I conceive 
each of these to be distinct. 
Hence it is essential to good mortar, 1st. that the lime 
be burnt so as to reduce twenty parts by weight to eleven 
parts. 2d. That it be used as quickly as possible. 3d. 
That if it cannot be used quickly, it should be packed up 
when slacked in the smallest possible compass, and cover- 
ed from the contact of successive changes of air. 4th„ 
That to fresh lime, seven parts of sand are not too much : 
lime half burnt will not cement more than three parts. 
Hence the threefold extravagance of not using lime in a 
proper state : the lime is wasted : the weight of carriage 
is increased by hauling limestone instead of lime : and 
more lime is required to the same quantity of sand. 
Though not essential to good building, it is very nearly 
so, that the brick (always supposed to be well burnt) 
should be dipt in lime water the instant before it is laid. 
The dust on a dry brick effectually prevents the adhesion 
of the mortar ; and the brick also absorbs so much of the 
moisture of the mortar, that enough is not left to enable it 
perfectly to crystallize. Immersing the brick in lime 
water, makes it also less liable to imbibe moisture. It 
forms an impregnation of limestone. 
When the lime is good, no addition of skimmed milk, 
animal gelly, oil, or resinous substances, or any other, 
contributes to the goodness of the mortar : good lime, 
5 good sand, are the only requisites. 
The putting beams and rafters, or any other method ©f 
shaking the wall, and greatly disturbing the crystalliza- 
tion of the mortar while damp, injures its power as a ce- 
ment. 
In countries where limestone and fuel are plenty, and 
labour cheap, the ancient method of building walls by 
grouting , may be eligible. It is this : 
