36 ANNUAL REPORT 
6. The variations in the size of the grains of sand, or the percent- 
age of voids, determines the amount of loam which can be added. 3 
Comparing the sands used, the conclusion was, that the difference in 
strength shown by the several mixtures was due, largely, to the resulting 
density of the mortars. 
7. The writer came to the conclusion after carefully weighing the 
evidence of the diagrams, that a mortar*with 24 per cent. of loam in the 
sand is about the highest safe limit for Giant cement, while about 21 to 
24 per cent. is the limit for Atlas cement. 
The temperature diagram shows that the minimum temperature dur- 
ing the day was below freezing during most of the time of the first four 
months of the tests, while the maximum temperature was below freezing 
58 days out of go. 
The precipitation was slightly. above normal. 
COLORED MORTARS. 
Colored‘mortars are used for various purposes. Mortar for pointing 
is colored to match the brick or stone masonry or else in contrast to set the 
joint in relief. Concrete building stones are colored red, ‘terra cotta, 
brown, or slate to resemble different natural building stones. Cement 
sidewalk surfaces are colored slate, black or brown to prevent the glare 
of light which the uncolored cement surfaces ‘reflect. Physicians have 
claimed that the great prevalence of ophthalmia and other forms of weak 
eyes is frequently due to the blinding glare from cement paved walks and 
limestone paved roads. At any’‘rate, it is well known that uncolored pave- 
ments are very taxing on the eyes during bright, clear weather. 
Mosaic and tile work are now manufactured from cement by using 
certain coloring materials. The cement sets very hard and permits a high 
polish. No coloring containing acids or anything that will act upon the 
alkalies in the cement can be used. Vegetable or oil colors destroy or 
impair the strength of the cement. Dry mineral colors affect cement the 
least, although, with the exception of ultramarine, which contains much 
silica, all coloring materials reduce the strength and durability of cement 
mortar to a greater or less degree. Ultramarine in small quantities seems 
to strengthen the mortar slightly. 
The iron oxides and ochres are used for all shades ranging from 
yellow to red and brown; Manganese dioxide and lamp-black for grays, 
slates and blacks; and ultramarines for the greens and blues. Manganese 
dioxide is better for slates and blacks than lamp-black, as the oil in the 
latter affects the strength of the mortar. 
Several tables giving the materials to use for different colors with 
the proportions to be used are condensed and given below. Column 
number one is taken from a leaflet on Portland cement by the Buckeye 
Portland Cement Company; number two is taken from C. C. Brown’s 
