All mason-work below ground should be laid in cement mortar, and all arches or heavily loaded piers as well. In many city laws, the use of cement mortar is required to a certain proportion of the height of wall. Cement mortar of some kind should he used for setting cornice stones and wherever the work is especially exposed. For all work under water, for large arches and for tops of chimneys, Portland cement should he used, and Portland cement may he mixed with Rosendale to make a strong, quick-setting mortar. Portland cement and lime may he mixed to give a strong light-colored mortar which is much used in England for face-brick work.

Fig. 116. Arch of Stretchers.

Fig. 116. Arch of Stretchers.

Fig. 117. Bonded Stretchers in Arch.

Fig. 117. Bonded Stretchers in Arch.