In common practice, the cohesion of mortar is greatly impaired by using too large a proportion of sand ; it should never exceed two parts, by measure, to one of lime paste. A cask of lime weighing 280 Ibs., made into eight cubic feet of lime paste, should be mixed with 16 bush els of damp sand. The notion used to be generally entertained that the longer lime was slaked before it was used, the better would be the mortar made of it. This, however, is not the case with our common fat lime and sand mortars. The sand should be mixed with the slaked lime as soon as the latter becomes cold, and no more water should be employed than will reduce the lime to a thick paste. In preparing mortar the unslaked lime should be placed on boards and sheltered f^^m t he sun and rains ; it should be open above and sunounded with some sand. The water necessary to slake lime should be poured upon it with any suitable vessel, and care should be taken to stir the lime so as to bring the water into contact with every portion, when it may be left until all the vapoi- has passed off. The sand may now be incorporated wi'tIl the lime by means of a hoe and shovel ; and, if necessary, a little water may be added to produce a homogeneous consistent paste. when it is ready for use. Sand from the sea shore should never be employ ed for making mortar without being first washed with fresh water, because the salt left in such sand is li able to absorb moisture and prevent the mortar becoming hard. In putting up walls of brick or stone, care should be taken that the stones or bricks be moistened before they come in contact with the mortar. Every brick and stone should be laid in a good bed of mortar, and should receive a blow to fix it firmly. The bricks should not be laid merely as is the common custom, but forced down so as to press the mortar into all the pores and crevices. The superintendent of a building should give his personal attention. to the vertical joints in walls, as the masons frequently neglect to fill them up with mortar. THE ancients in hauling the large stones to erect the pyramids used to build inclined causeways on which they transported the huge blocks.